As adults age and experience reduced mobility, which mechanism most directly explains the increased risk of sarcopenia in type II muscle fibers?

💡 Explanation

Sarcopenia arises from an imbalance between protein synthesis and degradation. Reduced mobility decreases muscle protein synthesis signaling, especially in fast-twitch type II fibers, because of inactivity-induced metabolic down-regulation. Therefore, protein breakdown exceeds synthesis, rather than increases in activation pathways or satellite cell proliferation.

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