Which statement best describes mitochondrial density and metabolism in slow-twitch vs fast-twitch muscle fibers?

• A. Slow-twitch fibers have low mitochondrial density and rely on glycolysis; fast-twitch have higher density and oxidative.
• B. Slow-twitch fibers have high mitochondrial density and oxidative capacity, while fast-twitch fibers have lower mitochondrial density and rely more on glycolysis.
• C. Both types have equal mitochondrial density.
• D. Mitochondria are not present in fast-twitch fibers.

Answer: (B)