During high-intensity exercise, from where do muscles primarily get their energy?

• A. Fatty acid oxidation
• B. Anaerobic glycolysis (breakdown of glucose without oxygen)
• C. Oxidative phosphorylation in mitochondria
• D. Photosynthesis

Answer: (B)

Verified step by step guidance

1. Understand the context: During high-intensity exercise, the body requires energy quickly. This means the energy source must be rapidly accessible and not rely on slower processes like oxygen delivery or fat breakdown.
2. Review the energy pathways: Muscles can generate energy through three main pathways: (1) anaerobic glycolysis (breakdown of glucose without oxygen), (2) oxidative phosphorylation (a slower, oxygen-dependent process in mitochondria), and (3) fatty acid oxidation (a slower process that also requires oxygen).
3. Eliminate irrelevant options: Photosynthesis is a process used by plants to convert light energy into chemical energy and is not applicable to human muscle cells.
4. Focus on anaerobic glycolysis: During high-intensity exercise, oxygen delivery to muscles is limited, so the body relies on anaerobic glycolysis. This process breaks down glucose into pyruvate, producing ATP quickly but less efficiently, and results in the production of lactate.
5. Conclude: The primary energy source during high-intensity exercise is anaerobic glycolysis because it provides a rapid supply of ATP without requiring oxygen, unlike oxidative phosphorylation or fatty acid oxidation.