Define the term "muscle atrophy."

Muscle atrophy refers to the decrease in muscle mass and strength that occurs when muscles are not used regularly or are affected by a disease. This condition typically arises from prolonged inactivity, such as bed rest or immobilization, as well as from certain medical conditions that may prevent normal muscle function or stimulate muscle breakdown.

When muscles are not regularly exercised, the body begins to break down muscle tissue for energy, which leads to a reduction in muscle size and strength. This can significantly impact overall physical performance and mobility. In contrast, the other terms describe different processes: an increase in muscle mass and strength occurs with regular exercise and training, while overdeveloped muscles and post-exercise muscle growth focus on scenarios of enhanced muscle performance rather than the degradation represented by atrophy.

Understanding muscle atrophy is essential for developing effective rehabilitation and exercise programs that aim to prevent or reverse this condition.