Analysing The Impact of Foot Arch Height on Leg Muscle Tone and Balance in Young Adults.

Summary

The goal of this observational study is to explore how the shape of the foot arch affects muscle tone, strength, and balance in healthy young adults aged 18-25, of all genders.

The main questions it aims to answer are:

1. Does foot postures as Pes Planus, Pes Cavus, and Normal arch has significant effect on static and dynamic balance performance, lower limb muscle tone, or muscle strength in young adults?
2. What is the functional impact of foot posture on stability, movement efficiency, and injury risk?

Participants will be grouped based on foot arch type: flat (pes planus), high (pes cavus), or normal using Arch Height Index (AHI).

The investigators will compare groups to see if differences in foot arch affect postural stability, muscle tone, and strength. Participants will:

* Complete a sociodemographic questionnaire (Age, gender, physical activity level, dominant leg, and footwear habits), and anthropometric measurements (Height, weight, and BMI).
* Undergo static balance test for both legs:

Single Leg Stance, counting the errors made in 30 seconds for 3 trials.

\- Undergo dynamic balance tests for both legs: Star Excursion Balance Test (SEBT) by reaching in 8 directions while balancing on one foot, and Single-Leg Hop for Distance by hopping forward on one leg.

* Have muscle tone and stiffness assessed using the MyotonPRO device on specified lower limb muscles.
* Have muscle strength measured using a handheld dynamometer (MicroFET2) across major specified leg muscles.

People have different types of foot arches. Some have flat feet (pes planus), some have high arches (pes cavus), and others have normal arches. These variations affect how the body aligns during movement and balance. Flat feet may cause inward rolling (overpronation), fatigue, and pain. High arches may cause stiffness, poor shock absorption, and a higher risk of ankle injuries.

Both arch types can reduce postural control and increase the risk of imbalance. Since lower body muscles are critical for maintaining posture, weak or poorly coordinated muscles can worsen these effects. However, no previous study has comprehensively explored the combination of foot arch structure, muscle tone, muscle strength, and both static and dynamic balance. This study aims to fill that gap.

The results may help healthcare professionals develop better screening and treatment strategies, such as exercise programs, rehabilitation approaches, and shoe recommendations for individuals with flat or high arches. By understanding these factors, the investigators can improve movement efficiency, prevent injuries, and support better quality of life.

All participants will be informed of the study procedures and will provide both written and verbal consent. The study will be conducted in compliance with ethical standards.

Conditions

• Pes Cavus
• Pes Planus
• Muscle Tone
• Balance Assessment
• Muscle Strength
• Static Balance
• Dynamic Balance

Interventions

DIAGNOSTIC_TEST

Arch Height Index

The goal of this assessment is to objectively classify foot posture as low-arched, high-arched, or normal using the Arch Height Index (AHI). Participants will sit with hips and knees at 90°, feet lightly weight-bearing (\~10%), and measurements will be taken with a caliper and paper. AHI is calculated as arch height at 50% of total foot length divided by truncated foot length. Feet with a ratio ≥ 0.356 are classified as high-arched, ≤ 0.275 as low-arched, and 0.276-0.355 as normal. Both feet will be assessed, focusing on the medial longitudinal arch. AHI demonstrates excellent inter-rater and test-retest reliability (ICC = 0.98-1.00).

DIAGNOSTIC_TEST

Foot Posture Index

The participant will be asked to stand still with arms along the side, looking forward and their feet will be assessed according to the index components while being observed by the physiotherapist. Scores between 0 and+5 indicate normal feet; +6 to+9 indicate pronated feet; ≥ +10 indicate highly pronated feet;-1 to-4 indicate supinated feet;-5 to-12 indicate highly supinated feet. The goal of this assessment is to help classifying the participants' foot arch. High inter-rater and test-retest reliability for FPI scoring (ICC values of 0.923 and 0.931).

