Final answer:
Type II B muscle fibers are characterized by high fatigability due to their reliance on anaerobic metabolism, leading to quick fatigue during intense activity.
Step-by-step explanation:
The major limitation of type II B muscle fibers is high fatigability. Type II B fibers, also known as fast glycolytic or white muscle fibers, rely on anaerobic metabolism to produce energy, leading them to fatigue quickly. These fibers are adapted for quick bursts of power and have high contraction velocity, but they can only sustain activity for short periods before fatigue sets in. The quick energy comes at a cost: they use their large glycogen reserves quickly and accumulate byproducts such as lactic acid during intense activity. In contrast, type I fibers, or slow-twitch muscle fibers, are mainly responsible for aerobic activities and can sustain contractions for extended periods due to their high myoglobin content and abundant mitochondria.