What are the "Energy Systems" and how to train them - Part 1: Background and ATP-PCr

Most individuals you see in the gym are there because they have been told it is good for them. They're told they need to get 150 minutes moderate intensity physical activity per week, which they usually do by slogging away on the treadmill, elliptical or stationary bike. But are they really better off? Are they actually getting fitter?

Our bodies, in their infinite sophistication, employ 3 primary energy systems which are the ATP-PCr, Anaerobic-Glycolytic and the Aerobic/Oxidative system

We will start by discussing how energy in the muscle is used. The muscles store a molecule called ATP (adenosine triphosphate), which releases energy when it is broken down. By storing ATP in the muscle, the body ensures that it always has energy on hand for a quick burst of effort. However, the muscles don't store enough energy for prolonged output. This is, in part, because ATP is a heavy molecule (it takes up to 80 kg of ATP to run a marathon while a single kg of Fat can provide up to 9,000 kcal of energy). Muscle contractions are constantly breaking down and using up ATP and the amount stored in the muscles is used up every few seconds. Obviously, if wouldn't be very efficient to hold 100 plus pounds of ATP just in case we needed to run for a few hours. Instead, we store fats and carbohydrates, which are more stable than an ATP molecule. The energy systems re-store the ATP and make new ATP to keep the muscles functioning. In a simple sense, the energy systems are recycling/processing plant, putting the ATP back together for the muscle to use again.


Which energy system is at play depends on the intensity and duration of exercise. The primary system providing energy during a 1RM back squat is different than the primary system during a half-marathon.


The ATP-PCr System

Without phosphocreatine, we would use up our energy stores in a matter of seconds. Instead, the phosphocreatine allows us to recycle the ATP we just used, extending the amount of every we can produce. This is the same creatine that you hear about bodybuilders supplementing with. While this more than doubles the amount of available energy "stored" in the muscle, the ATP-PCr system is still a short-acting system. At full capacity, the ATP-PCr system will only last up to 12 seconds. 

The upside of this system? It delivers a lot of energy. Fast.

Exercises such as a snatch, back squat or vertical jump are fueled, almost entirely, by the ATP-PCr system. Sports like sprinting and Olympic weight lifting rely heavily on this system.

It is important to train this system if you want to develop explosive strength and is essential in sports of high intensity. If you want to get faster, you need to train this system.


How to train the ATP-PCr system:

Training this system is simple, but not easy. It requires performing high at high intensity or effort. Using heavy lifts (such as a 3RM lift), plyometrics and sprinting type exercises will enhance be your best bet for training the ATP-PCr system. Take long breaks between repetitions of max effort.

Remember: if you're getting tired, you aren't training for speed. When the quality of your reps starts to go down, or you are feeling the burn of fatigue, you are transitioning into a different energy system.


ATP-PCr Summary:

  • Used during high Intensity, explosive movements (e.g. weight lifting, sprinting, punching)
  • Efficiency peaks between 0-2s of max intensity exercise
  • Training Intensity: 90-98% max exertion
  • Partial Recovery: 20-25 seconds
  • Full Recovery: 3-5 mins
  • Fatigue: start to slow (e.g. last half of a sprint), not out of breath, no 'burning' sensation in muscles
  • Training Frequency: 1-3 times per week. While the ATP-PCr system will recover quickly, there tends to be a need for additional recovery for the neruomuscular system and structural systems to adapt and recover.


Tomorrow: the Anaerobic System


B.Kin, Canadian Society of Exercise Physiology CPT

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