If a long-distance runner on a thiamine-deficient diet experiences muscle weakness and fatigue, which metabolic consequence most directly impairs their performance?

💡 Explanation

Beriberi, caused by thiamine (vitamin B1) deficiency, inhibits pyruvate dehydrogenase. This enzyme is vital for converting pyruvate to acetyl-CoA for the Krebs cycle; because thiamine is a cofactor, its absence impairs ATP production from glucose, therefore muscle cells experience reduced energy output, rather than issues with iron, calcium or glycogen.

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