Critical Examination of Ground Reaction Force in the Running Forward Somersault

Abstract

Ground reaction forces (GRF) elicited by nine male gymnasts during a running forward somersault were examined to investigate their characteristics in relation to the performance. Support averaged 135 ms with braking GRF dominating in the antero-posterior direction. Vertically, impact averaging 13.6 body weights (BW) was recorded followed by a second peak of 6.1 BW. The relative minimum in vertical GRF and lowest body position coincided temporally at 23% of support time; maximum knee flexion and minimum distance between the center of gravity (CG) and the support point occurred at 36 and 37%, respectively; and the second vertical GRF peak and maximum dorsiflexion were registered at 44%. The results suggested that, while vertical touchdown and last contact velocities of the CG could be approximated from GRF, eccentric ankle and knee extensor contraction continues beyond the relative minimum in the vertical GRF curve and is more closely related to the period before the CG reaches its minimum distance from the support point.