GAITS OF HORSES - ARE THEY RULED BY OSCIL LATIONS .2. TROT AND GALLOPARE DETERMINED BY SPRING MECHANISMS

For a basic understanding of the gaits of horses, the mechanical princ iples for the analyses of oscillations are essential. They can be used as efficient tools for diagnostic purposes. Movements, forces and mom ents acting during locomotion are predictable using rather simple comp utational models. In the model proposed here, the extremities move lik e pendula. During ground contact they additionally are compressed like springs. The body segment composed of head, neck and thorax performs bending oscillations in relation to the lumbo-sacral segment. Standard gaits make use of these components with different intensities: The wa lk is governed by resonant oscillations of the pendula formed by the e xtremities. At higher velocities, spring effects in individual legs le gs are of growing importance. In the trot, the movements of the legs a re too fast to be explained by the mechanisms of resonant pendula. Pow er expenditure is minimized by temporary storage of elastic energy in the legs' ''springs''. During ground contract two legs in parallel arr angement (the active diagonal) determine the resonance frequency (and thus the trot frequency). Gallop makes use of up to three ''springs'' at the same rime. In addition, energy is stored in the bended beam (or spring) of the trunk.