Abstract
Background:
A back handspring (BHS) is a fundamental gymnastics skill in which the upper extremities (UE) are used as a weight-bearing surface to propel the gymnast flipping backwards and landing in a standing position. Gymnasts experience forces of up to 4 times their body weight while contacting the ground, which may increase the risk of UE injuries.
Hypothesis:
To assess sagittal plane UE joint angles and peak vertical ground reaction forces (vGRF) experienced by young female gymnasts while performing a BHS.
Methods:
A cross-sectional, controlled laboratory study was used. Twenty-three healthy female gymnasts (mean ± SD; age = 12.3±1.5 years; height = 143.4±7.6 cm; body mass 37.7±6.6 kg) performed BHS. UE joint angles were assessed using a 10-camera, marker-based motion analysis system (240fps). Contact vGRF were measured using dual force plates (1200Hz). BHS trials were time-normalized to 101 time-points (0-100%) from the point of initial contact to the point of hand-off and broken down into two sub-phases: Contact Phase 1 (0-49%) and Contact Phase 2 (50%-100%). Descriptive statistics including mean, standard deviation, and 95% confidence interval (95%CI) were used.
Results:
During Contact Phase 1, mean wrist joint extension ranged from 38.5±8.4◦(34.5, 42.6) to 66.3±8.9◦(62, 70.5), mean elbow joint flexion ranged from 16.7±3.5◦(15.2, 18.3) to 46.2±12.8◦(40.7, 51.7), and mean shoulder joint flexion ranged from 132.7 ± 18◦(124.9, 140.5) to 173.2±7.6◦(169.9, 176.4). During Contact Phase 2, mean wrist joint extension ranged from 23.7±10.6◦(18.6, 28.8) to 58.8±7.8◦(55, 62.6), mean elbow joint flexion ranged from 15.1± 5.4◦(12.8, 17.5) to 41.6 ± 13.5◦(35.8, 47.4), and mean shoulder joint flexion ranged from 125.2 ± 14.3◦(11.8, 17.8) to 140 ± 11.9◦(134.9, 145.1). Peak normalized vGRF of 16.1± 2.6 N/kg (14.9, 17.3) were measured during Contact Phase 1 and 5.0 ±1.2 N/kg (4.4, 5.5) during Contact Phase 2.
Conclusion:
In conclusion, this is one of the first papers to investigate the biomechanics of the UE while performing a BHS. Coaches and clinicians should encourage elbow flexion, and increased shoulder forward flexion for injury prevention of the UE while performing a BHS. Clinicians can use this normative biomechanical data when assessing a standing BHS and considering return-to-sport benchmarks in young female gymnasts.