Disuse atrophy—also known as muscle wasting—is characterized by muscle shrinkage and weakness due to inactivity. While it may begin as a mostly cosmetic issue, it can develop into a serious health problem over time. This condition can result from extended periods of immobility (e.g., while a certain body part is in a cast) or from a significant reduction of normal activity (e.g., being in a wheelchair and not being able to walk). In addition to limiting mobility, disuse atrophy can lead to heart problems as the muscle of the heart breaks down due to lack of exercise. Symptoms include weak and flabby muscle, difficulty performing certain tasks or activities, inability to hold correct posture, pain with movement, and stiffness and limited range of motion. Most people can reverse the effects of disuse atrophy by committing to an appropriate exercise regimen to stimulate muscle function and strengthening. Physical therapists can develop exercise programs tailored to a particular patient’s needs and abilities. In cases involving severe injury or debilitation, the clinical expertise of a qualified therapist is of the utmost importance as it is crucial that the patient engage in a program that will not put excessive stress on the heart and damaged muscles.