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First published online March 12, 2009
Journal of Experimental Biology 212, 1053-1063 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.020248

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Function of the epaxial muscles during trotting

Nadja Schilling^1,* and David R. Carrier²

¹ Institute of Systematic Zoology and Evolutionary Biology, Friedrich-Schiller-University, Erbertstrasse 1, 07743 Jena, Germany
² Department of Biology, 201 South Biology Building, University of Utah, Salt Lake City, UT 84112, USA

^* Author for correspondence (e-mail: nadja.schilling{at}uni-jena.de)

Accepted 19 January 2009

In mammals, the epaxial muscles are believed to stabilize the trunk during walking and trotting because the timing of their activity is not appropriate to produce bending of the trunk. To test whether this is indeed the case, we recorded the activity of the m. multifidus lumborum and the m. longissimus thoracis et lumborum at three different sites along the trunk (T13, L3, L6) as we manipulated the moments acting on the trunk and the pelvis in dogs trotting on a treadmill. Confirming results of previous studies, both muscles exhibited a biphasic and bilateral activity. The higher burst was associated with the second half of ipsilateral hindlimb stance phase, the smaller burst occurred during the second half of ipsilateral hindlimb swing phase. The asymmetry was noticeably larger in the m. longissimus thoracis et lumborum than in the m. multifidus lumborum. Although our manipulations of the inertia of the trunk produced results that are consistent with previous studies indicating that the epaxial muscles stabilize the trunk against accelerations in the sagittal plane, the responses of the epaxial muscles to manipulations of trunk inertia were small compared with their responses when moments produced by the extrinsic muscles of the hindlimb were manipulated. Our results indicate that the multifidus and longissimus muscles primarily stabilize the pelvis against (1) vertical components of hindlimb retractor muscles and (2) horizontal components of the hindlimb protractor and retractor muscles. Consistent with this, stronger effects of the manipulations were observed in the posterior sampling sites.

Key words: electromyogram, EMG, Canis, longissimus, multifidus, trunk, mammals, dog

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This article has been cited by other articles:

				N. Schilling, T. Fischbein, E. P. Yang, and D. R. Carrier Function of the extrinsic hindlimb muscles in trotting dogs J. Exp. Biol., April 1, 2009; 212(7): 1036 - 1052. [Abstract] [Full Text] [PDF]