What can lead to muscle atrophy?

Muscle atrophy occurs when there is a decrease in the size or mass of muscle fibers, typically resulting from a lack of use or stimulation of those muscles. When muscles are not engaged in regular activity or load-bearing exercises, the body begins to break down the muscle tissue to conserve energy and resources, leading to a reduction in muscle mass. This phenomenon can be seen in individuals who are sedentary, bedridden, or recovering from injuries that limit movement.

In contrast, regular strength training and consistent aerobic exercises actively stimulate the muscles, promoting their growth and maintenance. Increased protein intake is beneficial for muscle repair and growth but will not prevent atrophy if the muscles are not being used. Therefore, the choice that directly aligns with the cause of muscle atrophy is the lack of use or stimulation, as it emphasizes the necessity of activity to maintain muscle health.