Figure 1.

Physical activity produces primary and tertiary preventive health benefits for chronic diseases. Left panel. Physical inactivity is an actual initiating cause of a chronic disease/condition. Restoration of physical activity (primary prevention) removes the actual cause (physical inactivity) that produced the health deficiency. Right panel. Physical inactivity is not the cause of lung cancer. Smoking is an actual cause of lung cancer. Addition of aerobic exercise training compensates (tertiary prevention) for loss of lung function after surgical removal of a portion of lung by strengthening respiratory skeletal muscles for remaining lung (179). Exercise does not cure lung cancer.