ACE Personal Trainer Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

Type 2 muscle fibers, commonly referred to as fast-twitch fibers, are characterized by their low oxidative capacity and high glycolytic capacity. This means that they rely primarily on anaerobic metabolism to generate energy, which allows them to produce quick bursts of power and strength. These fibers are particularly effective for short-duration, high-intensity activities, such as sprinting or heavy lifting, where speed and force are required over endurance.

In contrast, the other characteristics mentioned do not align with the attributes of Type 2 fibers. The high oxidative capacity associated with endurance is a characteristic of Type 1 (slow-twitch) fibers, which are designed for sustained activity and utilize aerobic metabolism. Slow twitch performance again pertains to Type 1 fibers, which support longer-duration efforts. Similarly, efficiency in aerobic activities is not typical of Type 2 fibers, as their metabolic processes are not aimed at long-lasting aerobic performance but rather at generating rapid strength and speed. Thus, B accurately captures the defining traits of Type 2 muscle fibers.