The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Investigating causal relationships among morphology, kinematics and energetics of bipedal locomotion using musculoskeletal models: forward and inverse dynamic approaches


1Department of Mechanical Engineering, Keio University, 2Department of Zoology, Kyoto University

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Understanding how differences in morphology and structure of musculoskeletal system affect mechanics and energetics of bipedal walking in human and non-human primates provides valuable insights towards clarifying the origin and evolution of human bipedal walking. However, elucidating the complete mechanisms of bipedal walking based solely on experimental analyses is not trivial. Therefore, we recently employ computational techniques to investigate causal relationships among morphology, kinematics and energetics of bipedal locomotion based on musculoskeletal models.

For forward dynamic simulation, we constructed a 2D neuro-musculoskeletal model of bipedal walking in Japanese macaque. We used phase oscillators as a model of spinal pattern generator. By optimizing the parameters defining the timing and magnitude of motor command send to each muscle such as to maximize walking distance and to minimize energetic cost of locomotion, continuous bipedal walking was successfully simulated. This approach allows complete prediction of locomotion based on a given musculoskeletal model, but extension of this simulation to 3D is currently very difficult.

For this reason, we also used inverse dynamics analysis. An anatomically-based 3D musculoskeletal model was constructed and joint motions and ground-reaction-forces from experiments were input to estimate muscle forces and energetic cost of locomotion. Although kinematics of locomotion must be predetermined, this approach allows evaluation of effects of differences in musculoskeletal morphology on energetic cost of locomotion. Forward and inverse dynamic approaches have both advantages and disadvantages, but complementary use of two approaches could provide profound insights into the evolution of human bipedalism.

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