Biokinetical analysis of the movements of the pelvic limb of the horse and the role of the muscles in the walk and the trot.

The movements of the right hind limb of horses with normal locomotion were studied using cinephotography and electromyography. A model of the cycle of a stride in the walk and the trot was constructed and the kinetic parameters of the segments of the limb were calculated. A good correlation was obtained between the kinetics and the periods of the cycle of a stride during which individual muscles display activity. The results of this study demonstrate that: at placing and lifting, i.e., when a change occurs in the direction of the movement of the limb; b) At the walk, the greatest forces operant at the centres of gravity of the limb segments in the direction of the progression are present in the beginning and the end of the support phase. The first top in the acceleration curve is produced by activity in the retractors of the limb (hamstrings, gluteus medius muscles). At the end of the support phase, when activity in the retractors of the limb no longer exists, the dynamic effect of the moment of the weight about the point of support of the stabilized inclined limb, as well as the elastic resilience of the muscular tissue are responsible for the push-off. At the trot, the greatest forces in the direction of progression are exerted in the middle of the support phase and are largely due to muscular action; c) In the second part of the support phase in the walk, the stifle flexes and the hock extends, which results in stretching the tendinous peroneus tertius and subsequently in flexion of the hock as soon as the hoof starts rolling over; d) The gastrocnemius and cranial tibial muscles in the reciprocal tendinous apparatus centre the line of action of the resultant load on the tibia during the locomotion and reduce the strain due to bending; e) At the end of the support phase, the action of the rectus femoris muscle is replaced by that of the vastus lateralis, which prevents hooking of the patella on the medial ridge of the femoral trochlea by rotating it laterally around a longitudinal axis.