Musculoskeletal Work in the Longswing on High Bar

Abstract

The aims of this study were to determine the contributions of the gymnast’s musculoskeletal system during the execution of a general longswing on high bar and to evaluate the overall interaction between the gymnast and the elastic bar. Images of four international gymnasts were recorded (50Hz) performing three series of four longswings on a strain gauged high bar (l000Hz). Real world coordinates were reconstructed using 2D DLT and synchronized with the force data. Inverse dynamic analyses were employed to determine joint kinetics during each longswing. Analyses were performed on the whole longswing and on the hip and shoulder ‘functional phases’ defined as maximum extension to flexion at the hips and maximum flexion to extension at the shoulders respectively. The muscle moments and powers at the shoulders were consistently found to be dominant, with maximum values at the shoulders being 4.5 ± 1.70 Nm·kg−1 & 14.4 ± 6.7 W·kg−1 and 2.3 ± 0.5 Nm·kg−1 & 6.0 ± 1.7 W·kg−1 for the hips. In all cases the peak values within the muscle moment profiles occurred within the functional phases highlighting the importance of these active phases to the overall skill. The corresponding muscular work profiles highlighted that an average of 71% ± 6% of the total work occurred during the functional phases of the longswing. Quantification of bar strain energy, based on bar deformation, enabled an energy deficit to be determined. This deficit arose from frictional losses at the hand bar interface, air resistance and bar hysteresis and hence defined the minimum work that the gymnast needed to contribute to complete the circle successfully. These analyses highlighted the dominance of the contribution made by the gymnast between 200° and 240° of rotation, during a successful longswing.