DEMES, Brigitte; FRANZ, Theresa M.; CARLSON, Kristian J.; Stony Brook University; Stony Brook University; Stony Brook University: Differential force distribution on the fore- and hind limbs of strepsirrhine primates

Primates usually carry more weight with their hind limbs than forelimbs, whereas the opposite tends to be true for nonprimate mammals. This has been interpreted as an adaptation to arboreal locomotion on flexible branches and has also been related to the non-locomotory functions of the primate forelimb in grasping and manipulating. We tested whether this differential force distribution is true for two species of strepsirrhine primates that are closer to the basal primate condition than the anthropoid species previously analyzed. Three individuals each of Lemur catta and Eulemur fulvus performed long jumps to and from a force plate and walked and ran over the plate integrated into a wooden runway. In general, vertical force peaks and impulses are higher for the hind limbs than for the forelimbs for the jumps as well as in overground locomotion. Whereas L. catta landed with hind limbs first, E. fulvus frequently made first contact with the forelimbs. In these cases, the forelimb forces and impulses were higher. Braking and propulsive forces were low in comparison to the vertical forces and impulses, and confirmed previous findings for primate and nonprimate mammals that the major propulsive thrust is coming from the rear. Our data partially support the notion that the forelimb of primates is spared high forces. Supported by NSF BCS019331