What are the "Energy Systems" and how to train them - Part 2: the Anaerobic System

Today we are going to continue our discussion of the energy systems and how to train them. In the last post I discussed the ATP-PCr system, and in this post we will look at the Anaerobic (aka the Glycolytic) system.

Like the ATP-PCr system, the anaerobic is meant for high intensity exercise. The anaerobic system is able to maintain a high output of energy for longer than the ATP-PCr, however the power is significantly less than the ATP-PCr system. No matter which system we discuss, the muscle can ultimately only use one form of energy, and that is ATP. However, as I described in the last post, we don't carry enough ATP molecules to maintain vigorous exercise. Instead, we need to rely on alternative methods of generating ATP. The Anaerobic system uses stored Glucose and converts it into ATP to be used by the muscle (which explains why it is also referred to as the glycolytic system).

The process involves breaking down glucose (via glycolytic enzymes which are also present in the muscle cells, but realtively inactive when the anaerobic system is at rest). Glucose is the most basic for of carbohydrate and can be converted into energy (i.e. ATP) very quickly, though not very efficiently. In order to convert glucose (or the more complex glycogen) into ATP, the glucose molecule must undergo up to 12 enzymatic reactions. In other words, they need to be put through a bunch of processing steps before we can use it. These steps require the input of a molecule of ATP and have a net gain of 3 ATP for every molecule of glycogen that we break down. Despite these inefficiencies, the ATP-PCr and the Anaerobic energy system together allow the muscle to generate considerable amounts of force, very quickly.

In all-out bouts of exercise (think a spring at 100%) the demands placed on the anaerobic energy system are extremely high, in comparison to demands placed on the other energy systems. Anaerobic glycolysis (i.e. the breakdown of glycogen or glucose) also lead to the accumulation of lactic acid. Exercising at a high intensity, the anaerobic system will be depleted at about 1.5 minutes to 2 minutes of exercise.

Side note: it is a common belief that lactic acid causes fatigue, but this appears to be a myth. Lactate might actual be the preferred fuel source of the muscles and aid in hydration and acidity reduction in active muscles. See the Barbell Shrugged post with Dr. Andy Galpin here for more info on this subject.

Sports such as MMA, hockey, biathlon or long distance (i.e. 400-800m) sprinting rely heavily on the Anaerobic-Glycolytic system.



This is my favorite system to train, because the exercises are the funnest and you can really go all out. In fact, you will be required to go all out.

Training intensity should be at 85% of your heart rate max or above. You can use exercises like sprints, battle ropes, plyometric or any other high-intensity exercise. You will feel the burn. I discussed in a post from earlier this month about HIIT and how effective it is in developing your conditioning.

Focus on high intensity intervals, Tabata, or circuit training.

If your legs aren't burning and you're not out of breath, you need to go harder.

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Anaerobic-Glycolytic System Summary:

  • Used during high Intensity prolonged efforts such as long distance sprints, or repeated efforst of high intensity such as a hockey shift.
  • Efficiency peaks at about 5s of max intensity exercise and steadily declines
  • Training Intensity: 80-95% max exertion
  • Partial Recovery after significant exertion: 2-3 minutes
  • Full Recovery: 30+ minutes
  • Fatigue: decrease in performance, burning sensation in muscles, heavy breathing, nausea, 


Author: Mark Murdoch, Kinesiologist, Chiropractic Student. Have questions? Email me. I want to help! mark@leofitness.ca