Background: Surfing requires coordinated lower-limb control to maintain postural stability on an unstable surface and imposes considerable mechanical demands on the ankle joint. Because ankle dorsiflexion contributes to forward tibial progression during dynamic balance tasks, we hypothesized that greater dorsiflexion would be associated with better modified Star Excursion Balance Test (mSEBT) performance, particularly in the anterior direction. Aim: To investigate the association between ankle dorsiflexion and mSEBT performance in youth surfers. Methods: A cross-sectional observational study was conducted between 2024 and 2025 and approved by the Research Ethics Committee of the Universidade do Estado de Santa Catarina (CAAE:86750325.7.0000.0118), in accordance with the Declaration of Helsinki. Twenty-six youth surfers (14 females, 12 males; 16.6±1.1 years) were evaluated. After standardized warm-up, active ankle dorsiflexion was assessed bilaterally in a weight-bearing lunge position using the Measure app on an iPhone as a digital inclinometer. Three trials were performed per limb by the same researcher, and the mean was used. mSEBT reach distances were assessed in the anterior, posteromedial, and posterolateral directions and normalized to limb length; a composite score was calculated. Normality was verified using Shapiro-Wilk test. After confirming normal distribution, right-left comparisons were performed using paired t-tests. As no side-to-side differences were observed, bilateral mean values were used for the planned correlation analysis; front/rear-foot-specific analyses were not performed owing to sample size and study scope. Pearson correlations examined associations between dorsiflexion and mSEBT scores. Results: No significant right-left differences were found for ankle dorsiflexion or mSEBT scores (p>0.05). Dorsiflexion correlated positively with anterior reach (r=0.690,p<0.001), posteromedial reach (r=0.417,p=0.034), and composite score (r=0.429,p=0.029), but not posterolateral reach (r=0.292,p=0.148). Conclusions: Greater ankle dorsiflexion was associated with better mSEBT performance in youth surfers, especially anterior reach. These findings support including dorsiflexion assessment in functional screening, although future studies should examine stance-specific front- and rear-foot demands.
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