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Lisa PowersAdvisor: Karen Steudel Contact Information: Web page: Hominin Locomotion Lab Research Interests: Effects of Arm Swing on the Energetic Cost of Human WalkingMy research focuses on the role of the upper limbs in human walking. When early hominins made the transition from quadrupedal to bipedal locomotion, how did energetic cost constrain the evolution of upper limb morphology? Do inertial properties of the free-swinging upper limb help minimize the energetic cost of human locomotion, or are they simply “extra baggage” that must be transported? A particular inertial property of interest is the natural pendular period (NPP). NPP is the period at which a given pendulum requires the least amount of energy to maintain its swing. For a compound pendulum such as a limb, this period is determined by the limb’s mass, center of mass and moment of inertia. Previous research in the field of locomotor biomechanics and energetics has indicated that mass distribution along the limbs of quadruped mammals results in very similar pendular periods for forelimbs and hindlimbs, despite great differences in limb length, mass, and morphology. It is hypothesized that forelimb and hindlimb NPPs converge on all quadrupeds because it is the most energy efficient arrangement. It is also known that humans swing their upper limbs in phase with lower limbs during locomotion. This suggests that hominid upper and lower limbs should retain similar NPPs in order to maximize locomotor economy, but this would require that upper limbs be especially massive at their distal ends in order to have NPPs equivalent to the much longer, more massive lower limbs. It remains unclear whether the theoretical minimization of mechanical work from similar upper and lower limb NPPs would result in a significant reduction in locomotor cost, or if the mass of the arms alone is primarily responsible for locomotor costs associated with the upper limbs. I am currently engaged in experimental research that compares energetic cost (via measurement of volume of oxygen consumption) on human subjects with mass added to simulate various pairings of upper and lower limb NPPs to gain insight into these questions. |
