Weighting the Distal Limb Study: Wickler, S.J., Hoyt, D.F., Clayton, H.M., Mullineaux, D.R., Cogger, E.A., Sandoval, E., McGuire, R. and Lopez, C.
The energetic and kinematic consequences of weighting the distal limb. Equine Veterinary Journal 2004; Reason for performing study: It is well known that adding a load to a horse's back increases its energetic costs of locomotion. However the magnitude of the increase resulting from adding the load to the most distal portion of limb has not been measured. Objectives: Oxygen consumption will be measured in horses with mass added to the back and added to the hooves. Because such mass distribution will alter inertial parameters of the limbs, kinematic measurements will be made to quantify the magnitude of change in limb movement. Methods: Steady-state oxygen consumption was measured in 6 horses with a load of 2.4 kg. The load was either carried on the back or equally distributed between the four limbs. Modified bell boots kept the mass at the level of P3. Horses trotted on a treadmill at speeds ranging from 2 to 5 m/s (in 0.5 m/s increments). High-speed (250 Hz) digital images were recorded in a sagittal plane and the positions of retro-reflective markers located on standard positions on the limbs were digitized for kinematic analysis. Results: Loading of the distal limbs produced a 6.7% increase in metabolic rate-an order of magnitude higher than when the mass was added over the back. Although the stride period was 2% longer in horses with loads on the distal limbs, the time of contact and duty factor were not different. Distal limb loading increased the range of motion in hind limbs, but not forelimbs. Conclusions: The costs of swinging the limbs in the horse are considerable and the addition of weights to the distal limb can have a profound effect on not only the energetics of locomotion, but also the kinematics-at least in the hind limb. Potential Relevance: The use of weighted shoes, intended to increase the animation of the gait, will increase the metabolic effort of performance horses a disproportionate amount. The additional mass also increases the joint range of motion and potentially increases the likelihood of injury. Judy http://icehorses.net http://clickryder.com
