Which statement is true of detraining following endurance training?

• A. It can impair submaximal endurance performance
• B. It always improves sprint speed
• C. It has no effect on VO2 max
• D. It immediately increases muscle mass

Answer: (A)

Detraining after endurance training leads to a regression of aerobic adaptations, which can impair submaximal endurance performance. Endurance training builds mitochondrial density, oxidative enzyme activity, and capillary networks that optimize oxygen use and energy production during prolonged efforts. When training stops, these adaptations fade, reducing VO2 max and the body’s efficiency at submaximal workloads. That’s why submaximal endurance performance can decline. Sprint speed isn’t guaranteed to improve with detraining and may stay the same or decrease, depending on whether sprint-specific abilities are maintained. VO2 max typically falls with detraining, not stays the same, and muscle mass does not increase—in fact, disuse can lead to muscle loss.