Basic concept Physical activity. any bodily movement produced by the contraction of skeletal muscle that increases energy expenditure above a basal level Exercise. A subcategory of physical activity that is planned. structured repetitive and purposive in the sense that the improvement or maintenance of one or more components of physical fitness is the objectivePhysical activity. Any bodily movement produced by the contraction of skeletal muscle that increases energy expenditure above a basal level. Exercise. A subcategory of physical activity that is planned, structured, repetitive, and purposive in the sense that the improvement or maintenance of one or more components of physical fitness is the objective. Basic concept