Author(s): TSENG, Y., HUNG, M., CHANG, H., Institution: NATIONAL TAIWAN SPORT UNIVERSITY, Country: TAIWAN, Abstract-ID: 796

INTRODUCTION:
The importance of kinetic chain transmission in the lower extremities has gained widespread attention in recent years. Previous studies have demonstrated that limited ankle dorsiflexion range of motion (DFROM) disrupts kinetic chain efficiency, leading to increased ground reaction force (GRF) characteristics and lower extremity stiffness during the landing phase of a drop jump. Such limitations may result in compensatory movements, such as reduced knee flexion displacement and increased knee valgus during landing, thereby elevating the risk of lower limb injuries, including anterior cruciate ligament (ACL) tears. While extensive evidence supports static stretching as a common and effective intervention for improving ankle DFROM, few studies have quantified the subsequent changes in kinetics, kinematics, and movement sequencing during jump landings. Consequently, it remains unclear whether improving ankle DFROM directly impacts athletic performance. This study aimed to investigate the effects of limited ankle DFROM on 2D kinematics and kinetics during jump landings and to explore the differences in these parameters before and after a stretching intervention.
METHODS:
Nine recreationally active individuals (mean age: 20.22 ± 1.79 years; height:1.69 ± 0.10 m; weight: 65.67 ± 9.95 kg) were recruited. Baseline measurements included ankle DFROM during a weight-bearing lunge test (WBLT) with a flexed knee, as well as kinetic and 2D kinematic data from countermovement jumps (CMJ), drop jumps (DJ), and the Landing Error Scoring System (LESS). Using a threshold of 36.5°, all participants were identified as having limited DFROM (mean: 27.96 ± 4.30°). The intervention consisted of a 5-week static standing straight-knee stretching protocol using a slant board at a 20°-30° incline, performed 3 days per week (5 sets of 30 seconds per session). Post-intervention data were collected following the 5 weeks. Non-parametric Wilcoxon Paired Sample signed-rank tests were used to analyze the differences in DFROM, CMJ, DJ, and LESS parameters before and after the intervention.
RESULTS:
A significant increase in ankle DFROM was observed following the static stretching intervention, with mean values rising from 27.96 ± 4.30° at pre-test to 36.46 ± 1.75° at post-test (p =.008). However, no significant differences were found in the kinetic parameters for CMJ and DJ, nor in the 2D kinematic parameters for the LESS (p >.05).
CONCLUSION:
A 5-week stretching intervention performed three times per week effectively enhances ankle range of motion, confirming that long-term, regular static stretching can mitigate limited ankle mobility. Nevertheless, despite the significant improvement in DFROM within the restricted group, no corresponding changes were observed in CMJ/DJ kinetics or LESS kinematics. This outcome indicates that only increasing ankle dorsiflexion angle may not exert an immediate or significant impact on overall athletic performance or landing mechanics.