Work Rate Adjustments During a High-intensity Interval Training on a Stationary Bike in a Hot and Temperate Environment

Summary

The goal of this repeated measures study is to evaluate acute work rate adjustments during high-intensity interval training (HIIT) in a hot and temperate environment in healthy and active adults when using target heart rate to prescribe the exercise intensity.

The main questions it aims to answer are:

* Will HIIT based on target heart rate in a hot environment result in increased cardiovascular (i.e., elevated recovery HR) and thermal strain compared to HIIT in a temperate environment?
* Will work rate be lowered to a greater extent during HIIT in a hot environment compared to a temperate environment in order to maintain target heart rate?
* Will maximal aerobic capacity (V̇O2max) decrease to a greater extent after HIIT in the heat compared to a temperate environment?

Procedures:

Participants will complete 5 trials on a cycle ergometer. Trial 1 (Control Visit): Participants (n = 7) will have their maximal heart rate and V̇O2max measured in a temperate environment (\~22 °C, 40% RH).

Experimental Trials 2-5: The order of the trials will be counterbalanced and randomly assigned to participants.

* 15TEMP: Participants will cycle at 70% of their maximum heart rate for 8 minutes as a warm-up, followed by one round of HIIT. The HIIT protocol consists of 4 minutes at 90% of maximum heart rate followed by 3 minutes at 70% of maximum heart rate, totaling 15 minutes, in a temperate environment (\~22 °C, 40% RH). After the HIIT session, a graded exercise test will measure V̇O2max.
* 15HEAT: Similar to 15TEMP, but participants will perform the HIIT protocol in a hot environment (\~35 °C, 40% RH).
* 43TEMP: Participants will cycle at 70% of their maximum heart rate for 8 minutes as a warm-up, followed by the HIIT protocol repeated four times (4 minutes at 90% of maximum heart rate and 3 minutes at 70% of maximum heart rate), totaling 43 minutes, in a temperate environment (\~22 °C, 40% RH).
* 43HEAT: Similar to 43TEMP, but participants will perform the HIIT protocol in a hot environment (\~35 °C, 40% RH).

Conditions

• High-Intensity Interval Training
• Heat

Interventions

BEHAVIORAL

15 minutes of high-intensity interval training

Participants completed an 8 min warm-up and 1 round of high-intensity interval training

BEHAVIORAL

43 minutes of high-intensity interval training

Participants completed an 8 min warm-up and 5 rounds of high-intensity interval training

OTHER

Hot environment

Participants exercised in a hot environment, \~ 35 °C, \~40% relative humidity.

OTHER

Temperate environment

Participants exercised in a temperate environment, \~ 22 °C, \~40% relative humidity.

Sponsors & Collaborators

• University of Alabama, Tuscaloosa

  lead OTHER

Study Design

Allocation

RANDOMIZED

Purpose

OTHER

Masking

NONE

Model

CROSSOVER

Eligibility

Min Age

18 Years

Max Age

39 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2021-05-12

Primary Completion

2021-11-14

Completion

2021-11-14

Countries

• United States

Study Locations