49.4 Thursday, Jan. 5 Center of mass mechanics in the squirrel monkey Saimiri sciureus MILLER, CE*; GRANATOSKY, MC; O'NEILL, MC; BISHOP, KL; SCHMITT, D; Duke; Duke; Stony Brook University; Florida International University; Duke email@example.com
The significance of whole body center of mass mechanics has been well studied in a range of bipedal and quadrupedal animals, but few data exist for primates. Primate quadrupeds exhibit very different locomotor ecologies and mechanics, including limb compliance and protraction, footfall and force distribution patterns when compared to dogs, horses and other terrestrial cursors commonly used as model animals in locomotion studies. Previous work has shown that in many walking animals inverted pendular movements of the center of mass lead to high levels of exchange (recovery) of potential and kinetic energy (PE and KE). Of the primates studied to date the ringtailed lemur, Lemur catta, exhibits recoveries of up to about 70% in walking, much like dogs, while in macaque species values reach up to only about 50%. Here we present the first energy exchange data on a small anthropoid primate, the squirrel monkey, Saimiri sciureus. All three components of ground reaction force were collected for full strides from two animals moving quadrupedally on an instrumented runway. These data were used to calculate fluctuations in PE and KE, and percentage recovery and congruency values. In this sample neither recovery nor congruency correlated with speed. The relationship between percent recovery and percent congruity values was moderately strong, but less pronounced than noted in previous studies. Recovery values were consistent with those seen in macaques. These data add to the growing list of animals, including cats, small mammals and turtles, that present with relatively low recovery values, suggesting that this inverted pendulum mechanism may be relatively restricted to use by terrestrial cursors.