Trial Outcomes & Findings for Jump-In: Building Better Bones (NCT NCT00729378)

NCT ID: NCT00729378

Last Updated: 2025-10-28

Results Overview

Baseline to 12-month change in trabecular bone area at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: square millimeters (mm\^2).

Recruitment status

COMPLETED

Study phase

NA

Target enrollment

509 participants

Primary outcome timeframe

Baseline to 12-months

Results posted on

2025-10-28

Participant Flow

Recruitment was performed for three years (2007-2009) in a total of 16 elementary and middle schools (9 intervention and 7 control) in two Tucson, Arizona area school districts. Recruitment consisted of attending back to school days and holding recruitment assemblies before or after school.

Intervention and control schools designated prior to recruiting. Schools were selected based on size, demographics, and student flow from elementary to middle school to prevent contamination. 739 participants completed informed consent process (agreed to participate); only 509 scheduled measurement appointments and completed study measurements.

Participant milestones

Participant milestones
Measure
Exercise Intervention
Subjects in the exercise intervention arm performed activities designed to provide skeletal loading: impact activities, 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Control
Subjects in the control arm did not take part in intervention exercises. Physical activity performed by these subjects was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline
STARTED
430
309
Baseline
COMPLETED
292
217
Baseline
NOT COMPLETED
138
92
12-months
STARTED
292
217
12-months
COMPLETED
192
152
12-months
NOT COMPLETED
100
65
24-months
STARTED
192
152
24-months
COMPLETED
120
101
24-months
NOT COMPLETED
72
51
36-months
STARTED
120
101
36-months
COMPLETED
105
95
36-months
NOT COMPLETED
15
6

Reasons for withdrawal

Reasons for withdrawal
Measure
Exercise Intervention
Subjects in the exercise intervention arm performed activities designed to provide skeletal loading: impact activities, 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Control
Subjects in the control arm did not take part in intervention exercises. Physical activity performed by these subjects was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline
Did not complete study measurements
72
33
Baseline
Withdrawal by Subject
66
59
12-months
Lost to Follow-up
100
65
24-months
Lost to Follow-up
72
51
36-months
Lost to Follow-up
15
6

Baseline Characteristics

Jump-In: Building Better Bones

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure
Exercise Intervention
n=292 Participants
Subjects in the exercise intervention arm performed activities designed to provide skeletal loading: impact activities, 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Control
n=217 Participants
Subjects in the control arm did not take part in intervention exercises. Physical activity performed by these subjects was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Total
n=509 Participants
Total of all reporting groups
Age, Continuous
10.6 years
STANDARD_DEVIATION 1.1 • n=5 Participants
10.7 years
STANDARD_DEVIATION 1.0 • n=7 Participants
10.7 years
STANDARD_DEVIATION 1.1 • n=5 Participants
Sex: Female, Male
Female
292 Participants
n=5 Participants
217 Participants
n=7 Participants
509 Participants
n=5 Participants
Sex: Female, Male
Male
0 Participants
n=5 Participants
0 Participants
n=7 Participants
0 Participants
n=5 Participants
Ethnicity (NIH/OMB)
Hispanic or Latino
67 Participants
n=5 Participants
50 Participants
n=7 Participants
117 Participants
n=5 Participants
Ethnicity (NIH/OMB)
Not Hispanic or Latino
225 Participants
n=5 Participants
167 Participants
n=7 Participants
392 Participants
n=5 Participants
Ethnicity (NIH/OMB)
Unknown or Not Reported
0 Participants
n=5 Participants
0 Participants
n=7 Participants
0 Participants
n=5 Participants
Race (NIH/OMB)
American Indian or Alaska Native
1 Participants
n=5 Participants
2 Participants
n=7 Participants
3 Participants
n=5 Participants
Race (NIH/OMB)
Asian
20 Participants
n=5 Participants
11 Participants
n=7 Participants
31 Participants
n=5 Participants
Race (NIH/OMB)
Native Hawaiian or Other Pacific Islander
2 Participants
n=5 Participants
1 Participants
n=7 Participants
3 Participants
n=5 Participants
Race (NIH/OMB)
Black or African American
11 Participants
n=5 Participants
3 Participants
n=7 Participants
14 Participants
n=5 Participants
Race (NIH/OMB)
White
254 Participants
n=5 Participants
196 Participants
n=7 Participants
450 Participants
n=5 Participants
Race (NIH/OMB)
More than one race
2 Participants
n=5 Participants
0 Participants
n=7 Participants
2 Participants
n=5 Participants
Race (NIH/OMB)
Unknown or Not Reported
2 Participants
n=5 Participants
4 Participants
n=7 Participants
6 Participants
n=5 Participants
Region of Enrollment
United States
292 Participants
n=5 Participants
217 Participants
n=7 Participants
509 Participants
n=5 Participants

