Contrast the metabolic profiles of slow-twitch and fast-twitch muscle fibers and the resulting performance implications.

• A. Slow-twitch rely on glycolysis for rapid power.
• B. Fast-twitch rely on oxidative metabolism for endurance.
• C. Slow-twitch rely on oxidative metabolism for endurance and fatigue resistance.
• D. Fast-twitch rely on ATP storage.

Answer: (C)

Slow-twitch fibers are built for endurance. They rely on oxidative metabolism, using many mitochondria, high myoglobin content, and a dense network of capillaries to produce ATP aerobically. This setup supports sustained, low-to-moderate intensity contractions and makes these fibers resistant to fatigue, which is why they dominate activities like long-distance running and maintaining posture. In contrast, fast-twitch fibers are geared for quick, powerful movements and rely more on glycolysis and phosphagen systems to generate ATP rapidly, which leads to quicker fatigue. The statement that slow-twitch fibers rely on oxidative metabolism for endurance and fatigue resistance accurately reflects their metabolic profile and how it translates to performance.