A marathon runner experiences muscle cramping and a burning sensation near the end of the race. What explains why increased intensity leads to this localized muscular pain?

💡 Explanation

Intense exercise leads to anaerobic metabolism and lactate production. This results in lactic acid accumulation, which lowers the intracellular pH in muscle tissue, causing a burning sensation because sensory nerve endings are stimulated by the acidity; therefore, the pain arises due to pH change rather than glycogen, creatine or oxygen changes.

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