Force-Time Characteristics and Running Velocity of Male Sprinters during the Acceleration Phase of Sprinting

Abstract

In an effort to investigate the force-time characteristics during the acceleration phase of the sprint start, eight male sprinters were used as subjects. Runs up to 3 m were analyzed from film, and force-time parameters were measured on a force platform. In a starting stance the reaction time of the group was .118 ± .016 s and the force production lasted .342 ± .022 s. The maximal resultant force at the moment of maximal horizontal force was 19.3 ± 2.2 N x kg¹, and the direction of the force was 32 ± 7°. In the very last instant before leaving the blocks the velocity of the center of gravity was 3.46 ± .32 m x s⁻¹. In the first contact after leaving the blocks there was a braking phase (.022 ± .005 s in duration) during which the average horizontal force was −153 ± 67 N. The braking phase was observed despite the body center of gravity being horizontally ahead by .13 ± . 05 m with respect to the first contact point. The percentage of deceleration in running velocity during that phase was 4.8 ± 2.9%. In the propulsion phase the average horizontal force was great (526 ± 75 N), and it was produced for a relatively long time (.171 ± .035 s). Significant correlation coefficients were observed between force production and running velocity. These results suggest that braking/propulsion phases occur immediately after the block phase and that muscle strength strongly affects running velocity in the sprint start.

Key Words:

• force-time characteristics
• sprint start
• running
• braking phase