Abstract
Dogs are widely recognized as some of the best endurance athletes in the world. Much is known about their physiological specializations for endurance. However, we know much less about their mechanical specializations. One hypothesis is that the forward weight distribution found in dogs and in many other quadrupeds results in the decoupling of vertical and shear force production. In this study, I examine the differential distribution of shear forces between the forelimbs and the hindlimbs of dogs during active shear force production. I use pulling as a loading perturbation in order to achieve variable shear loading without the confounding variables of increasing velocity and altered limb angles that are associated with acceleration and incline studies. The results of this study showed that complete vertical and shear force decoupling between the forelimbs and the hindlimbs does not exist during submaximal shear force production. However, the distribution of propulsive shear force production is heavily biased towards the hindlimbs and remains so throughout active shear force production despite shifts in net shear force production. In addition, the results of this study indicate that the basic mechanics of shear force production are conserved in acceleration, incline locomotion, and pulling.