Effects of The Lower Limb Muscle Activity During Uphill Sprint Training

Abstract

The purpose of this study was to clarify effect of uphill sprinting to running spatiotemporal variables and lower limb muscle activity. Twelve university sprinters (seven males) were volunteered to this study. Subjects performed 60 m sprint with maximal effort in two conditions (level sprint vs uphill sprint). Then, we obtained running spatiotemporal variables and electromyography (EMG) from lower limb muscles (biceps femoris, rectus femoris, tibial anterior, lateral head of gastrocnemius). We calculated the running spatiotemporal variables (e.g., running speed, step frequency, step length), EMG activity amplitudes (%MVC), and relative EMG timings in running cycle (%) in analysis section (40-60m). We observed running speed, step frequency, and step length were significantly decreased in the uphill sprint. However, no significant differences were observed in EMG activity amplitudes between two conditions. On the other hand, the onset and offset timings of rectus femoris muscle were significantly shifted to the latter half of the running cycle in the uphill sprint. Therefore, we may consider the possibility that delay in the timing of the recovery movement (i.e., hip flexion) of the swing leg in the uphill sprint. These results suggest that uphill sprint training may affect the timing of muscle activity rather than the amount of muscle activity. We conclude that neuromuscular control of the lower limb muscle is different between uphill sprint and level sprint.