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

Overview

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.

SCIENTIFIC BACKGROUND Judo is a martial art and Olympic sport practiced by more than 10 million people worldwide and is the sixth most practiced sport in Spain. The objective of judo is to knock down an opponent of the same weight category by causing loss of balance through grappling, displacements, and defensive and/or offensive actions. During fights, judokas make great physical efforts that require significant muscle strength, an optimal range of joint movement, and the ability to maintain different attack and defense postures. Postural control is essential in martial arts because success is mainly based on preserving the center of gravity within the base of support, which continuously changes to obtain a stable position and to be able to execute specific skills and cause the opponent to lose their balance. A judoka's stability is continuously changing during the fight due to quick center of gravity changes, making the judoka combine bipedal with single-leg support to achieve better balance. Studies have shown that specific judo training can affect the generation of strength, morphological structure, and arch function of the foot. However, it is not known whether different foot types (neutral, pronated, and supinated) can condition the stability and performance in judo. Previous evidence indicates that foot type, assessed using the Foot Posture Index (FPI-6), influences dynamic stability in healthy populations. However, studies on judokas are scarce and limited to non-adult categories. Tests such as the Y Balance Test (YBT) have been proposed as valid tools for assessing dynamic balance and the risk of lower limb injury. The YBT is a dynamic test that requires strength, stability, and proprioception. The present study provides new data on the relationship between foot type and dynamic stability in judokas, identifying those morphologies associated with lower stability and higher injury risks. STUDY OBJECTIVES Primary Objective: To analyze the degree of dynamic stability through the Y Balance Test in judokas according to the type of foot they present as determined by the Foot Posture Index (FPI-6). Secondary Objectives: 1. To analyze the relationship between dynamic stability and different sociodemographic variables (age, sex, training frequency, years practicing judo) 2. To relate injury history with stability in lower limbs 3. To determine if there are significant differences in dynamic stability between the habitual supporting foot and non-habitual supporting foot in the development of specific sports techniques METHODOLOGY Study Design: This is a cross-sectional observational study with quantitative methodology carried out on judokas from the Galician provinces of A Coruña and Pontevedra, Spain. The study was approved by the Research Ethics Committee of the Catholic University of Valencia (protocol code UCV/2022-2023/111, approval date: January 26, 2023). Sample Size: A total of 45 participants were selected and divided into 3 groups of 15 based on their Foot Posture Index (FPI-6) scores: pronated foot group, neutral foot group, and supinated foot group. Inclusion Criteria: * Federated judokas between 15 years (first year of cadet category) and 40 years old * Judokas who perform at least 2 training sessions per week * Judokas who have been federated and practicing judo for at least 3 years Exclusion Criteria: * Judokas with any systemic disease that involves morphological or biomechanical alterations * Judokas who present biomechanical limitations of the lower limbs * Participants who refuse to be measured or to have data taken at the time of the procedure DATA COLLECTION PROCEDURES Participants who agreed to participate were assessed in their training centers. First, they completed a form collecting the following data: * Age, sex, weight category, shoe size * Usual single-leg support foot * Years practicing judo * Hours of judo training per week * History of injuries (location, type, and context of injury) ASSESSMENT PROCEDURES Foot Posture Index (FPI-6): The postural index of the foot was determined using the FPI-6, a validated test used in research and clinical practice. Values were obtained through palpation and visual inspection of 6 items: talus head palpation, supra and infra malleolar curve, relaxed position of the calcaneus in support, navicular prominence, congruence of the internal longitudinal arch, and the degree of adduction/abduction of the forefoot with respect to the rearfoot. Each item is assessed on a 5-point scale ranging from -2 to +2, with -2 corresponding to a high supination position, 0 to a neutral position, and +2 to a maximum pronation position. The FPI-6 value is the sum of all values obtained in each item, providing scores between -12 and +12. Feet with a postural index from -12 to -5 were considered highly supinated, -4 to -1 supinated, 0 to +5 neutral, +6 to +9 pronated, and +10 to +12 highly pronated. Y Balance Test (YBT): Dynamic balance was evaluated through the Y Balance Test, a dynamic test that requires strength, stability, and proprioception. Three branches were placed on the tatami with one in the anterior direction, one posteromedial, and one posterolateral, each separated by an angle of 120°. With one foot on the junction of the 3 branches and the other in the air, participants had to push with their toes segments of a judo belt placed on each branch as far as possible. This touch should be soft to prevent the recovery of balance. Once the segment was left at the most distal end, the foot was returned to the center of the "Y" and the process was repeated with the remaining branches. During the test, hands were placed on the waist to maintain balance. Before the test, lower limbs were measured from the anterior-superior iliac spine to the most distal part of the tibial malleolus. Participants were allowed four practice attempts with each leg to familiarize themselves with the test. Then, each participant made 3 valid attempts with each leg, always starting with their usual supporting foot in single-leg techniques. To obtain values, the three distances reached after each attempt were added together and an average was calculated. This average was divided by the length of the supporting leg multiplied by three, then multiplied by 100 to obtain a percentage score. The test was considered invalid and had to be repeated when: (1) the participant was unable to maintain single-leg support, (2) moved the supporting foot, (3) was unable to return to the starting position with the reaching foot, or (4) used the final touch to regain balance. STATISTICAL ANALYSIS Descriptive analysis of all variables was performed. Quantitative variables were described using measures of central tendency (mean and median) and dispersion (standard deviation, minimum, and maximum). Qualitative variables were described as absolute value (n) and percentage. For the main objective, the Shapiro-Wilk test was performed to determine whether variables were normally distributed. One-factor ANOVA was performed to check for significant differences between groups, and the homogeneity of variance test was conducted to verify homoscedasticity. To check differences between means, Dunnett's T3 test was performed. In bivariate analysis, the Kolmogorov-Smirnov test was performed to verify normal distribution of variables. Student's t-test was then conducted to check mean differences between study variables. All tests were conducted with a two-sided approach. Values of p \< 0.05 were considered significant. Statistical analysis was performed using SPSS 22.0 software. SCIENTIFIC RELEVANCE This study addresses an important gap in scientific knowledge about dynamic stability in judokas. The knowledge gained will allow trainers to evaluate their athletes, enabling better sports conditioning, reduction of injuries, and improvement of sports performance. For healthcare professionals, particularly podiatrists and sports medicine specialists, these findings provide valuable information for clinical assessment, injury prevention strategies, and return-to-sport decision-making following lower limb injuries.