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Skeletal muscle responses to unloading in humansThis study examined the effects of unloading on skeletal muscle structure. Method: Eight subjects walked on crutches for six weeks with a 110 cm elevated sole on the right shoe. This removed weight bearing by the left lower limb. Magnetic resonance imaging of both lower limbs and biopsies of the left m. vastus laterallis (VL) were used to study muscle structure. Results: Unloading decreased (P less than 0.05) muscle cross-sectional areas (CSA) of the knee extensors 16 percent. The knee flexors showed about 1/2 of this response (-7 percent, P less than 0.05). The three vasti muscles each showed decreases (P less than 0.05) of about 15 percent. M. rectus femoris did not change. Mean fiber CSA in VL decreased (P less than 0.05) 14 percent with type 2 and type 1 fibers showing reductions of 15 and 11 percent respectively. The ankle extensors showed a 20 percent decrease (P less than 0.05) in CSA. The reduction for the 'fast' m. gastrocnemius was 27 percent compared to the 18 percent decrease for the 'slow' soleus. Summary: The results suggest that decreases in muscle CSA are determined by the relative change in impact loading history because atrophy was (1) greater in extensor than flexor muscles, (2) at least as great in fast as compared to slow muscles or fibers, and (3) not dependent on single or multi-joint function. They also suggest that the atrophic responses to unloading reported for lower mammals are quantitatively but not qualitatively similar to those of humans.
Document ID
19950010328
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Dudley, G. (Bionetics Corp. Cocoa Beach, FL., United States)
Tesch, P. (NASA John F. Kennedy Space Center Cocoa Beach, FL, United States)
Hather, B. (NASA John F. Kennedy Space Center Cocoa Beach, FL, United States)
Adams, G. (NASA John F. Kennedy Space Center Cocoa Beach, FL, United States)
Buchanan, P. (NASA John F. Kennedy Space Center Cocoa Beach, FL, United States)
Date Acquired
September 6, 2013
Publication Date
May 14, 1992
Publication Information
Publication: Aerospace Medical Association, Aerospace Medical Association 63rd Annual Scientific Meeting Program
Subject Category
Aerospace Medicine
Accession Number
95N16743
Funding Number(s)
CONTRACT_GRANT: NAS10-11624
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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