Comparison of the effect of acute and delayed fatigue on the time to stability of female gymnasts with and without dynamic knee valgus during drop-landing task

Drop landing is one of the tasks performed in many sports skills. Lower limb injuries have the highest prevalence in sports where jump landing is repeated frequently. One of the most common landing injuries is an anterior cruciate ligament (ACL) tear, which increases knee valgus and may contribute to an increased risk of ACL injury in athletes. In this situation, fatigue is one of the components that can affect various parameters of the landing task. The purpose of this study was to investigate and compare the acute and delayed effects of fatigue on the time to stability (TTS) of female gymnasts with and without dynamic knee valgus (DKV) during the landing task. In this semi-experimental study with a pretest-posttest design, 42 female gymnasts were selected through purposive and available sampling and divided into two groups of 21: a control group without DKV and an experimental group with DKV. The TTS in these individuals was measured before, after, and 24 hours after the fatigue protocol using the Kistler force plate device. The data was analyzed using SPSS software and statistical methods of analysis of covariance with repeated measures at a significance level of P≥0.05. According to the findings of this study, it showed that there is a significant difference in the variable of TTS in three time periods (before, after, 24 hours after fatigue) in the control and experimental groups (P= 0.026). The results of the present study showed that plyometrics on the TTS are significantly different between people with DKV and without DKV, and people with DKV are necessarily at a greater risk of injury during landing tasks.