Energy Systems Explained

By: Lauren Peterson, M.S., CSCS, FMS-level 1

SPARC Sports Performance Coordinator

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                                                                                                              (adapted from Verheijen, 1998)

Consider an elite, 400m runner (lets call him… Fred), who is competing in the upcoming Olympic trials to qualify for Rio. Fred’s typical pre-race breakfast consists of 3 whole eggs, 5 egg whites, 1 cup of oatmeal, 2 tablespoons of peanut butter, and 1 cup of blueberries. His body digests the food and stores the energy away in the form of ATP, glycogen, and other fuels.  Fast forward to the starting line, Fred’s body begins to anticipate the upcoming race by releasing hormones to ramp his energy systems and utilize these stored fuels. The gun fires and Fred explodes out of the blocks. In this initial drive phase, his muscles tear through the stored ATP at an immense rate, while at the same time, draw a small amount of energy from the breakdown of glucose through aerobic and anaerobic mechanisms. As he nears the 100m mark, his body is runs out of stored ATP, and starts to rely more on the other two energy sources. This shift towards aerobic metabolisms continues throughout the race in order to keep Fred’s muscles firing at top speed. Due to the training Fred has put in all year, his energy systems are able to keep up with the demands of the race, and he crosses the line in 44.77 sec, and qualifies for Rio!

As you can see, an adequate supply of energy is key to maintaining a high level of sports performance. One of the main goals of training periodization (manipulation of frequency, intensity, time, and type of exercise) is to optimize the body’s energy systems to meet the demands of competition. There are three major energy systems, Creatine Phosphate system (PCr), Glycolytic, and Aerobic/Oxidative. While the body draws from each energy system regardless of exercise intensity, the relative contribution of each energy system is dictated by the duration and intensity of activity.  We will review each energy system and how to manipulate them for optimize performance.

If you examine the graph above, it is obvious that the energy system capable of producing the most power is the Creatine Phosphate system (PCr). PCr is an anaerobic energy system and does not rely on oxygen to transfer glucose into ATP. The only drawback of this type of energy system is that cannot be maintained for very long. It is most highly involved in activities such as: short distance max effort sprints, max effort lifts, high jump, long jump, shot put, discus, etc.

The Glycolytic  (anaerobic) system is in between PCr and aerobic/oxydative systems. It can produce energy for slightly longer than PCr and is the one that leaves your muscles and lungs burning. The Glycolytic system produces lactate (can be converted in to lactic acid), and when the production of lactate is greater than the removal of lactate, the body switches over to using the aerobic energy system. Training the Glycolytic system, increases it’s efficiency of removing lactate from the blood.

The aerobic energy system is less powerful than PCr or Glycolytic but is long sustaining. It requires oxygen to transform glucose and fatty acids into fuel and allows athletes to perform for long periods of time. This system is most important for endurance athletes.

So how do we apply this to training? Remember, as the graph shows, the body draws from each energy system regardless of exercise intensity, but the contribution of each is dictated by duration and intensity of activity. Therefore, the duration and intensity of the sport will determine the greatest energy system focus in training. For example, majority of training for a marathon runner is focused on the aerobic energy system with secondary focus on Glycolytic and small focus on PCr. For a Shot Putter the greatest focus is on PCr with much less focus on Glycolytic and almost no focus on aerobic. Some sports are more mixed on their energy training focus, these sports include: 400m runners, soccer, basketball, football, and rugby.

So what is the take away?

  • Work with a coach who understand energy systems and how to balance them in your training.
  • Working all energy systems is important for health and performance but depending on your sport, there should be a greater focus on anaerobic or aerobic training. 一