Shuttle-Mir and NASA-Mir Reduced muscle mass, strength and performance in space

figure 6-9. percent change in selected muscle groups during short (8 d; n = 8) , long (115 d; n = 3) spaceflight (mir 18) compared long-duration bed rest (119 d). data references , shuttle/mir final report.

there correlation between long-duration bed rest , spaceflight of similar duration except losses in muscles less bed rest. reflects use of these muscles during bed rest adjust body position , reduce potential vascular compression , tissue injury. during spaceflight muscles apparently less used because not have support upright body against earth gravity , not used great force make positional adjustments of body during recumbency of bed rest.