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J Biomech. 2015 Sep 18;48(12):3149-54. doi: 10.1016/j.jbiomech.2015.07.009. Epub 2015 Jul 17.

Acceleration capability in elite sprinters and ground impulse: Push more, brake less?

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Laboratory of Human Motricity, Education Sport and Health (EA6312), University of Nice Sophia Antipolis, Nice, France. Electronic address:
Research Center in sport and movement (EA 2931), UFR STAPS, University of Paris Ouest Nanterre La Défense, France.
Laboratory "Mouvement, Interactions, Performance" (EA 4334), University of Nantes, France.
Faculty of Sports, University Pablo de Olavide, Seville, Spain.
Research Department, National Institute of Sport, INSEP, Paris, France.
Laboratory of Exercise Physiology (EA 4338), University of Savoy, France.
Sports Performance Research Institute New Zealand (SPRINZ), Auckland University of Technology, Auckland, New Zealand.


Overground sprint studies have shown the importance of net horizontal ground reaction force impulse (IMPH) for acceleration performance, but only investigated one or two steps over the acceleration phase, and not in elite sprinters. The main aim of this study was to distinguish between propulsive (IMPH+) and braking (IMPH-) components of the IMPH and seek whether, for an expected higher IMPH, faster elite sprinters produce greater IMPH+, smaller IMPH-, or both. Nine high-level sprinters (100-m best times range: 9.95-10.60s) performed 7 sprints (2×10 m, 2×15 m, 20 m, 30 m and 40 m) during which ground reaction force was measured by a 6.60 m force platform system. By placing the starting-blocks further from the force plates at each trial, and pooling the data, we could assess the mechanics of an entire "virtual" 40-m acceleration. IMPH and IMPH+ were significantly correlated with 40-m mean speed (r=0.868 and 0.802, respectively; P<0.01), whereas vertical impulse and IMPH- were not. Multiple regression analyses confirmed the significantly higher importance of IMPH+ for sprint acceleration performance. Similar results were obtained when considering these mechanical data averaged over the first half of the sprint, but not over the second half. In conclusion, faster sprinters were those who produced the highest amounts of horizontal net impulse per unit body mass, and those who "pushed more" (higher IMPH+), but not necessarily those who also "braked less" (lower IMPH-) in the horizontal direction.


Acceleration; Ground reaction force; Running; Sprint start

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