Stability and the time-dependent structure of gait variability in walking and running Kimberlee Jordan a, * , John H. Challis b , Joseph P. Cusumano c , Karl M. Newell b a Department of Integrative Physiology, The University of Colorado, Carlson 202G, 354 UCB Boulder, CO 80309, USA b Department of Kinesiology, The Pennsylvania State University, 266 Recreation Building, University Park, PA 16802, USA c Department of Engineering Science and Mechanics, The Pennsylvania State University, 0212 Earth and Engineering Sciences Building, University Park, PA 16802, USA article info PsycINFO classification: 2330 Keywords: Locomotion Stability Variability Fluctuation Analysis (DFA) Gait transition abstract Participants were asked to walk and run continuously (5 min trials) at speeds associated with preferred gait transition speeds. During slow running the local dynamic stability of the head was decreased compared with fast walking, with the reverse being true for the local dynamic stability of the ankle. The standard deviation of rel- ative phase of the knee and ankle also was greater during slow run- ning than fast walking. These findings for stability were mirrored in the detrended fluctuation analysis of the peak to peak interval of the head and ankle. Taken collectively these results support the proposition that larger long range correlations in the stride interval are associated with decreases in measures of stability. Ó 2008 Published by Elsevier B.V. 1. Introduction It has been suggested that walking and running at speeds at and around preferred transition speeds can have a destabilizing effect on the respective gait cycle (e.g., Brisswalter & Mottet, 1996; Diedrich & Warren, 1995; Diedrich & Warren, 1998). It has also been shown that the strength of long range cor- relations in the stride intervals of both walking and running (Jordan, Challis, & Newell, 2006; Jordan, Challis, & Newell, 2007a; 2007b) is speed dependent. At the preferred speed (in either walking or run- ning), long range correlations are weaker than at slower or faster than preferred speeds. The purpose of this study is to examine the relation between long range correlations of the stride interval and mea- sures of stability in walking and running. 0167-9457/$ - see front matter Ó 2008 Published by Elsevier B.V. doi:10.1016/j.humov.2008.09.001 * Corresponding author. Tel.: +1 303 492 4568; fax: +1 303 492 6778. E-mail address: kimberlee.jordan@colorado.edu (K. Jordan). Human Movement Science xxx (2008) xxx–xxx Contents lists available at ScienceDirect Human Movement Science journal homepage: www.elsevier.com/locate/humov ARTICLE IN PRESS Please cite this article in press as: Jordan, K., et al. Stability and the time-dependent structure of gait ... Human Movement Science (2008), doi:10.1016/j.humov.2008.09.001