Following prolonged detraining in elite strength/power athletes, which physical characteristic will show the largest reduction due to the removal of an anaerobic stimulus?

Following prolonged detraining in elite strength/power athletes, which physical characteristic will show the largest reduction due to the removal of an anaerobic stimulus?

• A. Total fat mass
• B. Fast-twitch fiber CSA
• C. Slow-twitch fiber CSA
• D. Total Type I muscle fiber content

Answer: (B)

The key idea is that removing the rapid, high-intensity stimuli that drive strength and power causes atrophy most in fast-twitch (Type II) fibers. In elite strength/power athletes, these fibers contribute most to big force and power outputs. When detraining occurs, the signaling that promotes muscle protein synthesis in these fibers wanes, leading to a decrease in their cross-sectional area. Fast-twitch fibers respond more dramatically to such disuse than slow-twitch fibers, which are more resistant to atrophy. The total content of Type I fibers doesn’t change quickly, and fat mass doesn’t typically decrease with detraining—in fact, it often increases due to lower energy expenditure. So the largest reduction among the options is the cross-sectional area of fast-twitch fibers.

The key idea is that removing the rapid, high-intensity stimuli that drive strength and power causes atrophy most in fast-twitch (Type II) fibers. In elite strength/power athletes, these fibers contribute most to big force and power outputs. When detraining occurs, the signaling that promotes muscle protein synthesis in these fibers wanes, leading to a decrease in their cross-sectional area. Fast-twitch fibers respond more dramatically to such disuse than slow-twitch fibers, which are more resistant to atrophy. The total content of Type I fibers doesn’t change quickly, and fat mass doesn’t typically decrease with detraining—in fact, it often increases due to lower energy expenditure. So the largest reduction among the options is the cross-sectional area of fast-twitch fibers.