The concept of dose is important in clinical medicine. In the pharmacological treatment of many conditions, physicians typically start with a dose of a drug believed to be the minimum effective dose. If the patient does not respond, this initial dose may then be titrated upward to a maximum dose, beyond which the adverse effects of the drug are unacceptable for treatment. Thus, all marketed drugs require data on their efficacy and safety.
Physical activity, while not a drug, can behave like one—it causes many physiological changes in the body (often beneficial for health),1 helps prevent the development of many chronic diseases,2 and is a useful adjunct to drug treatment for many diseases, including cardiovascular disease, cancer, and diabetes.3,4 Health care professionals, including physicians, are encouraged to prescribe physical activity for health.3,4 It is plausible that there is a minimum dose of physical activity for health benefits, that these benefits increase with increasing dose, and that beyond a certain dose, adverse effects (eg, musculoskeletal injuries,5 sudden death6) outweigh benefits.