Plantarflexion and frontal-plane strength predict dynamic balance in youth athletes: a cross-sectional study

Ankle strength is essential for dynamic stability and athletic performance. However, its specific relationship with commonly used functional tests remains underexplored in youth athletes. Understanding these associations may inform more targeted training approaches and injury prevention strategies. This study aimed to investigate whether isokinetic ankle strength predicts performance in three widely used functional tests, the Modified Star Excursion Balance Test, the Side Hop Test, and the Weight-Bearing Lunge Test, in youth male soccer players. Twenty-six male soccer players (mean age: 18.5 ± 0.6 years) underwent isokinetic strength assessments, including plantarflexion, dorsiflexion, inversion, and eversion, and performed the Modified Star Excursion Balance Test, the Side Hop Test, and the Weight-Bearing Lunge Test. Limb symmetry was confirmed through paired t-tests, allowing the use of bilateral averages. Pearson correlation coefficients and Least Absolute Shrinkage and Selection Operator regression models were applied to examine associations and predictive capacity. Significant correlations were found between plantarflexion, inversion, and eversion torque and performance in the Modified Star Excursion Balance Test (correlation coefficients ranging from 0.70 to 0.81), particularly in the posteromedial and posterolateral directions. Performance in the Weight-Bearing Lunge Test was positively associated with plantarflexor torque (correlation coefficient = 0.54), while dorsiflexor strength showed no significant relationship. None of the isokinetic strength variables predicted the time in the Side Hop Test. Regression models using the Least Absolute Shrinkage and Selection Operator confirmed plantarflexion and frontal-plane torques as consistent predictors of performance in the Modified Star Excursion Balance Test and the Weight-Bearing Lunge Test. Ankle strength, particularly in plantarflexion and frontal-plane movements, plays a key role in dynamic balance and mobility but appears to be less influential in agility-focused tasks such as the Side Hop Test. These findings support the incorporation of strength training targeting multiplanar ankle control and highlight the importance of neuromotor training to enhance agility in youth athletes.