NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Effects of spaceflight on rhesus quadrupedal locomotion after return to 1GEffects of spaceflight on Rhesus quadrupedal locomotion after return to 1G. Locomotor performance, activation patterns of the soleus (Sol), medial gastrocnemius (MG), vastus lateralis (VL), and tibialis anterior (TA) and MG tendon force during quadrupedal stepping were studied in adult Rhesus before and after 14 days of either spaceflight (n = 2) or flight simulation at 1G (n = 3). Flight simulation involved duplication of the spaceflight conditions and experimental protocol in a 1G environment. Postflight, but not postsimulation, electromyographic (EMG) recordings revealed clonus-like activity in all muscles. Compared with preflight, the cycle period and burst durations of the primary extensors (Sol, MG, and VL) tended to decrease postflight. These decreases were associated with shorter steps. The flexor (TA) EMG burst duration postflight was similar to preflight, whereas the burst amplitude was elevated. Consequently, the Sol:TA and MG:TA EMG amplitude ratios were lower following flight, reflecting a "flexor bias." Together, these alterations in mean EMG amplitudes reflect differential adaptations in motor-unit recruitment patterns of flexors and extensors as well as fast and slow motor pools. Shorter cycle period and burst durations persisted throughout the 20-day postflight testing period, whereas mean EMG returned to preflight levels by 17 days postflight. Compared with presimulation, the simulation group showed slight increases in the cycle period and burst durations of all muscles. Mean EMG amplitude decreased in the Sol, increased in the MG and VL, and was unchanged in the TA. Thus adaptations observed postsimulation were different from those observed postflight, indicating that there was a response unique to the microgravity environment, i.e., the modulations in the nervous system controlling locomotion cannot merely be attributed to restriction of movement but appear to be the result of changes in the interpretation of load-related proprioceptive feedback to the nervous system. Peak MG tendon force amplitudes were approximately two times greater post- compared with preflight or presimulation. Adaptations in tendon force and EMG amplitude ratios indicate that the nervous system undergoes a reorganization of the recruitment patterns biased toward an increased recruitment of fast versus slow motor units and flexor versus extensor muscles. Combined, these data indicate that some details of the control of motor pools during locomotion are dependent on the persistence of Earth's gravitational environment.
Document ID
20040141964
Document Type
Reprint (Version printed in journal)
Authors
Recktenwald, M. R. (University of California Los Angeles, California 90095-1527, United States)
Hodgson, J. A.
Roy, R. R.
Riazanski, S.
McCall, G. E.
Kozlovskaya, I.
Washburn, D. A.
Fanton, J. W.
Edgerton, V. R.
Rumbaugh, D. M.
Date Acquired
August 22, 2013
Publication Date
May 1, 1999
Publication Information
Publication: Journal of neurophysiology
Volume: 81
Issue: 5
ISSN: 0022-3077
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
Bion 11 Project
NASA Discipline Musculoskeletal
Flight Experiment
Non-NASA Center
unmanned
short duration