Like all types of physical activity, strength training and aerobic training use calories. Strength training is unique, though, in that it can decrease body fat and increase muscle mass, thereby improving body composition and enhancing appearance and performance. Muscle tissue requires more calories to function than fat and as a result, kids with more muscle are more efficient at using calories. Aerobic training is also important since it can produce a sustained and significant use of calories and improves overall health and energy (both physically and mentally).