Palmar and Plantar Pressure While Walking on a Horizontal Ladder and Single Pole in Macaca fuscata

Abstract

To investigate biomechanical function in the hand and foot during quadrupedal locomotion in nonhuman primates, physical anthropologists and primatologists measure the pressure under them. We collected hand and foot pressure data while a Japanese macaque (Macaca fuscata), a semiterrestrial anthropoid, walked on 2 different simulated arboreal substrates, a horizontal ladder and a single pole, to explore differences in hand and foot use between the 2 substrates. The ladder rungs were perpendicular to the craniocaudal axis of the subject, and the pole was parallel to the subject’s craniocaudal axis. We tested the hypothesis that the pole was a more challenging substrate for the macaque than the ladder. Focusing on a diagonal sequence, diagonal couplets gait, we calculated gait characteristics and computed mean peak-pressure images of the hand and foot for each substrate from individual peak images via translation registration. We found several substrate differences that supported the hypothesis. The Japanese macaque walked at significantly slower speeds when traveling on the pole than on the ladder. Slower travel speed on the pole suggests that the Japanese macaque needed a wider support base to maintain balance on this substrate. Mean peak-pressure images suggest that the ladder invoked a more stepping-like behavior, but the pole invoked a more grasping-like behavior, especially of the foot. We show that the hand and foot use of the Japanese macaque would be adaptable to biomechanical challenges posed by different substrates.