Force, Motion, Speed: A grounded perspective on human running performance: Research has resolved the controversy over what prevents an athlete from sprinting faster once “0” accleration is attained. Previous logic supporting horizontally-directed force as the main factor preventing increased velocity at maximum speed does not hold up. Numerous studies have now identified the main factors limiting an athlete’s maximum (MPH) sprinrting speed.
Nagahara, et. al. (2017) conducted a well designed stucy to clarify the mechanical determinants of sprinting performance during acceleration and maximal speed phases of a single sprint, using ground reaction forces (GRFs). While 18 male athletes performed a 60-m sprint, GRF was measured at every step over a 50-m distance from the start. Variables during the entire acceleration phase were approximated with a fourth-order polynomial. Subsequently, accelerations at 55%, 65%, 75%, 85%, and 95% of maximal speed, and running speed during the maximal speed phase were determined as sprinting performance variables. Ground reaction impulses and mean GRFs during the acceleration and maximal speed phases were selected as independent variables. Stepwise multiple regression analysis selected propulsive and braking impulses as contributors to acceleration at 55%–95% (β > 0.724) and 75%–95% (β > 0.176), respectively, of maximal speed. Moreover, mean vertical force was a contributor to maximal running speed (β = 0.481). The current results demonstrate that exerting a large propulsive force during the entire acceleration phase, suppressing braking force when approaching maximal speed, and producing a large vertical force during the maximal speed phase are essential for achieving greater acceleration and maintaining higher maximal speed, respectively.
*Coaching Application: While ground reaction forces in both directions are important and require separate and unique strength and neuromuscular training programs and exercises, the critical factor preventing an increase in maximum velocity is the inability to exert additional vertically-directed force to the ground to counter braking force and propel the body back up into the area in the shortest period of time.
NASE members can access the Sports Speed Digest Archives for numerous articles describing specific exercises designed to increase both vertically- and horizontally-directed ground reaction force.
Ryu Nagahara, Mirai Mizutani, Akifumi Matsuo, Hiroaki Kanehisa, and Tetsuo Fukunaga. 2017. Association of sprint performance with ground reaction forces during acceleration and maximal speed phases in a single sprint. J Appl Biomech. Sep 27:1-20. doi: 10.1123/jab.2016-0356.