Which statement accurately describes Type II skeletal muscle fibers?

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Multiple Choice

Which statement accurately describes Type II skeletal muscle fibers?

Type II skeletal muscle fibers are fast-twitch and glycolytic, designed for quick, powerful contractions. They contract rapidly and rely on anaerobic glycolysis to supply ATP, supporting short bursts of high-intensity activity like sprinting. Because their energy comes mainly from glycolysis, they have fewer mitochondria and less myoglobin than slow-twitch fibers, so they fatigue more quickly. The other statements don’t fit: slow-twitch oxidative fibers are, as the name implies, slow and endurance-oriented; non-fatigable describes endurance-type fibers that resist fatigue; and relying exclusively on aerobic metabolism would describe those fibers with high oxidative capacity, not the fast glycolytic Type II. In short, the defining feature is fast, glycolytic energy production for rapid contractions.

Type II skeletal muscle fibers are fast-twitch and glycolytic, designed for quick, powerful contractions. They contract rapidly and rely on anaerobic glycolysis to supply ATP, supporting short bursts of high-intensity activity like sprinting. Because their energy comes mainly from glycolysis, they have fewer mitochondria and less myoglobin than slow-twitch fibers, so they fatigue more quickly. The other statements don’t fit: slow-twitch oxidative fibers are, as the name implies, slow and endurance-oriented; non-fatigable describes endurance-type fibers that resist fatigue; and relying exclusively on aerobic metabolism would describe those fibers with high oxidative capacity, not the fast glycolytic Type II. In short, the defining feature is fast, glycolytic energy production for rapid contractions.

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