In general physical activity, also called motor activity, is "any bodily movement produced by skeletal muscles that requires energy expenditure."[1]
Exercise is "physical activity which is usually regular and done with the intention of improving or maintaining physical fitness or health."[2]
In physiology physical activity is "the physical activity of a human or an animal as a behavioral phenomenon."[3]
Promoting physical activity is difficult; a systematic review found "the most effective interventions were behavioral interventions instead of cognitive interventions, face-to-face delivery versus mediated interventions (e.g., via telephone or mail), and targeting individuals instead of communities."[4]
Simple interventions might help.[5]