title: Acceleration capability in elite sprinters and ground impulse: Push more, brake less?
abstract: 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.
authors.affiliation: Laboratory of Human Motricity, Education Sport and Health (EA6312), University of Nice Sophia Antipolis, Nice, France. Electronic address: jean-benoit.morin@unice.fr.
authors.forename: Jean-Benoît
authors.initials: JB
authors.lastname: Morin
authors.affiliation: Research Center in sport and movement (EA 2931), UFR STAPS, University of Paris Ouest Nanterre La Défense, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Slawinski
authors.affiliation: Laboratory "Mouvement, Interactions, Performance" (EA 4334), University of Nantes, France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Dorel
authors.affiliation: Faculty of Sports, University Pablo de Olavide, Seville, Spain.
authors.forename: Eduardo Saez
authors.initials: ES
authors.lastname: de Villareal
authors.affiliation: Research Department, National Institute of Sport, INSEP, Paris, France.
authors.forename: Antoine
authors.initials: A
authors.lastname: Couturier
authors.affiliation: Laboratory of Exercise Physiology (EA 4338), University of Savoy, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Samozino
authors.affiliation: Sports Performance Research Institute New Zealand (SPRINZ), Auckland University of Technology, Auckland, New Zealand.
authors.forename: Matt
authors.initials: M
authors.lastname: Brughelli
authors.affiliation: Research Department, National Institute of Sport, INSEP, Paris, France.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Rabita
mesh_terms: D000054:Acceleration; D054874:Athletic Performance; D001696:Biomechanical Phenomena; D006801:Humans; D008297:Male; D055595:Mechanical Phenomena; D012420:Running; D055815:Young Adult
keywords: Acceleration; Ground reaction force; Running; Sprint start