Muscle atrophy occurs when there's _____.

• A. An excess of exercise
• B. A build up of cardiac tissue
• C. An excess of insulin
• D. A breakdown of muscle tissue

Answer: (D)

Muscle atrophy is the wasting or shrinking of muscle tissue that occurs when the body breaks down muscle proteins faster than they’re rebuilt. This often happens with disuse or immobilization, aging, or chronic illness, so the muscles lose their size and strength as fibers become smaller. That breakdown of muscle tissue is what leads to atrophy. In contrast, excessive exercise typically causes the opposite effect (hypertrophy), a buildup of heart tissue isn’t about skeletal muscle, and insulin mostly promotes growth rather than wasting.