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of total volumetric bone density at the femur 4% site. Measurement made by peripheral quantitative computed tomography (pQCT) at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Total Volumetric Bone Density at the Femur 4% Site
270.79 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 32.97
277.25 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 33.83

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of trabecular bone at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Volumetric Bone Density of Trabecular Bone at the Femur 4% Site
232.34 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 31.56
239.32 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 32.2

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of Cortical bone at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Volumetric Bone Density of Cortical Bone at the Femur 4% Site
267.89 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 30.75
273.80 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 31.23

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of trabecular bone area at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: square millimeters (mm\^2).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Trabecular Bone Area at the Femur 4% Site
1053.15 millimeters squared (mm^2)
Standard Deviation 227.32
1039.55 millimeters squared (mm^2)
Standard Deviation 220.17

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of cortical bone area at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: square millimeters (mm\^2).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Cortical Bone Area at the Femur 4% Site
1348.65 millimeters squared (mm^2)
Standard Deviation 284.24
1335.56 millimeters squared (mm^2)
Standard Deviation 274.22

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of periosteal circumference at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Periosteal Circumference at the Femur 4% Site
125.63 millimeters (mm)
Standard Deviation 12.50
124.91 millimeters (mm)
Standard Deviation 12.42

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of bone strength index (BSI) at the femur 4% site. Bone Strength Index (BSI) is a measurement of the resistance to compression forces at the epiphyses of long bones. Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: mm\^4.

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Bone Strength Index at the Femur 4% Site
93.52 mm^4
Standard Deviation 27.39
96.77 mm^4
Standard Deviation 28.00

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of total volumetric bone density at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Total Volumetric Bone Density at the Femur 20% Site
478.72 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 60.59
489.70 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 63.98

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of trabecular bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Volumetric Bone Density of Trabecular Bone at the Femur 20% Site
153.11 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 36.77
163.81 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 39.43

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of Cortical bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Volumetric Bone Density of Cortical Bone at the Femur 20% Site
1045.20 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 23.07
1046.01 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 22.27

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of periosteal circumference at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Periosteal Circumference at the Femur 20% Site
77.78 millimeters (mm)
Standard Deviation 8.66
77.43 millimeters (mm)
Standard Deviation 8.56

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of cortical thickness at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Cortical Thickness at the Femur 20% Site
2.50 millimeters (mm)
Standard Deviation .35
2.52 millimeters (mm)
Standard Deviation .37

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of stress-strain index at the femur 20% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: mm\^3.

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Stress-Strain Index at the Femur 20% Site
1344.66 mm^3
Standard Deviation 399.31
1340.19 mm^3
Standard Deviation 404.78

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of trabecular bone at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Volumetric Bone Density of Trabecular Bone at the Tibia 4% Site
219.74 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 25.56
224.03 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 27.58

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of total volumetric bone density at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Total Volumetric Bone Density at the Tibia 4% Site
291.62 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 33.17
297.27 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 37.02

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of cortical bone at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Volumetric Bone Density of Cortical Bone at the Tibia 4% Site
291.93 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 31.92
297.40 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 35.63

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of trabecular bone area at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: square millimeters (mm\^2).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Trabecular Bone Area at the Tibia 4% Site
475.80 millimeters squared (mm^2)
Standard Deviation 108.85
467.73 millimeters squared (mm^2)
Standard Deviation 100.86

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of cortical bone area at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: square millimeters (mm\^2).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Cortical Bone Area at the Tibia 4% Site
625.57 millimeters squared (mm^2)
Standard Deviation 127.11
617.19 millimeters squared (mm^2)
Standard Deviation 117.67

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of periosteal circumference at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Periosteal Circumference at the Tibia 4% Site
86.43 millimeters (mm)
Standard Deviation 8.82
85.86 millimeters (mm)
Standard Deviation 8.36

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of bone strength index (BSI) at the tibia 4% site. Bone Strength Index (BSI) is a measurement of the resistance to compression forces at the epiphyses of long bones. Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: mm\^4.

