Positioning the legs in performing spike technique significantly contributes to the development and prevention of lower limb injuries. The present study aimed to evaluate and compare the feedback and feedforward activaties of selected lower limb muscles during triple jump spike with and without toe-in landing in female volleyball players. Methods:In this controlled-laboratory study, 15 female elite volleyball players performed triple spike in toe-in and neutral positions. The electrical activity of tibialis anterior, proneus longus, gastrocenemius, vastus medialis, vastus lateralis, semitendinosus, and biceps femoris muscles was recorded using a 16-channel surface electromyography device (Baya Med Company). The Dependent Samples t-test was applied to analyze the obtained data at the 95% confidence level.Results: In toe-in landing, the semitendinosus muscle activity (P=0.040) significantly decreased in the feedforward phase. Besides, in the feedback phase, there were significant increases in tibialis anterior (P=0.039) and proneus longus (P=0.043). Eventually, a significant decrease was observed in the medial gastrocenemius (P=0.042) and biceps femoris muscle (P=0.047) activities. Conclusion:Decreased biceps femoris muscle activity during the feedback phase with the toe-in position may be associated with the decreased supportive effect of hamstring muscle, increased anterior knee shear force, and subsequently anterior cruciate ligament injury. Increased activity of leg and ankle muscles may also increase the odds of muscular fatigue and subsequent ankle sprain during toe-in landing.

Background:Performing exercises or playing sports with an incorrect technique can cause musculoskeletal injuries. Objectives: The present study was conducted to compare the hamstring to quadriceps activation ratio when landing in a two-way spike in female volleyball players. Methods: In this cross-sectional study, 15 elite female volleyball players performed triple jump spikes (TJS) with their toe in and in a neutral ankle position. Electromyography (EMG) was used to measure the muscle activity of the biceps femoris, semitendinosus, vastus medialis and vastus lateralis in two phases before and after the initial contact. Data were analyzed using the Wilcoxon test at the significance level of P < 0.05. Results: The ratio of biceps femoris activity to vastus medialis (P = 0.04) and vastus lateralis (P = 0.04) activities in TJS with a toe-in ankle decreased significantly in the feed-back phase and the ratio of semitendinosus activity to vastus lateralis activity also decreased significantly in the feed-forward phase of TJS with a natural ankle angle (P = 0.02). Conclusions:A lower muscle activity ratio for biceps femoris to vastus lateralis and medialis in the toe-in position may lower hamstring muscle support from the anterior cruciate ligament (ACL) after landing, which might increase the risk of ACL injury when landing.