Which muscle fibers are subject to adaptation?

• A. Those subjected to resistance work
• B. All fibers equally
• C. Only slow-twitch fibers
• D. Only fast-twitch oxidative fibers

Answer: (A)

Adaptation happens where the muscle is actually loaded. When you push against resistance, the fibers that are recruited and stressed by that work receive the signals that drive change—growth, strength, or shifts in metabolic capacity. If a fiber isn’t recruited by the task, it doesn’t get the same stimulus and doesn’t adapt as much. So the fibers that experience the resistance are the ones most likely to adapt.

That’s why the best choice emphasizes the relationship between loading and adaptation: only the fibers subjected to resistance work undergo meaningful changes. The other options imply universal or exclusive adaptation to specific fiber types, which isn’t accurate since adaptation depends on the stimulus and recruitment pattern, not a fixed rule about a single fiber type.