Meeting Abstract

P3.189  Sunday, Jan. 6  Whole-body mechanics of arboreal locomotion in primates: integrating gait parameters, limb compliance and weight distribution. SCHMIDT, M.; Friedrich Schiller University, Jena, Germany schmidt.manuela@uni-jena.de

The diversity of locomotor parameters in quadruped primates offers the potential to explore how variations in footfall sequence, limb compliance, and limb forces influence the efficiency of energy recovery from fluctuations in gravitational potential (EP) and kinetic energy (EK). By comparing four species of small, arboreal primates, this study examines whether the principles of arboreal quadruped walking are compatible with principles that are involved in mechanical energy-saving mechanisms. It turns out that variations in footfall sequence largely determine the phase relationships between fluctuations in EP and EK, but only affect the efficiency of energy recovery to a minor degree. The amplitudes of change in EP and EK differ considerably, however, making the level of energy recovery very low, in the range of zero to 20%. Differences among the species are explained by differences in limb stiffness and in weight distribution between the fore- and hindlimbs. In pygmy lorises, limb stiffness is high, thus generating significant changes in EP. Lorises thus recover a considerable amount of energy from vertical oscillations of the centre of mass. Cotton-top tamarins and squirrel monkeys largely avoid these vertical oscillations and confirm the prediction that compliant limb kinematics distribute limb forces more evenly throughout the stride cycle. Amplitudes of change in EP only account for 1% of changes in EK in these species. Mouse lemurs resemble other small mammals such as opossums in their locomotor mechanics and therefore likely represent a condition close to that assumed for the last common ancestor of primates.