Exercises that involve the release of catabolic hormones such as norepinephrine -- or adrenalin -- and cortisol will result in little to no accumulation of muscle mass but will burn lots of calories in the process of enhancing cardiovascular fitness. Thus catabolic exercise is essentially the same as aerobic exercise, and includes moderate-intensity workouts that can be sustained for as long as several hours; running, cycling, swimming and cross-country skiing are archetypcal examples. Because the muscle loading seen in resistance training is not present, anabolic hormones are not released in significant enough amounts to compete with their catabolic counterparts, and thus a tendency toward loss of body mass predominates.