Research article summary (published 30 Jul 1999):

Runners adjust leg stiffness for their first step on a new running surface.

Full Abstract

Human runners adjust the stiffness of their stance leg to accommodate surface stiffness during steady state running. This adjustment allows runners to maintain similar center of mass movement (e.g., ground contact time and stride frequency) regardless of surface stiffness. When runners encounter abrupt transitions in the running surface, they must either make a rapid adjustment or allow the change in the surface stiffness to disrupt their running mechanics. Our goal was to determine how quickly runners adjust leg stiffness when they encounter an abrupt but expected change in surface stiffness that they have encountered previously. Six human subjects ran at 3 m s(-1) on a rubber track with two types of rubber surfaces: a compliant "soft" surface (ksurf = 21.3 kN m(-1) and a non-compliant "hard" surface (ksurf = 533 kN m(-1). We found that runners completely adjusted leg stiffness for their first step on the new surface after the transition. For example, runners decreased leg stiffness by 29% between the last step on the soft surface and the first step on the hard surface (from 10.7 kN m(-1) to 7.6 kN m(-1), respectively). As a result, the vertical displacement of the center of mass during stance ( approximately 7 cm) did not change at the transition despite a reduction in surface compression from 6 cm to less than 0.25 cm. By rapidly adjusting leg stiffness, each runner made a smooth transition between surfaces so that the path of the center of mass was unaffected by the change in surface stiffness.

Author information

Author/s: Ferris, D P (DP); Liang, K (K); Farley, C T (CT);

Affiliation: Department of Integrative Biology, University of California, Berkeley 94720-3140, USA. dferris(-atsign-)ucla.edu

Grants: R29 AR44008 (Agency:NIAMS NIH HHS)

Journal and publication information

Publication Type: Clinical Trial; Journal Article; Randomized Controlled Trial; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.

Journal: Journal of biomechanics (J Biomech), published in UNITED STATES. (Language: eng)

Reference: 1999-Aug; vol 32 (issue 8) : pp 787-94

Dates: Created 1999/09/21; Completed 1999/09/21; Revised 2007/11/14;

PMID: 10433420, status: MEDLINE (last retrieved date: 2/18/2009)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MeSH Headings (categories) shown below.

Adult Biomechanics Computer Simulation Elasticity Exercise Test Female

Gait - physiology Humans Leg - physiology Running - physiology Surface Properties Time Factors

Note: Bold headings indicate primary MeSH headings or qualifiers.

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