QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online March 8, 2005
Journal of Experimental Biology 208, 799-808 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01435

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Neptune, R. R. Articles by Sasaki, K. Search for Related Content PubMed PubMed Citation Articles by Neptune, R. R. Articles by Sasaki, K. Social Bookmarking                         What's this?

Ankle plantar flexor force production is an important determinant of the preferred walk-to-run transition speed

Richard R. Neptune^* and Kotaro Sasaki

Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78712, USA

^* Author for correspondence (e-mail: rneptune{at}mail.utexas.edu)

Accepted 13 December 2004

The mechanisms that govern the voluntary transition from walking to running as walking speed increases in human gait are not well understood. The objective of this study was to examine the hypothesis that plantar flexor muscle force production is greatly impaired at the preferred transition speed (PTS) due to intrinsic muscle properties and, thus, serves as a determinant for the walk-to-run transition. The plantar flexors have been shown to be important contributors to satisfying the mechanical energetic demands of walking and are the primary contributors to the observed ground reaction forces (GRFs) during the propulsion phase. Thus, if the plantar flexor force production begins to diminish near the PTS despite an increase in muscle activation, then a corresponding decrease in the GRFs during the propulsion phase would be expected. This expectation was supported. Both the peak anterior/posterior and vertical GRFs decreased during the propulsion phase at walking speeds near the PTS. A similar decrease was not observed during the braking phase. Further analysis using forward dynamics simulations of walking at increasing speeds and running at the PTS revealed that all lower extremity muscle forces increased with walking speed, except the ankle plantar flexors. Despite an increase in muscle activation with walking speed, the gastrocnemius muscle force decreased with increasing speed, and the soleus force decreased for walking speeds exceeding 80% PTS. These decreases in force production were attributed to the intrinsic force–length–velocity properties of muscle. In addition, the running simulation analysis revealed that the plantar flexor forces nearly doubled for similar activation levels when the gait switched to a run at the PTS due to improved contractile conditions. These results suggest the plantar flexors may serve as an important determinant for the walk-to-run transition and highlight the important role intrinsic muscle properties play in determining the specific neuromotor strategies used in human locomotion.

Key words: gait, intrinsic muscle properties, modeling and simulation

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				K. Sasaki, R. R. Neptune, and S. A. Kautz The relationships between muscle, external, internal and joint mechanical work during normal walking J. Exp. Biol., March 1, 2009; 212(5): 738 - 744. [Abstract] [Full Text] [PDF]

				J. L. Bartlett and R. Kram Changing the demand on specific muscle groups affects the walk-run transition speed J. Exp. Biol., April 15, 2008; 211(8): 1281 - 1288. [Abstract] [Full Text] [PDF]

				D. D. Marciniuk, S. J. Butcher, J. K. Reid, G. F. MacDonald, N. D. Eves, R. Clemens, and R. L. Jones The Effects of Helium-Hyperoxia on 6-min Walking Distance in COPD: A Randomized, Controlled Trial Chest, June 1, 2007; 131(6): 1659 - 1665. [Abstract] [Full Text] [PDF]

				V. Segers, P. Aerts, M. Lenoir, and D. De Clerq Dynamics of the body centre of mass during actual acceleration across transition speed J. Exp. Biol., February 15, 2007; 210(4): 578 - 585. [Abstract] [Full Text] [PDF]

				G. Cappellini, Y. P. Ivanenko, R. E. Poppele, and F. Lacquaniti Motor Patterns in Human Walking and Running J Neurophysiol, June 1, 2006; 95(6): 3426 - 3437. [Abstract] [Full Text] [PDF]

				R. L. Marsh, D. J. Ellerby, H. T. Henry, and J. Rubenson The energetic costs of trunk and distal-limb loading during walking and running in guinea fowl Numida meleagris: I. Organismal metabolism and biomechanics J. Exp. Biol., June 1, 2006; 209(11): 2050 - 2063. [Abstract] [Full Text] [PDF]