Which of the following describes Type I muscle fibers?

• A. They primarily use anaerobic metabolism.
• B. They are slow-twitch fibers with high endurance.
• C. They are responsible for quick, powerful movements.
• D. They are fast-twitch fibers with low endurance.

Answer: (B)

Verified step by step guidance

1. Understand the characteristics of Type I muscle fibers: These fibers are known as slow-twitch fibers, which means they contract slowly and are resistant to fatigue.
2. Recognize the metabolic process used by Type I muscle fibers: They primarily rely on aerobic metabolism, which is efficient for long-duration activities and uses oxygen to generate energy.
3. Identify the endurance level of Type I muscle fibers: Due to their reliance on aerobic metabolism, Type I fibers have high endurance and are suited for activities like marathon running or cycling.
4. Differentiate between Type I and Type II muscle fibers: Type II fibers are fast-twitch, responsible for quick, powerful movements, and primarily use anaerobic metabolism, which is less efficient for endurance.
5. Conclude that Type I muscle fibers are characterized by their slow contraction speed, high endurance, and reliance on aerobic metabolism, making them ideal for sustained activities.