During detraining, which change occurs in muscle oxygen processing?

• A. Muscles Become More Efficient At Processing Oxygen
• B. Muscles Process Oxygen Less Efficiently
• C. Muscles' Ability To Process Oxygen Remains Unchanged
• D. Muscles Require More Oxygen But Get It More Easily

Answer: (B)

When training stops, the muscles’ ability to use oxygen declines. Detraining reduces the mitochondria and oxidative enzymes in muscle fibers and can shorten capillary networks, all of which lower the muscle’s oxidative capacity. That means, for the same level of work, the muscle extracts and utilizes oxygen less efficiently, so oxygen processing becomes less efficient. As a result, the body relies more on anaerobic energy pathways and endurance performance tends to suffer. The other ideas—getting more efficient oxygen processing, no change, or oxygen being easier to obtain—don’t match what happens when conditioning is reduced.