Which muscle fibers contract slowly and utilize low aerobic capacity?

• A. Fast-Twitch Fiber
• B. Slow-Twitch Fiber
• C. Static Fiber
• D. Elastic Fiber

Answer: (B)

The correct answer is Slow-Twitch Fiber. Slow-twitch muscle fibers, also known as Type I fibers, are characterized by their ability to contract at a slower rate compared to fast-twitch fibers. These fibers are highly efficient in using oxygen to generate energy through aerobic metabolism, which makes them particularly suited for prolonged, endurance activities. They have a high concentration of mitochondria, myoglobin, and blood supply, which contributes to their greater aerobic capacity.

In contrast, fast-twitch fibers (Type II) are designed for quick bursts of activity and rely more on anaerobic metabolism, making them less efficient for sustained efforts but ideal for high-intensity tasks. Static fibers and elastic fibers are not standard terms used to describe muscle fiber types associated with contraction speed or aerobic capacity. Static contractions refer to isometric exercises where the muscle exerts force without changing length, while elastic fibers are typically associated with connective tissues rather than muscle contraction.