EFFECTS OF PHYSICAL-ACTIVITY AND EXERCISE ON EXPERIMENTALLY-INDUCED MAMMARY CARCINOGENESIS

Physical activity is defined as skeletal muscle contraction resulting in a quantifiable expenditure of energy, whereas exercise is a specifi c type of physical activity in which planned, structured, and repetiti ve bodily movement is done to improve or maintain one or more componen ts of physical fitness. The focus of laboratory studies of the physica l activity-breast cancer hypothesis has been on evaluating how various types of physical activity including exercise affect the process of m ammary carcinogenesis. A key objective has been the evaluation of the characteristics of physical activity, i.e. intensity, duration, and fr equency, required to confer protection against experimentally-induced breast cancer. The results of those studies indicate that exercise rat her than physical activity can exert a greater inhibitory effect again st experimentally-induced breast cancer, and that the duration of exer cise may not be as important as its intensity. This finding differs fr om evidence that other health benefits attributed to physical activity are proportional to the total amount of activity rather than the mann er in which it is obtained. In this review criteria are defined for ca tegorizing laboratory studies into those that investigated the effects of physical activity versus exercise on experimentally-induced mammar y carcinogenesis, and the Literature is reinterpreted in this context.