Final answer:
Fast (white) muscle fibers, or Type-IIb fibers, have fewer mitochondria and myoglobin compared to other muscle fiber types. They are smaller in diameter and have low resistance.
Step-by-step explanation:
Fast (white) muscle fibers, categorized as Type-IIb fibers, are characterized by their anaerobic and glycolytic nature. These fibers exhibit fewer mitochondria and myoglobin content compared to other muscle fiber types, resulting in a paler appearance. The reduced oxidative capacity makes them well-suited for short bursts of intense, rapid activity. Fast muscles have a smaller diameter, contributing to their quick contraction and relaxation cycles. Due to their low resistance to fatigue, they are particularly involved in activities requiring explosive strength, such as sprinting or weightlifting. The distinct features of fast muscle fibers enable efficient performance in high-intensity, short-duration activities.