DIAGNOSTIC_TEST

Single Leg Stance

Static balance will be assessed using the Single Leg Stance (SLS) test. Participants will stand barefoot on one leg with arms along the sides and the non-stance foot lifted clear of the ground. Timing begins when the foot is lifted and ends when balance is lost, defined as placement of the lifted foot, movement of the stance foot, or grasping for support. Each leg will be assessed for a maximum of 30 seconds over three trials, and the mean value will be used for analysis. Longer durations indicate better static postural control. The test will be performed under eyes-open conditions. The SLS test has demonstrated good to excellent test-retest reliability in healthy adults, with ICC values ranging from 0.79 to 0.95, and has shown acceptable reliability and predictive validity for balance assessment in clinical settings.

DIAGNOSTIC_TEST

Star Excrusion Blance Test (SEBT)

Participants will perform the Star Excursion Balance Test (SEBT) barefoot, standing on one leg at the center of a star-shaped layout with 8 directions: ANT, AM, M, PM, P, PL, L, and AL, each at 45° angles. With hands on hips to reduce arm compensation, they will reach in each direction using the opposite leg without shifting weight or losing balance. Reach distance will be marked and trials repeated if form is compromised. Three trials per leg will be completed with 2-minute rests to reduce fatigue. Reach distances will be normalized to leg length (ASIS to medial or lateral malleolus) to ensure fair comparison. The SEBT assesses dynamic balance and has shown good reliability (ICC = 0.75-0.9).

DIAGNOSTIC_TEST

Single-Leg Hop for Distance

The participant will be asked to assume a single-leg stance behind a marked starting line and will be instructed to hop forward as far as possible using a single explosive movement. They must land on the same leg while maintaining stability for at least 2-3 seconds. If the participant loses balance, touches the ground with the other foot, or falls forward, the attempt is not counted. Each participant will perform 3 trials per leg, with a rest period of 30-60 seconds between trials. The longest valid hop distance is recorded for each leg to calculate Leg Symmetry Index. The goal of single-leg hop for distance is to assess the dynamic balance, and it has excellent ICC values for test-retest reliability exceeded 0.86.

DIAGNOSTIC_TEST

Myometer Device

Muscle tone, stiffness, and elasticity will be measured using the MyotonPRO device, a non-invasive tool for evaluating muscle biomechanical properties. Participants will assume standardized positions, and measurements will be taken from the broadest cross-sectional area of the following muscles: M. Peroneus Longus, M. Tibialis Anterior, M. Gastrocnemius, Quadriceps (Vastus Medialis, Rectus Femoris, Vastus Lateralis), and Hamstrings (Biceps Femoris, Semitendinosus). The probe will be placed perpendicular to the skin. Five parameters will be recorded: frequency, stiffness, decrement, mechanical stress relaxation time, and creep. The method demonstrates high intra-rater (ICC = 0.63-0.99) and inter-rater (ICC = 0.63-0.97) reliability for lower limb muscles.

DIAGNOSTIC_TEST

Dynamometer

Muscle strength will be assessed using a handheld dynamometer (HOGGAN MICROFET2), following the manual muscle testing protocols outlined by Kendall. Target muscles include: M. Peroneus Longus, M. Tibialis Anterior, M. Gastrocnemius, Quadriceps, Hamstrings, M. Extensor Hallucis Longus, and Toe Flexors (M. Flexor Hallucis Brevis and M. Flexor Digitorum Brevis). Participants will perform isolated muscle actions against the device at standardized joint angles. Each test will be repeated for 3 trials, with average values recorded. This method effectively detects muscle imbalances and strength changes, and shows high reliability (ICCs often \> 0.9), strong validity versus isokinetic dynamometers, and an MCIT of \~0.58-17.2 N.

OTHER

Height

Standing height was measured using a flexible metal measure to the nearest 0.1 cm

OTHER

Weight

Body weight was measured using a calibrated digital scale to the nearest 0.1 kg.

OTHER

Body Mass Index

Body mass index (BMI) was calculated as weight (kg) divided by height squared (m²) .

Sponsors & Collaborators

• Istinye University

  lead OTHER

Principal Investigators

• Prof. Dr. Habibe Serap İNAL, Doctor of Physical Therapy · Istinye University, Faculty of Health Sciences, Department of Physiotherapy and Rehabilitation

Eligibility

Min Age

18 Years

Max Age

25 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2025-07-02

Primary Completion

2026-04-20

Completion

2026-04-29

Countries

• Turkey (Türkiye)

Study Locations