Biomechanical analysis of the tucked front somersault on vault among elite junior female gymnasts

The tucked front somersault (TFS) is a compulsory maneuver in competitions for junior female gymnasts on vault in China. Analyzing the biomechanics and identifying potential errors in the TFS on vault among elite junior female gymnasts is crucial for optimizing the training of forward salto skills and for facilitating the development of more complex variations. This study utilized the Noraxon MR3 wireless surface electromyography (sEMG) system, Kistler 3D force plates, and an intelligent testing system to analyze the performance of TFS on vault. The participants consisted of 20 elite junior female vaulters. Key variables analyzed included lower limb sEMG signals, run-up velocity, jump ground reaction force (JGRF) during take-off, flight height, flight distance, flight duration, and joint angles at the instances of take-off and landing. (1) Significant bilateral differences were observed in the muscle contribution rates of the gluteus maximus, rectus femoris, hamstrings, tibialis anterior, and gastrocnemius during TFS (p < 0.05) on vault, with the left side generally exhibiting higher contribution rates than the right side. (2) The take-off angle averaged 71.65°. JGRF was significantly correlated with run-up velocity (ρ = 0.546, p < 0.05), as well as with flight height (ρ = 0.816, p < 0.01), flight distance (ρ = 0.576, p < 0.05), and flight time (ρ = 0.718, p < 0.01). (3) During the flight phase, 25% of the athletes initiated body extension before completing 340° of somersault rotation, while 35% initiated extension after exceeding 375° of somersault rotation. (4) In the landing phase, knee and hip joint extension angles were relatively small at foot contact (115.32 ± 4.56° and 121.58 ± 4.37°, respectively). This study offers a phase-specific and mechanistically integrated biomechanical explanation of performance constraints during the TFS vault in junior female gymnasts. Athletes demonstrated bilateral asymmetry in thigh muscle force contribution during the TFS vault. During take-off, JGRF emerged as the primary mechanical determinant of flight height, distance, and duration, yet inadequate lower-limb extension likely constrained its effective generation. During flight, suboptimal timing of full-body extension compromised landing readiness and postural control. During landing, insufficient knee and hip extension reduced the available buffering range and impaired impact dissipation efficiency.