The Effect of Limited Ankle Dorsiflexion During Emergency Stop—Jump Movements on Lower Limb Biomechanics

Objective The stop‐jump task is a key movement in sports such as basketball and volleyball, with landing biomechanics closely linked to injury risk. Restricted ankle dorsiflexion (DF) alters lower‐extremity mechanics and increases the risk of lower‐limb joint injuries; however, its effects on the full stop‐jump cycle remain unclear. This study examined how restricted DF influences lower‐extremity biomechanics during the stop‐jump task and explored the mechanisms underlying a stiff landing strategy and its potential injury risks. Methods Participants underwent static ankle dorsiflexion range of motion (DF ROM) testing and functional squat assessment. Eligible participants completed walking and stop‐jump tasks, with biomechanical data collected synchronously using motion capture and force plates. Based on peak ankle dorsiflexion angle during walking, 44 participants were categorized into restricted (RADF, n = 22) and unrestricted (unRADF, n = 22) groups. Group differences in lower‐extremity biomechanics across stop‐jump phases were analyzed using ANCOVA with sex as a covariate, with post hoc power reported. Results The RADF group demonstrated significantly greater peak vertical ground reaction force (GRF) and posterior loading rates (LRs) compared with the unRADF group ( p < 0.05). During the horizontal landing phase, ankle plantarflexion and internal rotation angles were significantly increased in the RADF group ( p < 0.05). At the moment of peak GRF during the vertical landing phase, the RADF group exhibited significantly reduced ankle dorsiflexion angle ( p < 0.001) and significantly greater knee abduction angle ( p < 0.05). Additionally, leg stiffness was significantly higher in the RADF group during this phase ( p < 0.05). Conclusion Individuals with restricted DF adopt a stiff landing strategy during stop‐jump, with increased impact loads and abnormal joint kinetics that may impair shock absorption and elevate lower‐extremity injury risk.