Mechanical step variability during treadmill running |
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Authors: | A. Belli J. R. Lacour P. V. Komi R. Candau C. Denis |
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Affiliation: | (1) Laboratoire de Physiologic - GIP Exercice, Faculté de Médecine de Lyon Sud, B.P. 12, F-69921 Oullins, France;(2) Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland;(3) Déparement de Réadaptation Médicale - GIP Exercice, Faculté de Medécine de Saint-Etienne, France;(4) Laboratoire des Sciences du Sport, U.F.R.-S.T.A.P.S., Université de Franche-Comté, Besançon, France;(5) Laboratoire de Physiologic - GIP Exercice, Faculté de Médecine de Saint-Etienne, France |
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Abstract: | The present study was designed to study intra-individual step variability measured both on vertical displacement of the body ( Z) and on step time ( t) parameters by means of a kinematic arm and during treadmill running. A group of 17 subjects ran successively at 60%, 80%, 100% and 140% of their maximal aerobic velocity (vamax). The total number of steps analysed was 6116. The absolute Z step variability (![sgr](/content/x4786637711n6453/xxlarge963.gif) Z) ranged between 5 mm and 21 mm while the absolute t variability (![sgr](/content/x4786637711n6453/xxlarge963.gif) t) ranged between 6 ms and 40 ms. Step variabilities were due to step asymmetry (from 38.5% to 48.5% of the step variability) and to stride variability. For submaximal velocities (60%, 80%, and 100%vamax) both ![sgr](/content/x4786637711n6453/xxlarge963.gif) t and ![sgr](/content/x4786637711n6453/xxlarge963.gif) Z were independent of velocity or body dimensions whereas differences between subjects were significant (P < 0.01) for ![sgr](/content/x4786637711n6453/xxlarge963.gif) Z. On the other hand, variabilities were significantly increased when velocity was changed from submaximal to the 140%vamax level. Furthermore, at submaximal levels ![sgr](/content/x4786637711n6453/xxlarge963.gif) Z was linked to the subject's energy cost of running (P < 0.05). Therefore, the intra-individual step variability should not be neglected in future studies on mechanical efficiency of running and it is suggested that, to obtain a good accuracy (better than 1%,P < 0.05) on mean value and variability of the mechanical parameters, measurements should be performed on at least 32–64 consecutive steps, which corresponds to about 15 to 20 s of running. |
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Keywords: | Treadmill running Step variability symmetry Kinematic arm Energy cost of running |
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