Lower-limb mechanics during the support phase of maximum-velocity sprint running.

INTRODUCTION: The forces produced by an athlete during the support phase of a sprint run are a vital determinant of the outcome of the performance. The purpose of this study was to improve the understanding of sprint technique in well-trained sprinters through the comprehensive analysis of joint kinetics during the support phase of a maximum-velocity sprint.

METHODS: Four well-trained sprinters performed maximum-effort 60-m sprints. Two-dimensional high-speed video (200 Hz) and ground-reaction force (1000 Hz) data were collected at the 45-m mark. Horizontal velocity, step length, step frequency, and normalized moment, power, and work, via inverse dynamics, were calculated for two trials in each athlete.

RESULTS: The hip extensors performed positive work in early stance (normalized value = 0.063 +/- 0.017), and the plantar flexors performed positive work in late stance (normalized value = 0.053 +/- 0.010). The knee extensors played a negligible role in positive work generation throughout stance.

CONCLUSIONS: In contrast to previous findings, the knee moment did not contribute substantially to power generation during the latter part of the support phase. This may be explained in part by the specific technical requirements of the maximum-velocity phase of the sprint. However, major periods of power generation of the hip extensors in early stance and of the plantar flexors in late stance were observed. The action of the knee joint during the support phase may therefore have been more of a facilitator for the radial transfer of power from the hip through the ankle on to the track.