Effect Of ACL Injury Risk In Men With Chronic Ankle Instability During Stop-jump And Sidestep Cutting Movement

Objective: to investigate the effect of chronic ankle instability(CAI)on ACL injury risk of men in movements such as stop-jump and sidestep cutting and analyze the biomechanical mechanism of the effect.Methods: 15(male)objectives with ankle instability were selected as the experimental group and 15(male)healthy objectives as the control group.Both groups completed stop-jump and sidestep cutting movements three times.The wireless surface electromyography system was used to collect the lower limb surface electromyography data of the two groups within 50 ms before(pre-activation)and after(post-activation)the landing of the two movements.The peak VGRF,the peak PGRF,the horizontal distance from COP to ankle joint,and the moment of knee joint at the timing of the peak PGRF were collected by the force measuring system.The infrared high-speed motion capture system was used to collect the three-dimensional knee angles of the two groups at the timing of landing and peak PGRF.The biomechanics of the knee joints of the two groups were compared when they perform stop-jump and sidestep cutting and the ACL injury risk of the two groups of subjects was analyzed.Results: During the stop-jump,the knee flexion angle at the timing of landing in the CAI group was higher than that in the control group(P<0.05)and the knee flexion angle at the peak PGRF was higher than that in the control group with significant difference(P<0.01).After landing,the peak PGRF in CAI group was smaller than that in control group(P<0.05),and the knee extension moment at the timing of peak PGRF was also smaller than that in control group(P<0.05).The horizontal distance from COP to ankle in CAI group was smaller than that in control group(P<0.05).In the preactivation phase,the root mean square(RMS)amplitude of gastrocnemius in CAI group was smaller than that in control group.In the post-activation phase,the RMS amplitude of the vastus medialis oblique,the vastus lateralis,the gastrocnemius and the coactivation of quadriceps-to-hamstrings in the CAI group were all lower than those in the control group(P<0.05).There was no significant difference among other indicators(P>0.05).During sidestep cutting,the knee flexion angle at the time of landing and peak PGRF in the CAI group was larger than that in the control group(P<0.05).The peak PGRF and the knee extension moment at peak PGRF were also smaller than the control group(P<0.05).During the pre-activation and post-activation phases,the RMS amplitude the gastrocnemius and the vastus medialis oblique in the CAI group were smaller than those in the control group(P<0.05),and there was no significant difference in other indexes(P>0.05).Conclusion:(1)During the two movements,CAI objectives exhibit a lower risk of ACL injury: larger knee flexion angle after landing,smaller peak PGRF,lower knee extension moment at peak PGRF(2)CAI male objectives may inhibit the performance in two actions due to their self-protection mechanism,thereby reducing the risk of ACL injury.