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

First published online April 8, 2004
Journal of Experimental Biology 207, 1715-1728 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00947

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 Lee, D. V. Articles by Carrier, D. R. Search for Related Content PubMed PubMed Citation Articles by Lee, D. V. Articles by Carrier, D. R.

Effects of mass distribution on the mechanics of level trotting in dogs

David V. Lee^*, Eric F. Stakebake, Rebecca M. Walter and David R. Carrier

Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112-0840, USA

^* Author for correspondence at present address: Concord Field Station, Department of Organismic and Evolutionary Biology, Harvard University, Bedford, MA 01730, USA (e-mail: dlee{at}oeb.harvard.edu)

Accepted 16 February 2004

The antero–posterior mass distribution of quadrupeds varies substantially amongst species, yet the functional implications of this design characteristic remain poorly understood. During trotting, the forelimb exerts a net braking force while the hindlimb exerts a net propulsive force. Steady speed locomotion requires that braking and propulsion of the stance limbs be equal in magnitude. We predicted that changes in body mass distribution would alter individual limb braking–propulsive force patterns and we tested this hypothesis by adding 10% body mass near the center of mass, at the pectoral girdle, or at the pelvic girdle of trotting dogs. Two force platforms in series recorded fore- and hindlimb ground reaction forces independently. Vertical and fore–aft impulses were calculated by integrating individual force–time curves and Fourier analysis was used to quantify the braking–propulsive (b–p) bias of the fore–aft force curve. We predicted that experimental manipulation of antero–posterior mass distribution would (1) change the fore–hind distribution of vertical impulse when the limb girdles are loaded, (2) decrease the b–p bias of the experimentally loaded limb and (3) increase relative contact time of the experimentally loaded limb, while (4) the individual limb mean fore–aft forces (normalized to body weight + added weight) would be unaffected. All four of these results were observed when mass was added at the pelvic girdle, but only 1, 3 and 4 were observed when mass was added at the pectoral girdle. We propose that the observed relationship between antero–posterior mass distribution and individual limb function may be broadly applicable to quadrupeds with different body types. In addition to the predicted results, our data show that the mechanical effects of adding mass to the trunk are much more complex than would be predicted from mass distribution alone. Effects of trunk moments due to loading were evident when mass was added at the center of mass or at the pelvic girdle. These results suggest a functional link between appendicular and axial mechanics via action of the limbs as levers.

Key words: locomotion, running, dog, Canis, force, braking, propulsion, center of mass, limb, trunk

This article has been cited by other articles:

				D. V. Lee, M. P. McGuigan, E. H. Yoo, and A. A. Biewener Compliance, actuation, and work characteristics of the goat foreleg and hindleg during level, uphill, and downhill running J Appl Physiol, January 1, 2008; 104(1): 130 - 141. [Abstract] [Full Text] [PDF]

				A. V. Kharlamova, L. N. Trut, D. R. Carrier, K. Chase, and K. G. Lark Genetic regulation of canine skeletal traits: trade-offs between the hind limbs and forelimbs in the fox and dog Integr. Comp. Biol., September 1, 2007; 47(3): 373 - 381. [Abstract] [Full Text] [PDF]

				H. Pontzer Predicting the energy cost of terrestrial locomotion: a test of the LiMb model in humans and quadrupeds J. Exp. Biol., February 1, 2007; 210(3): 484 - 494. [Abstract] [Full Text] [PDF]

				A. R. Lammers, K. D. Earls, and A. R. Biknevicius Locomotor kinetics and kinematics on inclines and declines in the gray short-tailed opossum Monodelphis domestica J. Exp. Biol., October 15, 2006; 209(20): 4154 - 4166. [Abstract] [Full Text] [PDF]

				J. J. Chen, A. M. Peattie, K. Autumn, and R. J. Full Differential leg function in a sprawled-posture quadrupedal trotter J. Exp. Biol., January 15, 2006; 209(2): 249 - 259. [Abstract] [Full Text] [PDF]

				H. Pontzer A new model predicting locomotor cost from limb length via force production J. Exp. Biol., April 15, 2005; 208(8): 1513 - 1524. [Abstract] [Full Text] [PDF]