ANATOMY

Detailed explanation-1: -Fast oxidative (also called fast twitch or Type IIa) fibers have relatively fast contractions and primarily use aerobic respiration to generate ATP.

Detailed explanation-2: -Type IIx fibers, or fast glycolytic fibers, possess the fastest twitch speeds but are highly fatigable [1].

Detailed explanation-3: -Type IIA fibers have high myosin ATPase activity (pH 9.4), are fast twitch, have high oxidative and glycolytic capacity, and are relatively resistant to fatigue. Type IIB fibers have high myosin ATPase activity (pH 9.4), are fast twitch, have low oxidative and high glycolytic capacity, and fatigue rapidly.

Detailed explanation-4: -Fast-twitch fibers, particularly type IIx, tend to have higher concentrations of glycogen and creatine phosphate as well as higher activities of enzymes associated with glycogenolysis and glycolysis (Table 15-1).

Detailed explanation-5: -Fast-twitch muscles are a large proportion of the small muscles in hands and eyes for rapid movement. There are two subcategories of fast-twitch muscle fibers: Type IIA and Type IIB or Type IIX.