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Bone Strength Index at the Tibia 4% Site
51.03 mm^4
Standard Deviation 13.63
52.45 mm^4
Standard Deviation 15.15

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of total volumetric bone density at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Total Volumetric Bone Density at the Tibia 50% Site
736.33 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 58.07
745.69 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 59.54

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of trabecular bone at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Volumetric Bone Density of Trabecular Bone at the Tibia 50% Site
131.63 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 26.97
137.39 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 26.83

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of cortical bone at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Volumetric Bone Density of Cortical Bone at the Tibia 50% Site
1070.95 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 31.93
1070.32 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 32.88

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of periosteal circumference at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Periosteal Circumference at the Tibia 50% Site
62.33 millimeters (mm)
Standard Deviation 5.83
61.98 millimeters (mm)
Standard Deviation 5.43

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of cortical thickness at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Cortical Thickness at the Tibia 50% Site
4.00 millimeters (mm)
Standard Deviation .54
4.05 millimeters (mm)
Standard Deviation .58

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of stress-strain index at the tibia 50% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: mm\^3.

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Stress-Strain Index at the Tibia 50% Site
1023.74 mm^3
Standard Deviation 297.42
1004.97 mm^3
Standard Deviation 272.40

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of total volumetric bone density at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Total Volumetric Bone Density at the Tibia 66% Site
552.71 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 61.05
566.04 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 63.11

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of trabecular bone at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Volumetric Bone Density of Trabecular Bone at the Tibia 66% Site
152.34 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 28.73
159.04 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 30.48

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of volumetric bone density of cortical bone at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Volumetric Bone Density of Cortical Bone at the Tibia 66% Site
1026.07 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 31.38
1029.42 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 32.92

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of periosteal circumference at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Periosteal Circumference at the Tibia 66% Site
72.34 millimeters (mm)
Standard Deviation 7.25
71.55 millimeters (mm)
Standard Deviation 6.53

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of cortical thickness at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Cortical Thickness at the Tibia 66% Site
3.02 millimeters (mm)
Standard Deviation .46
3.06 millimeters (mm)
Standard Deviation .49

PRIMARY outcome

Timeframe: Baseline

Population: Population consists of all participants that had complete measurements at the baseline time point (N = 503; Age = 10.6 +/- 1.1 yrs; Height = 144.5 +/- 9.7 cm; Weight = 39.2 +/- 10.5 kg).

Baseline (initial) measurement of strength-strain index at the tibia 66% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: mm\^3.

Outcome measures

Outcome measures
Measure
Control
n=217 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=286 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
Baseline Stress-Strain Index at the Tibia 66% Site
1187.31 mm^3
Standard Deviation 353.09
1167.94 mm^3
Standard Deviation 331.61

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in total volumetric bone density at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Total Volumetric Bone Density the Femur 4% Site
2.83 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 12.32
3.10 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 15.36

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of trabecular bone at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Volumetric Bone Density of Trabecular Bone at the Femur 4% Site
5.89 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 12.94
3.37 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 15.23

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of cortical bone at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Volumetric Bone Density of Cortical Bone at the Femur 4% Site
1.68 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 11.47
2.14 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 14.47

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in trabecular bone area at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: square millimeters (mm\^2).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Trabecular Bone Area at the Femur 4% Site
144.97 millimeters squared (mm^2)
Standard Deviation 96.38
104.16 millimeters squared (mm^2)
Standard Deviation 111.80

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in cortical bone area at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: square millimeters (mm\^2).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Cortical Bone Area at the Femur 4% Site
185.50 millimeters squared (mm^2)
Standard Deviation 119.42
140.00 millimeters squared (mm^2)
Standard Deviation 131.17

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in periosteal circumference at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Periosteal Circumference at the Femur 4% Site
8.09 millimeters (mm)
Standard Deviation 4.84
6.17 millimeters (mm)
Standard Deviation 5.80

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in bone strength index (BSI) at the femur 4% site. Bone Strength Index (BSI) is a measurement of the resistance to compression forces at the epiphyses of long bones. Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: mm\^4.

