Faster top running speeds are achieved with greater ground forces not more rapid leg
movements.
Weyand, Peter G., Deborah B. Sternlight, Matthew J. Bellizzi, and Seth Wright.
Harvard University, Museum of Comparative Zoology, Bedford, Massachusetts
01730
APStracts 7:0438A, 2000.
We twice tested the hypothesis that top running speeds are determined by the amount of
force applied to the ground rather than how rapidly limbs are repositioned in the air. First,
we compared the mechanics of 33 subjects of different sprinting abilities running at their
top speeds on a level treadmill. Second, we compared the mechanics of declined
(«minus»6°) and inclined (+9°) top-speed treadmill running in five subjects. For both
tests, we used a treadmill-mounted force plate to measure the time between stance
periods of the same foot (swing time, tsw) and the force applied to the running surface at
top speed. To obtain the force relevant for speed, the force applied normal to the ground
was divided by the weight of the body (Wb) and averaged over the period of foot-ground
contact period (Favge/Wb). The top speeds of the 33 subjects who completed the level
treadmill protocol spanned a 1.8-fold range from 6.2 to 11.1 m/s. Among these subjects,
the regression of Favge/Wb on top speed indicated that this force was 1.26 times greater
for a runner with a top speed of 11.1 vs. 6.2 m/s. In contrast, the time taken to swing the
limb into position for the next step (tsw) did not vary (P = 0.18). Declined and inclined
top speeds differed by 1.4-fold (9.96 ± 0.3 vs. 7.10 ± 0.3 m/s, respectively), with the
faster declined top speeds being achieved with mass-specific support forces that were 1.3
times greater (2.30 ± 0.06 vs. 1.76 ± 0.04 Wb) and minimum tsw that were similar
(+8%). We conclude that human runners reach faster top speeds not by repositioning their
limbs more rapidly in the air, but by applying greater support forces to the ground.
Received 15 March 2000; accepted in final form 6 September 2000
APS Manuscript Number A266-0.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2000 The American Physiological Society.
Published in APStracts on 15 September 2000