Doctoral Dissertation Improvement Grant: Energetics and mechanics of quadrupedal walking and running in prosimians

Johns Hopkins University, Baltimore MD

Investigators

Abstract

Energetics has long been an important issue to primatologists and paleoanthropologists interested in the locomotor performance of extant and extinct species. The cost of locomotion, measured per unit distance or per unit time, for example, has been incorporated into various models of resource acquisition, territory defense and migratory behavior. Measurements of the rate of oxygen consumption in several quadrupedal primate species have shown that, like most animals, they exhibit a pattern of increasing metabolic costs with faster speeds and decreasing costs with larger body weight. This study seeks to understand the link between the mechanics and metabolic cost of terrestrial locomotion in quadrupedal primates by focusing on how their limb muscles generate force and modulate energy use during exercise. Quadrupedal primates differ from most other quadrupedal mammals in both their gait characteristics (limb excursion angles) and limb design (muscle mass distribution and muscle-tendon architecture). Recent studies indicate that both of these variables will impact the volume of active muscle that is recruited during locomotion and, because energy use must be set by skeletal muscle activity, will impact the cost of movement. This study will evaluate how the primate muscle-tendon system produces force and how much metabolic energy is consumed in order to generate a unit force. To do this, two separate experiments will be carried out. Metabolic rate during locomotion on the level will be measured for two species of prosimians and compared with previously published data for more cursorial terrestrial mammals. Then, anatomical, video and force-plate data will be collected from one primate species and one similarly sized nonprimate quadrupedal mammal species in order to determine their respective active muscle volumes, joint work and power production during exercise on the level across a range of speeds. This study will be the first to attempt to link the unique aspects of primate locomotion and limb morphology to their metabolic costs. Together, these experiments will generate empirical data testing a fundamental relationship between metabolics and mechanics that is significant for understanding the relationship between energy use and muscle function in primates. The results of this study will provide critical insight into primate biology and provide a physiological basis for understanding the effects of morphological evolution on the energetic cost of locomotion. The broader impacts of this study include the development of a series of computational tools for integrating video and force-plate data from biomechanical studies, which will be made available online to the international community. This work will also create research opportunities for undergraduates at Johns Hopkins University. These students will be included in aspects of metabolic, kinematic and force-plate data collection and analysis as well as computer programming, providing an interdisciplinary experience that spans the biological and physical sciences.