Which description best characterizes white muscle?

• A. White muscle is mostly fast fibers, pale, limited blood supply, fast contractions, fatigues rapidly.
• B. White muscle is mostly slow fibers, dark.
• C. White muscle is found only in the heart.
• D. White muscle has a rich blood supply.

Answer: (A)

White muscle describes skeletal fibers that are fast-twitch and glycolytic. These fibers contract quickly to produce short, powerful bursts, but they fatigue rapidly because they rely mainly on anaerobic metabolism. The pale color comes from low myoglobin content, and the limited blood supply means fewer capillaries and less oxygen delivery. This combination makes white muscle well-suited to rapid, explosive actions rather than endurance. In contrast, red muscle is rich in myoglobin, has more capillaries and mitochondria, and supports endurance with slower, fatigue-resistant contractions. Also, heart muscle is cardiac muscle, not white skeletal muscle, which is why the idea of white muscle being found only in the heart doesn’t fit.