Which substrate pattern best describes fuel use in resting vs trained skeletal muscle during aerobic respiration?

Which substrate pattern best describes fuel use in resting vs trained skeletal muscle during aerobic respiration?

• A. Resting uses fats; trained uses only glucose.
• B. Resting uses glucose only; trained uses protein.
• C. Resting uses mostly fatty acids and glucose; trained muscles have increased mitochondrial density and oxidative capacity, allowing greater fat oxidation and glucose utilization efficiency.
• D. Resting uses mostly proteins; trained uses fats.

Answer: (C)