Determination of the Degree of Dynamic Stability of the Foot in Single-leg Support in Relation to the Foot Posture Index in Judokas

The goal of this observational study is to examine the relationship between foot type and dynamic stability (balance while standing on one leg) in judo athletes. Judo requires excellent balance to perform techniques effectively and avoid injuries. However, there is limited scientific knowledge about how foot posture affects balance in judokas.

The main questions this study aims to answer are:

• Does foot type (neutral, pronated, or supinated) affect dynamic stability in judokas?
• Are there differences in balance between male and female judokas?
• Does injury history affect dynamic stability?
• Is there a difference in balance between the dominant and non-dominant foot?

Participants in this study will:

• Have their foot type assessed using the Foot Posture Index (FPI-6), a clinical tool that evaluates foot alignment
• Perform the Y Balance Test, which measures how far they can reach in three directions while standing on one leg
• Complete a questionnaire about their training history, injuries, and demographic information

All assessments will be conducted in the participants' judo training facilities (tatami) during a single session.

Researchers will compare three groups of judokas (those with neutral, pronated, and supinated feet) to see if foot type influences balance performance. This information may help coaches and healthcare professionals better assess athletes, prevent injuries, and improve sports performance in judo.

Study Overview

• Status: Completed
• Conditions: Athletic Performance; Postural Balance; Sports Injuries; Foot Posture
• Intervention / Treatment: Other: Postural and Balance Assessment

Detailed Description

Judo is a combat sport that places high demands on dynamic postural control due to continuous changes in stance, center of mass, and base of support during throws, defenses, and transitions between standing and ground fighting. Alterations in foot posture (neutral, pronated, or supinated) may modify lower limb biomechanics and could influence dynamic stability and injury risk, but this relationship has not been specifically examined in adult judokas.

This cross-sectional observational study was conducted in federated judokas from clubs in the Galician provinces of A Coruña and Pontevedra (Spain). A total of 45 athletes were classified into three groups according to the Foot Posture Index (FPI-6): pronated, neutral, and supinated feet. Dynamic postural stability was assessed using the Y Balance Test (YBT), normalized to limb length to obtain a composite percentage score for each lower limb. Additional variables included age, sex, training exposure, years practicing judo, dominant (habitual support) foot, and history of neck, spine, hip, or lower limb injuries.

The primary objective is to determine whether dynamic stability differs between foot posture groups. Secondary objectives are to: (1) explore associations between stability and sociodemographic/training variables, (2) examine differences in YBT scores between judokas with and without a history of lower limb or spine injuries, and (3) compare stability between the dominant and non-dominant foot in single-leg techniques. Statistical analyses include descriptive statistics, normality testing, one-way ANOVA with appropriate post-hoc tests for group comparisons, and Student's t-tests for bivariate analyses, with a two-sided significance level of p < 0.05.

The findings are expected to clarify whether specific foot morphologies are associated with reduced dynamic stability in judokas, providing clinically useful information for biomechanical assessment, targeted injury prevention, and performance optimization in this population.

• Study Type: Observational
• Enrollment (Actual): 45

Contacts and Locations

Study Locations

• Spain
  • Valencia
    • Valencia, Valencia, Spain, 46001
      • Catholic University of Valencia San Vicente Mártir

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

Federated judo athletes aged 15 to 40 years from judo clubs in the Galician provinces of A Coruña and Pontevedra (Spain), with at least 3 years of practice and regular weekly training.

Description

Inclusion Criteria:

• Federated judo athletes between 15 and 40 years of age.
• Minimum of 3 years practicing judo.
• At least 2 judo training sessions per week.
• Ability to understand and follow study instructions.
• Signed informed consent (and parental consent for minors, if applicable).

Exclusion Criteria:

• Presence of any systemic disease that may cause morphological or biomechanical alterations of the lower limbs.
• Current biomechanical limitations of the lower limbs that prevent safe performance of the Y Balance Test.
• History of recent lower limb surgery or spinal surgery that may interfere with balance assessment.
• Refusal to undergo measurements or to have data collected at the time of evaluation.

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Judo Athletes; Federated judo athletes aged 15 to 40 years from clubs in A Coruña and Pontevedra, Spain. All participants undergo assessment of foot posture using the Foot Posture Index (FPI-6) and dynamic postural stability using the Y Balance Test in a single evaluation session.	Other: Postural and Balance Assessment; Non-invasive assessment of foot posture using the Foot Posture Index (FPI-6) and dynamic balance using the Y Balance Test performed once in each participant.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Dynamic postural stability score (Y Balance Test) normalized by limb length	Dynamic postural stability will be assessed using the Y Balance Test (YBT). Participants stand on one leg at the center of a Y-shaped grid and reach in three directions (anterior, posteromedial, and posterolateral) with the contralateral leg. Three valid trials will be recorded for each leg after familiarization. For each direction, the mean of the three reach distances (in centimeters) will be calculated and then normalized to limb length (distance from anterior superior iliac spine to distal tibial malleolus) to obtain a percentage score. A composite YBT score will be derived by summing the three normalized reach distances and dividing by three. Higher scores indicate better dynamic postural stability.	Single assessment at baseline (one testing session)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Association between dynamic stability and history of lower limb or spine injuries	Participants will report their history of injuries to the neck, spine, hip, or lower limb using a standardized questionnaire. The normalized composite Y Balance Test score will be compared between judokas with and without a history of such injuries to evaluate whether previous injury is associated with differences in dynamic postural stability.	Single assessment at baseline
Difference in dynamic stability between foot posture groups (pronated, neutral, supinated)	Participants will be classified into three groups according to their Foot Posture Index (FPI-6) scores: pronated, neutral, and supinated feet. The primary Y Balance Test (YBT) composite score, expressed as a percentage, will be compared between these three foot posture groups to determine whether foot type is associated with differences in dynamic postural stability. The YBT composite score is a percentage scale (theoretical range from 0 to values >100), where higher scores indicate better dynamic postural stability.	Single assessment at baseline

Collaborators and Investigators

• Sponsor: Fundación Universidad Católica de Valencia San Vicente Mártir
• Investigators: Principal Investigator: Luis Baraja Vegas, PhD, Catholic University of Valencia San Vicente Mártir

Publications and helpful links

General Publications

• Parada-Souto JC, Part-Ferrer R, Jaenada-Carrilero E, Sales Castellanos C, Gallego-Estévez R. Determination of the degree of dynamic stability of the foot in single-leg support in relation to the Foot Posture Index in judokas. Manuscript submitted for publication.

Study record dates

Study Major Dates

• Study Start (Actual): March 1, 2023
• Primary Completion (Actual): May 23, 2023
• Study Completion (Actual): June 26, 2023

Study Registration Dates

• First Submitted: February 11, 2026
• First Submitted That Met QC Criteria: February 11, 2026
• First Posted (Actual): February 18, 2026

Study Record Updates

• Last Update Posted (Actual): February 20, 2026
• Last Update Submitted That Met QC Criteria: February 18, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Postural Balance; Martial Arts; Athletic Performance; Judo; Y Balance Test; Dynamic Stability; Foot Posture Index (FPI-6); Lower Limb Biomechanics; Single-Leg Support; Sports Injury Risk
• Additional Relevant MeSH Terms: Wounds and Injuries; Athletic Injuries
• Other Study ID Numbers: UCV/2022-2023/111

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No