Which of the following best describes slow-twitch muscle fibers?

• A. They rely primarily on anaerobic metabolism for energy.
• B. They have low myoglobin content and few mitochondria.
• C. They contract rapidly and generate powerful, short bursts of strength.
• D. They are resistant to fatigue and specialized for endurance activities.

Answer: (D)

Verified step by step guidance

1. Understand the characteristics of slow-twitch muscle fibers: These fibers are specialized for endurance activities and are resistant to fatigue. They rely primarily on aerobic metabolism, which requires oxygen, to generate energy efficiently over long periods.
2. Recognize the role of myoglobin in slow-twitch muscle fibers: Myoglobin is a protein that stores oxygen in muscle cells. Slow-twitch fibers have high myoglobin content, which supports their reliance on aerobic metabolism.
3. Identify the presence of mitochondria in slow-twitch muscle fibers: Mitochondria are the organelles responsible for aerobic energy production. Slow-twitch fibers contain numerous mitochondria to sustain prolonged activity.
4. Contrast slow-twitch fibers with fast-twitch fibers: Fast-twitch fibers are designed for short bursts of strength and rely on anaerobic metabolism, which does not require oxygen. They have lower myoglobin content and fewer mitochondria compared to slow-twitch fibers.
5. Conclude that slow-twitch muscle fibers are resistant to fatigue and specialized for endurance activities, making them ideal for sustained, low-intensity exercises like long-distance running or cycling.