Physical activity is an inclusive term that refers to any expenditure of energy brought about by bodily movement via the skeletal muscles; as such, it includes the complete spectrum of activity from very low resting levels to maximal exertion. exercise is a component of physical activity. the distinguishing characteristic of exercise is that it is a structured activity specifically planned to develop and maintain physical fitness. "exercise" britannica school. encyclopaedia britannica, inc., 2013. web. 21 oct. 2013. how is the word distinguishing used in this excerpt? to indicate that exercise is just one specific type of physical activity to show that exercise needs to be structured to maintain fitness to identify the components of maintaining and planning activity to describe the types of exercise used to develop physical fitness