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

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.

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.

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).

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.