Which statement best describes fast-twitch muscle fibers?

Which statement best describes fast-twitch muscle fibers?

• A. They contract slowly and generate high force
• B. They are resistant to fatigue
• C. They contract quickly but fatigue slowly
• D. They contract quickly and fatigue rapidly

Answer: (D)

Fast-twitch muscle fibers are built for quick, powerful actions. They contract rapidly, producing high force in a short time, but they fatigue rapidly because they rely mainly on anaerobic energy systems and have fewer mitochondria and capillaries to sustain activity. This combination makes them ideal for short, intense efforts like sprints or heavy lifts. So, the statement that describes them best is that they contract quickly and fatigue rapidly. (There are fast-twitch subtypes with different fatigue levels, but the general pattern is fast contraction with quicker fatigue.)

Fast-twitch muscle fibers are built for quick, powerful actions. They contract rapidly, producing high force in a short time, but they fatigue rapidly because they rely mainly on anaerobic energy systems and have fewer mitochondria and capillaries to sustain activity. This combination makes them ideal for short, intense efforts like sprints or heavy lifts. So, the statement that describes them best is that they contract quickly and fatigue rapidly. (There are fast-twitch subtypes with different fatigue levels, but the general pattern is fast contraction with quicker fatigue.)