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Bone Strength Index at the Femur 4% Site
15.03 mm^4
Standard Deviation 14.19
12.84 mm^4
Standard Deviation 12.67

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in total volumetric bone density at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Total Volumetric Bone Density at the Femur 20% Site
-2.46 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 18.74
2.40 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 22.38

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of trabecular bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Volumetric Bone Density of Trabecular Bone at the Femur 20% Site
5.77 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 12.38
7.12 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 12.98

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of cortical bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Volumetric Bone Density of Cortical Bone at the Femur 20% Site
4.39 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 19.38
6.87 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 20.02

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in thickness of cortical bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Thickness of Cortical Bone at the Femur 20% Site
.11 millimeters (mm)
Standard Deviation .15
.11 millimeters (mm)
Standard Deviation .17

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in periosteal circumference at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Periosteal Circumference at the Femur 20% Site
5.65 millimeters (mm)
Standard Deviation 2.20
4.89 millimeters (mm)
Standard Deviation 2.21

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in strength-strain index at the femur 20% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: mm\^3.

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Stress-Strain Index at the Femur 20% Site
297.43 mm^3
Standard Deviation 145.31
261.94 mm^3
Standard Deviation 137.73

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in total volumetric bone density at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Total Volumetric Bone Density at the Tibia 4% Site
10.34 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 19.34
9.87 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 17.29

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of trabecular bone at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Volumetric Bone Density of Trabecular Bone at the Tibia 4% Site
2.36 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 9.33
2.84 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 10.22

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of cortical bone at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Volumetric Bone Density of Cortical Bone at the Tibia 4% Site
10.10 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 18.73
9.69 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 16.76

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in trabecular bone area at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: square millimeters (mm\^2).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Trabecular Bone Area at the Tibia 4% Site
24.65 millimeters squared (mm^2)
Standard Deviation 50.00
29.87 millimeters squared (mm^2)
Standard Deviation 52.91

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in cortical bone area at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: square millimeters (mm\^2).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Cortical Bone Area at the Tibia 4% Site
39.53 millimeters squared (mm^2)
Standard Deviation 49.12
44.85 millimeters squared (mm^2)
Standard Deviation 54.14

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in periosteal circumference at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Periosteal Circumference at the Tibia 4% Site
2.77 millimeters (mm)
Standard Deviation 3.44
3.17 millimeters (mm)
Standard Deviation 3.70

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in bone strength index (BSI) at the tibia 4% site. Bone Strength Index (BSI) is a measurement of the resistance to compression forces at the epiphyses of long bones. Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: mm\^4.

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Bone Strength Index at the Tibia 4% Site
7.46 mm^4
Standard Deviation 5.53
7.84 mm^4
Standard Deviation 5.39

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in total volumetric bone density at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Total Volumetric Bone Density at the Tibia 50% Site
17.76 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 22.02
17.98 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 22.27

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of trabecular bone at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Volumetric Bone Density of Trabecular Bone at the Tibia 50% Site
-3.16 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 15.63
-2.74 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 13.55

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of cortical bone at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Volumetric Bone Density of Cortical Bone at the Tibia 50% Site
11.16 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 18.91
14.34 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 22.23

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in periosteal circumference at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Periosteal Circumference at the Tibia 50% Site
3.11 millimeters (mm)
Standard Deviation 1.09
2.98 millimeters (mm)
Standard Deviation 1.33

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in cortical thickness at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Cortical Thickness at the Tibia 50% Site
.31 millimeters (mm)
Standard Deviation .20
.29 millimeters (mm)
Standard Deviation .20

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in strength-strain index at the tibia 50% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: mm\^3.

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Stress-Strain Index at the Tibia 50% Site
185.36 mm^3
Standard Deviation 79.04
171.82 mm^3
Standard Deviation 68.00

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in total volumetric bone density at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Total Volumetric Bone Density at the Tibia 66% Site
9.58 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 29.98
7.00 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 32.41

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of trabecular bone at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate.Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Volumetric Bone Density of Trabecular Bone at the Tibia 66% Site
2.08 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 14.64
3.40 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 13.49

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in volumetric bone density of cortical bone at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=9 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Volumetric Bone Density of Cortical Bone at the Tibia 66% Site
12.69 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 21.32
11.63 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 24.00

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in periosteal circumference at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Periosteal Circumference at the Tibia 66% Site
3.79 millimeters (mm)
Standard Deviation 2.06
3.69 millimeters (mm)
Standard Deviation 2.35

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in cortical thickness at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Cortical Thickness at the Tibia 66% Site
.18 millimeters (mm)
Standard Deviation .22
.17 millimeters (mm)
Standard Deviation .21

PRIMARY outcome

Timeframe: Baseline to 12-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 12-month change in strength-strain index at the tibia 66% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: mm\^3.

