Research
Mixed
Soleus muscle is more susceptible to atrophy and fiber type shifting than the gastrocnemius during long-duration spaceflight, exhibiting a 15% volume loss and a 17% decrease in MHC I fibers.
Postural muscles like the soleus (calf) are highly sensitive to unloading. If you are immobilized or bedridden, expect significant loss of postural endurance and calf strength. Rehabilitation should prioritize specific loading of these slow-twitch dominant muscles.
GoodSupportsHIGH confidence
The soleus (-15 ± 2%) atrophied more (P < 0.05) than the gastrocnemius (-10 ± 2%) pre- to postflight... On average, the soleus had a 17% decrease (P < 0.05) in MHC I fibers.
Why this rating
Direct biopsy and MRI data on human subjects.
Source
Exercise in space: human skeletal muscle after 6 months aboard the International Space Station
Scott Trappe et al. · Journal of Applied Physiology · 2009
DOI 10.1152/japplphysiol.91578.2008
cohort · n=9Cited 445×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
More from this paper
- Current ISS exercise countermeasures (aerobic and resistance) are insufficient to prevent significant calf muscle atrophy, loss of force-generating capacity, and slow-to-fast fiber type transitions during 6-month spaceflight.Good
- Long-duration spaceflight induces a slow-to-fast myosin heavy chain (MHC) transition in both gastrocnemius and soleus muscles, characterized by a decrease in MHC I fibers and an increase in hybrid MHC I/IIa fibers.Good
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