The importance of ground reaction force (GRF) and the speed with which force is applied during the pushing action away from the ground cannot be overemphasized.These two factors are major determinants of sprint performance for athletes in all sports during each phase of a short sprint.
A study by Nagahara and associates (2017) aimed to investigate the step-to-step spatiotemporal variables and ground reaction forces during the acceleration phase for characterizing intra-individual fastest sprinting within a single session. Step-to-step spatiotemporal variables and ground reaction forces produced by 15 male athletes were measured over a 50-m distance during repeated (three to five) 60-m sprints using a long force platform system. Differences in measured variables between the fastest and slowest trials were examined at each step until the 22nd step using a magnitude-based inferences approach. There were possibly–most likely higher running speed and step frequency (2nd to 22nd steps) and shorter support time (all steps) in the fastest trial than in the slowest trial. Moreover, for the fastest trial there were likely–very likely greater mean propulsive force during the initial four steps and possibly–very likely larger mean net anterior–posterior force until the 17th step. The current results demonstrate that better sprinting performance within a single session is probably achieved by 1) a high step frequency (except the initial step) with short support time at all steps, 2) exerting a greater mean propulsive force during initial acceleration, and 3) producing a greater mean net anterior–posterior force during initial and middle acceleration.
Coaching Application: The more force athletes can apply to the ground, and the faster this force is applied (ground contact time), the greater the start and acceleration speed. Training to increase GRF during early and late acceleration focuses on improving absolute strength (maximum) and speed-strength (applying force quickly each step). Improvement in these areas requires unique training approaches and exercises. *NASE members are referred to the following issues of Sports Speed Digest on the NASE website for specific training exercises and programs:
January: 2015, 2016, 2018, March: 2014, May: 2016, July: 2008, September: 2011, 2014, November: 2013.
Nagahara, Ryu, Mizutani, Akifumi, Matsuo, Hiroaki, Tetsuo Fukunaga. 2017. Step-to-step spatiotemporal variables and ground reaction forces of intra-individual fastest sprinting in a single session. Journal of Sports Sciences. Pages 1-10 | Accepted 29 Sep 2017, Published online: 07 Oct 2017