Sports-related energy systems All three energy systems contribute, from very brief, intensive exercise to extremely modest, sustained activity. However, one or two will generally take the lead. For example, during a sprint, anaerobic metabolism dominates, which is based on glycolysis (see chapter: Glycolysis). As you become more trained and able to maintain proper form over long distances, your aerobic system becomes more important to supply oxygen to muscles and clear metabolic byproducts from the body. The main difference between the three systems is how they are maintained and recovered after use. Aerobic exercise can be any activity that uses large muscle groups, such as walking, jogging, swimming, basketball, etc., and requires moderate levels of exertion for several minutes at a time. The main goal here is to get out of the habit of thinking about exercise as something that depletes your energy level, because it doesn't. Exercise is energy consuming, but so is sitting at a desk all day. If you want to lose weight, you need to eat less and move more. Exercise is part of a healthy lifestyle, not a replacement for it. Anaerobic exercise is defined as activity that requires quick bursts of energy, such as running up stairs or jumping off objects.