Muscle atrophy is when muscles waste away. The main reason for muscle wasting is a lack of physical activity. This can happen when a disease or injury makes it difficult or impossible for you to move an arm or leg.

Causes of Muscle Atrophy
Unused muscles can waste away if you are not active. However, this takes time. Even after it begins, this type of atrophy can often be reversed with exercise and improved nutrition.

Muscle atrophy can also happen if you are bedridden or unable to move certain body parts due to a medical condition. Astronauts are subject to some muscle atrophy after a few days of weightlessness.

Other causes for muscle atrophy include:

• lack of physical activity (for any reason)
• aging
• alcohol-associated myopathy (pain and weakness in muscles due to excessive drinking over long periods of time)
• burns
• injuries and broken bones
• malnutrition
• spinal cord injuries
• stroke
• long-term corticosteroid therapy