Title

Stepping Back to Improve Sprint Performance: A Kinetic Analysis of the First Step Forwards

Document Type

Journal Article

Publisher

Lippincott Williams and Wilkins

Faculty

Faculty of Computing, Health and Science

School

School of Exercise and Health Sciences

RAS ID

13204

Comments

This is a non-final version of an article published in final form as: Frost, D. , & Cronin, J. B. (2011). Stepping back to improve sprint performance: a kinetic analysis of the first step forwards . Journal of Strength and Conditioning Research, 25(10), 2721-2728. Original article available here

Abstract

Frost DM and Cronin, JB. Stepping back to improve sprint performance: A kinetic analysis of the first step forwards. J Strength Cond Res 25(10): 2721–2728, 2011—Using a step backward to initiate forward movement can increase force and power at push-off and improve sprint performance over short distances. However, it is not clear whether the benefit provided by this paradoxical step influences the mechanics of the first step forwards. Twenty-seven men of an athletic background performed maximal effort 5-m sprints from a standing start and employed a step forwards (parallel and split stance) or backwards (false) to initiate movement. Each sprint was started with an audio cue that also activated the timing gates. Three trials of each starting style were performed and movement (0 m), 2.5-, and 5-m times were recorded. An in-ground force plate placed at the 0-m mark measured the kinetic and temporal characteristics of the first step. Sprint times to 2.5 and 5 m were slower (p < 0.05) when a parallel start was used. No differences were seen in the normalized peak forces (vertical and horizontal) or the vertical impulse between starts, but the vertical mean force was 11 and 12% higher for the false and split starts, respectively. Surprisingly, the parallel start's impulse was significantly greater than that of the false (24%) and split (22%) styles, a consequence of the additional time spent in contact with the ground. The ground contact time, time to peak force, and time from peak force to toe-off (vertical and horizontal) were significantly longer for the parallel start. These temporal variables were also better correlated with sprint performance than any kinetic measure (0.42 ≤ r ≤ 0.75). The false start appears to be advantageous over short distances by improving push-off and the temporal characteristics of the first step.