Physical activity after cancer: physiologic outcomes.

Physical activity has many and varied effects on the human body. The physiologic effects of physical activity and exercise in persons with cancer have been largely unstudied. Cancer patients as a group are at risk for diseases and conditions related to lack of physical activity. In persons with cancer, exercise has been shown to improve fitness and physical functioning, reduce fatigue, and modestly decrease weight and body fat. The effects of physical activity on prognosis, however, are unknown. In persons without cancer, exercise has beneficial effects on the cardiovascular and endocrine systems, reducing risk of cardiovascular disease, cerebrovascular disease, and diabetes. Increased physical activity reduces risk for several common cancers, which is relevant to cancer survivors who are at increased risk for new primary cancers. Additional benefits of physical activity include improvements in fitness, muscular-skeletal problems including arthritis symptoms, immune system function, cognition and sleep. Risks of increased physical activity in cancer patients and survivors have not been defined, but could be expected to include musculo-skeletal injuries, and a small increased risk in sudden death with vigorous exercise and serious accidents with some sports. The effect of physical activity on survival from cancer is unknown, but physical activity might improve prognosis through beneficial effect on cancer biomarkers and energy balance, as well as decreasing risk for cardiovascular disease, an important cause of death for many cancer survivors. The long-term benefits and risks of physical activity in cancer patients and survivors are unknown. Nevertheless, increasing physical activity is probably beneficial and safe in the majority of cancer survivors.