Accuracy of aimed arm movements in changed gravity.
We studied the accuracy of aimed arm movements in normal gravity, and during the hypergravity (hyper-G) and microgravity (micro-G) episodes of KC-135 parabolic flights. Subjects pointed at mirror-viewed targets without sight of their arm, and final pointing position was measured by a digitizing pad. Compared with the normal gravity (normal-G) baseline, subjects pointed consistently higher in hyper-G, and still higher in micro-G. Results were not different if subjects viewed targets only during normal-G and pointed at their memorized position under changed gravity (changed-G); this suggests that the "elevator illusion" played a minor role in our study. The observed impairments were attributed to degraded proprioceptive feedback and/or inappropriate motor programs in changed-G. Pointing accuracy improved movement-to-movement but not parabola-to-parabola, indicating that prolonged exposure is needed for sustained adaptation.
Bock
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Institute for Space and Terrestrial Science, York University, North York, Ont., Canada.
Howard
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IP
Money
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Arnold
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KE
D000337:Aerospace Medicine; D001132:Arm; D006112:Gravitation; D006801:Humans; D008433:Mathematics; D009068:Movement; D011597:Psychomotor Performance