During serious exercise training and competition, an athlete is aware of the proportion of stress on the three energy release systems of the human body: ATP-PC (Phosphagen) System, aerobic system and anaerobic (Lactic Acid) System. Some sports require activity or team position roles that require a variety and range of force and energy outputs. The importance of management of intensity during competition is that optimal energy output is available at the right time during the competition. While pushing beyond fatigue is admirable, and hustling all of the time is admirable, and some performances require 110% throughout the whole time period of performance, the magic in sports performance often involves a combination of pushing beyond the limits, but also in finding the time for recovery whenever possible. Even a distance runner can change gait and stride temporarily to utilize different muscles or different parts of muscles for a period of time during a distance race.
For optimal performance it is also important that an athlete trains specifically to push and adapt each system so that it is optimally available for competition.
The three energy systems are actually biochemical pathways that work in series and in parallel during performance. For example in a series of activity you could start with a sprint and end with a jog.
ATP-PC System (Phosphogen System) — energy released is managed for only very short durations of up to 10 seconds and then the system fails to provide maximum output. The ATP-PC system uses stored ATP (adenosine tri phosphate and PC (phosphocreatine), not oxygen. Lactic acid production is not part of this system, which is defined to be alactic anaerobic. For example a 100 meter sprint performance uses the energy output of the ATP-PC System.
Anaerobic System (Lactic Acid System or Glycolytic System) — energy released is managed for action lasting less than 2 minutes. The energy system uses alternate biochemical pathways when not enough oxygen is available to meet high intensity activity. An example of an activity of the intensity and duration with energy output from the Anaerobic System is a 400 meter sprint and then the maximum energy output fails — the pace slows down and the athlete must use some combination of the aerobic system to continue.
Aerobic System — energy released is met by the metabolism of available oxygen and nutritional fuel. Initially the body’s circulatory system is not prepared to deliver enough oxygen for most increased levels of activity, but by five minutes of exercise, the Aerobic System is the capable system. An example of steady state Aerobic System energy output is a long distance or marathon run.
If you looking for the topic of getting energy by eating proper food choices, see ‘Fuel States.’