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
12-month Change in Stress-Strain Index at the Tibia 66% Site
228.46 mm^3
Standard Deviation 103.48
214.93 mm^3
Standard Deviation 96.58

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in total volumetric bone density at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units mg/ccm.

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month in Change in Total Volumetric Bone Density the Femur 4% Site
13.47 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 19.09
13.70 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 22.89

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of trabecular bone at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month in Change in Volumetric Bone Density of Trabecular Bone at the Femur 4% Site
8.23 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 16.35
8.03 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 19.34

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of cortical bone at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month in Change in Volumetric Bone Density of Cortical Bone at the Femur 4% Site
10.78 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 17.95
10.67 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 21.83

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in trabecular bone area at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: square millimeters (mm\^2).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Trabecular Bone Area at the Femur 4% Site
178.04 millimeters squared (mm^2)
Standard Deviation 146.00
160.89 millimeters squared (mm^2)
Standard Deviation 158.53

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in cortical bone area at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: square millimeters (mm\^2).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Cortical Bone Area at the Femur 4% Site
255.67 millimeters squared (mm^2)
Standard Deviation 165.23
237.12 millimeters squared (mm^2)
Standard Deviation 178.61

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in periosteal circumference at the femur 4% site . Measurement made by pQCT at a distance of 4% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Periosteal Circumference at the Femur 4% Site
10.72 millimeters (mm)
Standard Deviation 6.88
10.08 millimeters (mm)
Standard Deviation 7.73

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in bone strength index (BSI) at the femur 4% site. Bone Strength Index (BSI) is a measurement of the resistance to compression forces at the epiphyses of long bones. Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: mm\^4.

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Bone Strength Index at the Femur 4% Site
27.81 mm^4
Standard Deviation 17.76
28.08 mm^4
Standard Deviation 17.51

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in total volumetric bone density at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Total Volumetric Bone Density at the Femur 20% Site
15.36 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 28.47
14.88 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 31.73

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of trabecular bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Volumetric Bone Density of Trabecular Bone at the Femur 20% Site
9.04 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 13.87
11.83 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 17.20

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of cortical bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Volumetric Bone Density of Cortical Bone at the Femur 20% Site
22.26 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 29.62
21.56 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 29.46

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in thickness of cortical bone at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Thickness of Cortical Bone at the Femur 20% Site
.31 millimeters (mm)
Standard Deviation .21
.27 millimeters (mm)
Standard Deviation .22

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in periosteal circumference at the femur 20% site . Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Periosteal Circumference at the Femur 20% Site
9.29 millimeters (mm)
Standard Deviation 3.08
8.25 millimeters (mm)
Standard Deviation 3.38

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in strength-strain index at the femur 20% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 20% of total femur length from the distal growth plate. Measurement units: mm\^3.

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Stress-Strain Index at the Femur 20% Site
582.69 mm^3
Standard Deviation 202.42
504.12 mm^3
Standard Deviation 202.34

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in total volumetric bone density at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Total Volumetric Bone Density at the Tibia 4% Site
26.76 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 29.35
28.22 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 30.58

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of trabecular bone at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Volumetric Bone Density of Trabecular Bone at the Tibia 4% Site
7.23 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 17.18
7.37 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 13.97

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of cortical bone at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Volumetric Bone Density of Cortical Bone at the Tibia 4% Site
25.94 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 28.46
27.29 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 29.54

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in trabecular bone area at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: square millimeters (mm\^2).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Trabecular Bone Area at the Tibia 4% Site
35.83 millimeters squared (mm^2)
Standard Deviation 75.98
34.81 millimeters squared (mm^2)
Standard Deviation 70.70

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in cortical bone area at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: square millimeters (mm\^2).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Cortical Bone Area at the Tibia 4% Site
66.42 millimeters squared (mm^2)
Standard Deviation 73.94
65.50 millimeters squared (mm^2)
Standard Deviation 69.84

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in periosteal circumference at the tibia 4% site . Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Periosteal Circumference at the Tibia 4% Site
4.65 millimeters (mm)
Standard Deviation 5.15
4.64 millimeters (mm)
Standard Deviation 4.82

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in bone strength index (BSI) at the tibia 4% site. Bone Strength Index (BSI) is a measurement of the resistance to compression forces at the epiphyses of long bones. Measurement made by pQCT at a distance of 4% of total tibia length from the distal growth plate. Measurement units: mm\^4.

