The goal of this observational study is to to evaluate and correlate muscle activation in the gluteal musculature and ankle stability in a healthy population. The main question it aims to answer is: Is there a significant positive correlation between gluteal muscle activation and ankle stability?

Participants will complete questionnaires on the functionality of foot and ankle pathologies related to their daily life and sports activities, and perform specific physical tests to assess muscle strength, ankle stability, and activation of the lower extremity musculature.

The main outcomes were the muscle activation (gluteus maximus, gluteus medius, tibialis anterior, and peroneus longus) of both limbs during a Single Leg Stance test and a Hurdle Step test (Check Your Motion, Albacete, Spain). Muscle activation was assessed using surface electromyography, and the results will be described as a percentage of Maximum Isometric Voluntary Contraction (%MVIC). Ankle stability was evaluated according to the criteria established by Perrot using a force platform (Dynamic Walkway P6000, BTS Bioengineering, Milan, Italy).

There are no previous studies evaluating a possible correlation between gluteus maximus muscle activity and ankle stabilization capacity. Therefore, a sample size calculation was performed with the aim of detecting a strong correlation as statistically significant (r=0.5) according to the criteria of Hopkins et al [33]. The G*Power 3.1 program was used to calculate the sample size. The statistical test used was "Correlation: Bivariate Normal Model", the type of power analysis was "A priori: compute required sample size - given alpha, power and effect size". An error α=0.05 and a statistical power of 0.80 (β=0.20) was used. The result of the test was 29 subjects required to perform this research.

The study investigators will sign a data confidentiality sheet where they commit to use the data with appropriate confidentiality. In addition, after analyzing the results, the participant's face will be hidden so that he/she cannot be recognized.

The data will be collected on a form designed for this purpose and will be entered into a database created with the Microsoft Office Excel® 2021 program, in a URV system subject to the security measures of the National Security Scheme, always in areas where only the research staff of this project can access. Subsequently, the SPSS program (Statistical Package for the Social Sciences) version 26.0 for Windows® will be used to analyze the data.

The normality of all variables will be examined using the Saphiro Wilk statistical test. Descriptive statistics for all variables will be expressed as mean (standard deviation) if the variable follows a normal distribution and as median (interquartile range) if the variable does not follow a normal distribution. Subsequently, correlation analysis will be performed using Pearson's correlation test (if both variables are normal) or Spearman's Rho (if either variable does not follow a normal distribution). Correlations will be classified as weak (r=0.1), moderate (r=0.3), strong (r=0.5), large (r=0.7) or very large (r=0.9) [33]. Correlations will be described as statistically significant if the p-value is less than 0.05. If the correlation coefficient is statistically significant, the coefficient of determination (R2) will be calculated. Bonferroni correction for multiple comparisons will be applied based on the correlations finally evaluated.

Inclusion Criteria:

• To be between 18 and 35 years of age.
• To sign the informed consent form.
• Failure to meet the exclusion criteria.

Exclusion Criteria:

• To have an injury at the time of selection.
• To have psychological and/or psychiatric illnesses.
• To take anticoagulants, to have an infectious process.
• To have a heart disease.
• To be hypersensitive to pain.
• To have skin infections.

Health students from the Faculty of Medicine and Health Sciences of the Rovira i Virgili University.