If a marathon runner experiences sudden muscle failure at the 20-mile mark despite adequate hydration and glycogen stores, which consequence involving the neuromuscular junction is most likely?

💡 Explanation

Reduced acetylcholine release at the neuromuscular junction leads to muscle failure because it impairs the transmission of action potentials to muscle fibers, thus inhibiting muscle contraction. Therefore, diminished acetylcholine release is the key failure mode, rather than changes in receptor sensitivity or calcium handling within the muscle cell.

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