Associations of ankle strength and range of motion with reactive strength performance in elite youth soccer players

Ankle dorsiflexion and plantar flexion are fundamental movements that contribute to lower-limb stability and explosive performance in sports. Adequate ankle strength and active range of motion (AROM) may be associated with athletic performance, whereas limitations in these parameters may be associated with impaired function and increased injury risk. Therefore, this study aimed to examine the associations between ankle strength, AROM, and reactive strength index (RSI) in youth soccer players. A total of 79 male youth soccer players from the U15, U16, U17, and U19 age categories participated in the study. Isometric ankle strength, ankle ROM, and RSI were assessed, and their associations were examined using forced-entry multiple linear regression models, in which dominant- and non-dominant-leg dorsiflexion and plantar flexion values were entered simultaneously as predictors of RSI outcomes, as predictors of RSI outcomes, with Benjamini–Hochberg false discovery rate (FDR) correction applied to account for multiple comparisons. In the dominant leg (DL), both dorsiflexion and plantar flexion AROM were associated with DL RSI, explaining 18.0% and 15.5% of the variance, respectively. In the non-dominant leg (NDL), plantar flexion AROM showed a significant association with NDL RSI (17.4% of variance), whereas the association with dorsiflexion AROM (5.3%) did not remain significant after correction for multiple comparisons. For two-leg RSI, DL dorsiflexion AROM, DL plantar flexion AROM, and NDL plantar flexion AROM explained 9.6%, 7.4%, and 8.6% of the variance, respectively. Regarding strength variables, DL dorsiflexion and plantar flexion strength explained 8.9% and 12.9% of the variance in DL RSI, whereas NDL dorsiflexion strength explained 23.3% of the variance in NDL RSI. For two-leg RSI, DL dorsiflexion strength, DL plantar flexion strength, and NDL dorsiflexion strength explained 12.3%, 18.2%, and 14.8% of the variance, respectively. Overall, DL plantar flexion strength and NDL dorsiflexion strength showed the strongest associations with RSI outcomes. These findings suggest that ankle ROM and strength may be associated with reactive strength performance in young soccer players, although the explained variance was generally low-to-moderate across models (R² = 5.3–23.3%). In particular, dominant-leg plantar flexion strength and non-dominant-leg dorsiflexion strength appear to be relevant contributors to RSI outcomes. Accordingly, targeted mobility and strength exercises for the ankle joint may help support reactive strength performance.