“…Mechanical unloading or space travel causes muscle atrophy and a decline in peak force and power, with slow‐twitch muscle fibers becoming much weaker than fast‐twitch ones (Diffee, Caiozzo, Herrick, & Baldwin, ; Gao, Arfat, Wang, & Goswami, ; Leterme & Falempin, ; Williams, Kuipers, Mukai, & Thirsk, ). Ultrastructural changes constitute an important parameter to judge the degree of muscle atrophy or damage (Diffee et al, ; Volodina & Pozdnyakov, ). These include loss of nuclei, myofibrils, and sarcotubules, such as in the anterior tibial and soleus (SOL) muscles of hindlimb immobilized rats (Appell, ; Boonyarom & Inui, ; Fitts, Riley, & Widrick, ; Kim, Kwon, & Kim, ).…”