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Ground Reaction Forces During Locomotion in Simulated MicrogravitySignificant losses in bone density and mineral, primarily in the lower extremities have been reported following exposure to weightlessness. Recent investigations suggest that mechanical influences such as bone deformation and strain rate may be critically important in stimulating new bone formation. It was hypothesized that velocity, cadence and harness design would significantly affect lower limb impact forces during treadmill exercise in simulated zero gravity (0G). A ground-based hypogravity simulator was used to investigate which factors affect limb loading during tethered treadmill exercise. A fractional factorial design was used and 12 subjects were studied. The results showed that running on active and passive treadmills in the simulator with a tethering force close to the maximum comfortable level produced similar magnitudes for the peak ground reaction force. It was also found that these maximum forces were significantly lower than those obtained during overground trials, even when the speeds of locomotion in the simulator were 66 % greater than those in 1 G. Cadence had no effect on any of the response variables. The maximum rate of force application (DFDT-Max) was similar for overground running and exercise in simulated 0G, provided that the "weightless subjects ran on a motorized treadmill. These findings have implications for the use of treadmill exercise as a countermeasure for hypokinetic osteoporosis. As the relationship between mechanical factors and osteogenesis becomes better understood, results from human experiments in 0G simulators will help to design in-flight exercise programs that are more closely targeted to generate appropriate mechanical stimuli.
Document ID
20000039759
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Davis, B. L.
(Cleveland Clinic Foundation Cleveland, OH United States)
Cavanagh, Peter R.
(Pennsylvania State Univ. University Park, PA United States)
Sommer, H. J., III
(Pennsylvania State Univ. University Park, PA United States)
Wu, G.
(Pennsylvania State Univ. University Park, PA United States)
Date Acquired
August 19, 2013
Publication Date
March 1, 1996
Publication Information
Publication: Aviation, Space and Environmental Medicine
Publisher: Aerospace Medical Association
Volume: 67
Issue: 3
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: NAG5-6199
Distribution Limits
Public
Copyright
Other

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