muscle
• mice exhibit a switch from a slow- to fast-twitch skeletal muscle phenotype, with an elevation of fast-twitch skeletal muscle gene expression in gastrocnemius and soleus muscles, a decrease in the type I fibers and increase in type IIa fibers in the soleus muscle, and an increase in maximal (tetanic) contractile strength and decrease in half relaxation time in the soleus
• however, no changes in the overall oxidative capacity of mutant soleus or EDL muscles and hearts do not exhibit myofibril disarray
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