Newman, D.J., Alexander, H.L., and Webbon, B.W., "Energetics and Mechanics for Partial Gravity Locomotion," Aviat. Space and Environ. Med., 65: 815-823, 1994.
Human biodynamic movement is investigated for locomotion over the continuum of gravitational acceleration from Earth-normal gravity (1 G) through lunar gravity (1/6 G). Human evolution in an Earth-normal 1 G environment and the development of our 1 G musculoskeletal system have presumably optimized performance for terrestrial locomotion, and the mechanics of low gravity locomotion are not clearly understood. Using a mass-spring system, the mechanics of locomotion across the continuum of gravity are modeled. Experimental results obtained during underwater simulation and parabolic flight for ambulatory tasks under conditions of reduced gravity are detailed elsewhere [16, 17] and used herein to validate the analytical modeling effort. It was hypothesized that the linear mass-spring model could account for some of the dynamic changes that take place during partial gravity running. Results indicate the leg spring stiffness is not significantly changed due to gravity or forward speed. This fundamental finding serves as an input to the model which results in significant reductions in peak force for low gravity locomotion as compared to 1 G running and significant reductions in dimensionless vertical stiffness at reduced gravity and lower forward speeds. The model is unable to correctly predict the leg angle upon ground contact for intermediate (1.5 m/s) speeds. Results verify a change in the mechanics of locomotion for partial gravity environments, implying an unique ability of humans to accommodate to altered gravitational fields.
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