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Bone Strength Index at the Tibia 4% Site
16.86 mm^4
Standard Deviation 10.14
17.28 mm^4
Standard Deviation 9.35

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in total volumetric bone density at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Total Volumetric Bone Density at the Tibia 50% Site
39.83 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 32.94
37.26 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 29.74

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of trabecular bone at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Volumetric Bone Density of Trabecular Bone at the Tibia 50% Site
-4.00 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 14.16
-3.51 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 15.84

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of cortical bone at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Volumetric Bone Density of Cortical Bone at the Tibia 50% Site
31.06 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 26.75
33.70 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 27.35

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month measurement of periosteal circumference at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Periosteal Circumference at the Tibia 50% Site
5.27 millimeters (mm)
Standard Deviation 1.63
5.26 millimeters (mm)
Standard Deviation 2.12

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in cortical thickness at the tibia 50% site . Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Cortical Thickness at the Tibia 50% Site
.53 millimeters (mm)
Standard Deviation .28
.51 millimeters (mm)
Standard Deviation .28

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in strength-strain index at the tibia 50% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 50% of total tibia length from the distal growth plate. Measurement units: mm\^3.

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Stress-Strain Index at the Tibia 50% Site
336.49 mm^3
Standard Deviation 112.47
322.78 mm^3
Standard Deviation 114.10

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in total volumetric bone density at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Total Volumetric Bone Density at the Tibia 66% Site
19.26 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 41.46
17.83 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 38.18

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of trabecular bone at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Volumetric Bone Density of Trabecular Bone at the Tibia 66% Site
1.69 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 16.02
4.48 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 14.20

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in volumetric bone density of cortical bone at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: milligrams per cubic centimeter (mg/ccm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Volumetric Bone Density of Cortical Bone at the Tibia 66% Site
31.06 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 28.49
28.96 milligrams per cubic centimeter (mg/ccm)
Standard Deviation 28.71

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in periosteal circumference at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Periosteal Circumference at the Tibia 66% Site
6.82 millimeters (mm)
Standard Deviation 3.06
6.75 millimeters (mm)
Standard Deviation 3.07

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in cortical thickness at the tibia 66% site . Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: millimeters (mm).

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Cortical Thickness at the Tibia 66% Site
.32 millimeters (mm)
Standard Deviation .31
.32 millimeters (mm)
Standard Deviation .27

PRIMARY outcome

Timeframe: Baseline to 24-months

Population: Population consists of all participants that had complete measurements at the baseline, 12-month and 24-month time points (N=207). At 12-months: Age=11.8 +/- 1.0 yrs; Height=153.3 +/- 9.9 cm; Weight=44.0 +/- 9.3 kg. At 24-months: Age=12.8 +/- 1.0 yrs; Height=158.8 +/- 9.1 cm; Weight=50.0 +/- 10.7 kg.

Baseline to 24-month change in strength-strain index at the tibia 66% site. Stress-strain index (also called strength-strain index and stress-strength index in the literature) is a measure of the resistance to torsional and bending forces at diaphyseal sites of long bones. Measurement made by pQCT at a distance of 66% of total tibia length from the distal growth plate. Measurement units: mm\^3.

Outcome measures

Outcome measures
Measure
Control
n=98 Participants
Participants randomized to the control arm did not perform intervention activities. Physical activity was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire (PYPAQ).
Exercise Intervention
n=109 Participants
Participants randomized to the exercise intervention group performed activities designed to provide skeletal loading: impact activities 3 times per week, increasing the number of jumps (up to 40) and increasing height (from 6 inches to 24 inches per repetition) over the initial 8-weeks (2 months). New activities were introduced approximately every 2-3 months in order to continually stress the skeleton over 2 years. Physical activity performed by these subjects (in addition to intervention activities) was objectively assessed by pedometer (7-day wear period) and further assessed by a validated past year physical activity questionnaire PYPAQ).
24-month Change in Stress-Strain Index at the Tibia 66% Site
435.13 mm^3
Standard Deviation 164.78
421.49 mm^3
Standard Deviation 172.67

Adverse Events

Exercise Intervention Arm

Serious events: 0 serious events
Other events: 0 other events
Deaths: 0 deaths

Control Arm

Serious events: 0 serious events
Other events: 0 other events
Deaths: 0 deaths

Serious adverse events

Adverse event data not reported

Other adverse events

Adverse event data not reported

Additional Information

Dr. Scott Going, Ph.D.

University of Arizona

Phone: 520-626-3432

Results disclosure agreements

  • Principal investigator is a sponsor employee
  • Publication restrictions are in place