Jake is a sprinter on the track team. When he is sprinting, how does his body get the fuel it needs?

Answer 1

Muscles use both anaerobic and aerobic metabolic pathways to fuel physical activity. The intensity and duration of the activity and the availability of oxygen in the muscles determine the relative contribution of each pathway. Sprinting relies heavily on anaerobic pathways that deliver large amounts of ATP quickly.
The anaerobic pathways, which can generate ATP without relying on oxygen, include the ATP creatine phosphate (ATP-CP) pathway and glycolysis. The ATP-CP pathway can be thought of as an immediate energy system, while glycolysis is considered a short-term energy system. Anaerobic metabolic pathways are relatively simple compared to aerobic pathways, so ATP production is very fast. However, anaerobic pathways cannot maintain a high rate of ATP production for very long. This is why the body can rely on anaerobic metabolism only for brief periods of time.
At the onset of sprinting, Jake relies on both aerobic and anaerobic pathways to some extent. As exercise continues, there is a greater demand on glycolysis—which also can be thought of as a short-term energy system—to generate ATP. However, if physical activity is to continue, muscles must increase their use of oxygen-requiring (aerobic) pathways (such as the citric acid cycle) for ATP production. These pathways can be thought of as long-term energy systems.