What is the effect of fast-twitch glycolytic muscle fibers during high-intensity exercise?

Fast-twitch glycolytic muscle fibers, also known as type IIb fibers, are specialized for short bursts of high-intensity activity. During high-intensity exercise, these fibers are primarily utilized because they can generate force quickly and powerfully. However, they primarily rely on anaerobic metabolism for energy, which leads to the rapid accumulation of lactate and other metabolic byproducts. This anaerobic process does not support prolonged activity; instead, it results in a quicker onset of fatigue compared to other fiber types.

As a result, the effect of these fibers during high-intensity exercise is characterized by rapid fatigue due to their reliance on anaerobic energy production and the limited ability to sustain such high levels of output for extended periods. This is markedly different from the characteristics of endurance fibers, which enable longer activity durations and are more resistant to fatigue.