Document Detail


Effects of spaceflight on rhesus quadrupedal locomotion after return to 1G.
MedLine Citation:
PMID:  10322080     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Effects 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.
Authors:
M R Recktenwald; J A Hodgson; R R Roy; S Riazanski; G E McCall; I Kozlovskaya; D A Washburn; J W Fanton; V R Edgerton
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Journal of neurophysiology     Volume:  81     ISSN:  0022-3077     ISO Abbreviation:  J. Neurophysiol.     Publication Date:  1999 May 
Date Detail:
Created Date:  1999-06-14     Completed Date:  1999-06-14     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0375404     Medline TA:  J Neurophysiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  2451-63     Citation Subset:  IM; S    
Affiliation:
Department of Physiological Science, University of California, Los Angeles, California 90095-1527, USA.
Space Flight Mission:
Bion 11 Project; Flight Experiment; short duration; unmanned
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MeSH Terms
Descriptor/Qualifier:
Adaptation, Psychological
Animals
Behavior, Animal / physiology
Electromyography
Gravitation*
Macaca mulatta / physiology*
Male
Motor Activity / physiology*
Muscle, Skeletal / physiology
Recruitment, Neurophysiological
Space Flight*
Tarsus, Animal / physiology
Tendons / physiology
Investigator
Investigator/Affiliation:
D M Rumbaugh / GA St U, Atlanta; V R Edgerton / U CA, Los Angeles

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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