Isometric force production during changed-Gz episodes of parabolic flight.
Changes of the normal gravitational acceleration are known to affect sensorimotor performance. For example, subjects exposed to three times the normal terrestrial acceleration (+3 Gz) in a centrifuge will produce exaggerated isometric force. The present study compares the effects of high-Gz to that of micro-Gz on isometric force production. Twelve right-handed human subjects were tested during the microgravity (micro-Gz), high gravity (high-Gz) and normal gravity (normal-Gz) episodes of parabolic flight. Holding an isometric joystick in their right hand, they produced forces of 5, 15, or 25 N in different directions, according to visually prescribed vectors. In some parabolas, 70 Hz vibration was applied to the flexor- and extensor-side of the wrist, in order to reduce spinal segmental activity. If compared to normal-Gz, produced forces were higher in high-Gz, and still higher in micro-Gz. Vibration reduced the magnitude of produced forces independent of the Gz-level. We confirm that isometric force increases in high-Gz, and document that it increases in micro-Gz as well. This increase is probably not related to degraded segmental excitability and proprioception, since it was not modified by vibration and manifests before proprioception becomes effective.
Mierau
Andreas
A
Institute of Physiology and Anatomy, German Sport University, Cologne, 50933, Germany. mierau@dshs-koeln.de
Girgenrath
Michaela
M
Bock
Otmar
O
D000054:Acceleration; D000328:Adult; D000337:Aerospace Medicine; D002498:Centrifugation; D005260:Female; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D018471:Hypergravity; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D011434:Proprioception / Q000502:physiology; D012018:Reflex / Q000502:physiology; D018561:Space Simulation; D014732:Vibration; D014893:Weightlessness; D014953:Wrist