Which muscle fiber type is known for fatiguing rapidly?

The muscle fiber type known for fatiguing rapidly is Type IIb fibers, which are also referred to as fast glycolytic fibers. These fibers are powerful and can generate a large amount of force quickly, making them well-suited for short bursts of high-intensity activities like sprinting or heavy lifting. However, they rely primarily on anaerobic metabolism for energy, which is less efficient than aerobic metabolism and leads to the accumulation of lactic acid. This accumulation is one of the main reasons they fatigue quickly.

In contrast, Type I fibers, or slow oxidative fibers, are designed for endurance activities. They are more resistant to fatigue because they utilize aerobic metabolism, making them ideal for prolonged activities like long-distance running. Type IIa fibers, also known as fast oxidative fibers, fall between the two extremes; they can sustain activity longer than Type IIb fibers but still fatigue faster than Type I fibers.