Effects of speed on forelimb joint angular displacement patterns in vervet monkeys (Cercopithecus aethiops).

Shoulder, elbow and wrist joint angular displacement patterns were analyzed for five vervet monkeys across increasing speed. Within symmetrical gaits, the peak positions of the pattern for each joint tended to decrease with increasing speed as did the yield angle of the elbow (more "yielding"). Across the walk(run)-gallop transition there were no notable changes in the displacement patterns, but there was a consistent decrease in the range of elbow movements and an increase in the yield angle. Across symmetrical gaits, there was also a tendency for some of the peak positions to decrease. These results are compared with those available for cats and dogs, and are interpreted relative to functional and neurological aspects of forelimb movements in primates.