How take-off technique affects muscle demand in the back handspring step out in female gymnasts.

When performing the back handspring step out (BHS) on the balance beam, most gymnasts use one of three take-off techniques: Simultaneous Flexion, Sequential Flexion or Double-Bounce. However, it remains unclear which technique results in the lowest muscle demand that could help reduce energy expenditure and fatigue and improve overall performance. The purpose of this study was to use musculoskeletal modelling and simulation to quantify the influence of take-off technique on muscle demand (integrated muscle power) and contributions to the critical biomechanical functions of whole-body angular momentum generation and control and trunk propulsion (mechanical power delivered to the trunk). Simulations of female gymnasts (n = 21; age: 15.3 ± 3.6) were generated using their self-selected BHS technique on a balance beam. Differences in muscle demand were small across the techniques. However, the vasti, ankle plantarflexors, gluteus maximus and hamstring muscle groups experienced large demand during the BHS take-off. The gluteus medius and ankle plantarflexors were crucial for maintaining balance. The hamstrings, ankle plantarflexors and vasti generated needed momentum and delivered power to the trunk. These results provide targets for muscle strengthening and conditioning to improve balance control and increase the height and distance of the BHS, which is needed before adding additional skills in combination.