The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)


Stance and swing phase joint mechanics in chimpanzee bipedal walking

MATTHEW C. O'NEILL1, LENG-FENG LEE2, BRIGITTE DEMES1, NATHAN THOMPSON1, SUSAN G. LARSON1, JACK T. STERN, JR.1 and BRIAN R. UMBERGER2.

1Department of Anatomical Sciences, Stony Brook University School of Medicine, 2Department of Kinesiology, University of Massachusetts Amherst

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Humans are known to be exceptional bipedal walkers, having considerably lower locomotor costs than our closest living relative, the chimpanzee. The lower locomotor costs in humans should, in part, be attributable to differences in how hind limb joints produce and absorb mechanical energy across a stride. However, the mechanical work and power requirements of the chimpanzee gait cycle are still poorly defined. Here, we present new data on the joint work and power output of the chimpanzee hind limb across stance and swing phases of a bipedal stride.

Synchronized video and force plate data were collected from three chimpanzees (Pan troglodytes) walking bipedally along an overground runway. Three-dimensional marker positions and ground forces were then integrated with scaled, subject-specific chimpanzee musculoskeletal models. These models were used to solve for hip, knee and ankle work and power output over a full stride cycle in OpenSimTM.

Initial results indicate that, like humans, the hip and ankle are the primary sources of mechanical energy generation over a stride in bipedal chimpanzees, while the knee is the major energy sink. However, chimpanzees attribute a larger fraction of their total joint power to limb swing than do humans. Thus, limb-swing mechanics may contribute to the reported differences in the energy cost of walking between these species. Taken together these data provide new insights into the joint-level mechanics of chimpanzee bipedalism, which will lead to a better understanding of adaptations for habitual bipedal locomotion.

Supported by NSF BCS-0935321 and NSF BCS-0935327

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