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First published online January 30, 2009
Journal of Experimental Biology 212, 550-565 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.018093

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Exploring the mechanical basis for acceleration: pelvic limb locomotor function during accelerations in racing greyhounds (Canis familiaris)

S. B. Williams^1,*, J. R. Usherwood², K. Jespers², A. J. Channon² and A. M. Wilson²

¹ Department of Veterinary Preclinical Sciences, Faculty of Veterinary Science, The University of Liverpool, Liverpool, UK
² Structure and Motion Laboratory, The Royal Veterinary College, North Mymms, Hertfordshire, UK

^* Author for correspondence (e-mail: s.b.williams{at}liverpool.ac.uk)

Accepted 25 November 2008

Animals in their natural environments are confronted with a regular need to perform rapid accelerations (for example when escaping from predators or chasing prey). Such acceleration requires net positive mechanical work to be performed on the centre of mass by skeletal muscle. Here we determined how pelvic limb joints contribute to the mechanical work and power that are required for acceleration in galloping quadrupeds. In addition, we considered what, if any, biomechanical strategies exist to enable effective acceleration to be achieved. Simultaneous kinematic and kinetic data were collected for racing greyhounds undergoing a range of low to high accelerations. From these data, joint moments and joint powers were calculated for individual hindlimb joints. In addition, the mean effective mechanical advantage (EMA) of the limb and the `gear ratio' of each joint throughout stance were calculated. Greatest increases in joint work and power with acceleration appeared at the hip and hock joints, particularly in the lead limb. Largest increases in absolute positive joint work occurred at the hip, consistent with the hypothesis that quadrupeds power locomotion by torque about the hip. In addition, hindlimb EMA decreased substantially with increased acceleration – a potential strategy to increase stance time and thus ground impulses for a given peak force. This mechanism may also increase the mechanical advantage for applying the horizontal forces necessary for acceleration.

Key words: acceleration, greyhound, power, biomechanics, locomotion, effective mechanical advantage

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				S. B. Williams, H. Tan, J. R. Usherwood, and A. M. Wilson Pitch then power: limitations to acceleration in quadrupeds Biol Lett, October 23, 2009; 5(5): 610 - 613. [Abstract] [Full Text] [PDF]