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

First published online November 28, 2008
Journal of Experimental Biology 211, 3889-3907 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.020578

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 Google Scholar Google Scholar Articles by Dunbar, D. C. Articles by Zarcades, A. Search for Related Content PubMed PubMed Citation Articles by Dunbar, D. C. Articles by Zarcades, A. Social Bookmarking                         What's this?

Stabilization and mobility of the head, neck and trunk in horses during overground locomotion: comparisons with humans and other primates

Donald C. Dunbar^1,*, Jane M. Macpherson², Roger W. Simmons³ and Athina Zarcades³

¹ Department of Anatomy and Neurobiology, and Caribbean Primate Research Center, University of Puerto Rico School of Medicine, PO Box 365067, San Juan, PR 00936, USA
² Neurological Sciences Institute, Oregon Health and Science University, 505 NW 185th Avenue, Beaverton, OR 97006, USA
³ School of Exercise and Nutritional Sciences, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA

^* Author for correspondence (e-mail: ddunbar{at}rcm.upr.edu)

Accepted 13 October 2008

Segmental kinematics were investigated in horses during overground locomotion and compared with published reports on humans and other primates to determine the impact of a large neck on rotational mobility (>20 deg.) and stability (20 deg.) of the head and trunk. Three adult horses (Equus caballus) performing walks, trots and canters were videotaped in lateral view. Data analysis included locomotor velocity, segmental positions, pitch and linear displacements and velocities, and head displacement frequencies. Equine, human and monkey skulls and cervical spines were measured to estimate eye and vestibular arc length during head pitch displacements. Horses stabilized all three segments in all planes during all three gaits, unlike monkeys and humans who make large head pitch and yaw rotations during walks, and monkeys that make large trunk pitch rotations during gallops. Equine head angular displacements and velocities, with some exceptions during walks, were smaller than in humans and other primates. Nevertheless, owing to greater off-axis distances, orbital and vestibular arc lengths remained larger in horses, with the exception of head–neck axial pitch during trots, in which equine arc lengths were smaller than in running humans. Unlike monkeys and humans, equine head peak-frequency ranges fell within the estimated range in which inertia has a compensatory stabilizing effect. This inertial effect was typically over-ridden, however, by muscular or ligamentous intervention. Thus, equine head pitch was not consistently compensatory, as reported in humans. The equine neck isolated the head from the trunk enabling both segments to provide a spatial reference frame.

Key words: quadrupedal, bipedal, walk, trot, canter, kinematics, sensorimotor control, vision, vestibular, spatial orientation, navigation, reference frames, inertia, pitch rotation, linear displacement, velocity, Equus caballus, Homo, Hylobates, Cercopithecus, Macaca, Semnopithecus

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