Which term describes the muscle fibers that contract rapidly but fatigue quickly?

The correct term for muscle fibers that contract rapidly but fatigue quickly is Type II fibers. These fibers are also known as fast-twitch fibers. They are specifically designed for explosive strength and short bursts of activity, making them essential for high-intensity training and activities like sprinting or heavy lifting. Type II fibers rely primarily on anaerobic metabolism, allowing them to produce energy quickly but leading to the accumulation of fatigue-producing substances, which is why they tire out rapidly.

In contrast, Type I fibers, or slow-twitch fibers, are more durable and better suited for endurance activities. They can sustain prolonged activities because they utilize aerobic metabolism, which is more efficient for long-duration exercise. Oxidative fibers, which are also associated with endurance, share characteristics with Type I fibers and are more resistant to fatigue. Therefore, when discussing rapid contraction coupled with quick fatigue, Type II fibers are clearly the appropriate descriptor.