With the launch of our newly implemented WODify Pulse Heart Rate System at our facilities, we are keen on members gaining further knowledge of how and why we structure our classes and workouts the way we do. This will hopefully enable a better understanding of the physiological responses and benefits of our training methods.

Energy Systems is the first topic on our hit list, so here we go, lets dive in……

Energy is needed by every cell in the body to function, whether that be muscle contractions for movement and exercise, regulation of body temperature, sleep, breath or any other bodily function.

All energy is produced from the breakdown of the molecule ATP, adenosine triphosphate. ATP is found in all cells of the body – but due to it being a large molecule there is a limited number of ATP in cells.

So when it comes to physical movement and exercise the ATP gets used up very quickly and needs to be replenished to continue with the exercise.

We have 3 Main Energy Systems that can replenish ATP

1. ATP-PC System (aka Alatic System)
2. Glycolytic System (aka Lactate System)
3. Oxidative System (aka Aerobic System)

The ATP-PC and the Glycolytic System are anaerobic (oxygen is not required to produce ATP) and the Oxidative is aerobic (oxygen is required to produce ATP).

The ATP-PC System is used for maximal power output exercises such as all out effort sprints, jumps, 1RMs etc and works for 6-10 seconds.

The Glycolytic System relies massively on the rapid breakdown of Carbs in the form of glucose that is constantly circulating in the blood stream, and as well as this, glucose is stored in the muscles and liver in the form of glycogen. When exercising at maximal effort for periods of 10-90 seconds – the glucose and glycogen rapidly go through a process known as ‘glycolysis’ to produce ATP, this is why its important to have carbs pre and post training. During this process lactate and hydrogen ions are produced and it is in fact the presence of the hydrogen ions in the blood and muscles that make it more acidic and leads to fatigue and the buuuuuurning sensation. Poor old lactate gets a bad rep unnecessarily for being the cause! For those that enjoy knowing more about this area of fitness and fatigue, Dr.Andy Gaplin does a great podcast interview on ‘Muscle Expert Podcast’ that talks about this indepth.

The 3rd Energy System, the Oxidative System involves the use of oxygen to produce ATP – during this system 2 processes are used. The Krebs Cycle (those that studied Biology at A Level I’m sure will have flash backs of this) and the Electron Transport Chain. So these two processes can’t produce ATP as quickly as the first 2 energy systems but it can produce ATP continually for a far longer period of time! This system can use Carbs, Fats and Protein to fuel the energy system. Fats and Proteins however take far longer to break down in order to produce ATP.

So from a nutrition perspective you can see why its important to include the 3 main macronutrients in your diet to fuel performance and exercise. If you are on a low carb diet you are restricting you bodies ability to fully utilise certainly the Glycolytic and Oxidative systems. Its also important to understand that your body also utilises all 3 energy systems simultaneously at times – but more often then not there will be a predominant energy system working.

This is why it’s important that we train all 3 energy systems to become more productive and improve the efficiency of producing ATP. When we programme at ION that’s why there is always a lifting element – whether it is an explosive Olympic lift, a Heavy Squat or all-out effort on the Echo Bike for a very short space of time, this puts a huge tax on the ATP-PC system. If we do an all out 500m Row or 400m Run that will massively tax the Glycolytic system. With a lot of the CrossFit style workouts that are over 10 mins – this becomes predominately oxidative.

With Triangle Conditioning, Assault Concept or CrossFit workouts where we have intervals and working up to 90 seconds at a time followed by prolonged rest periods we are putting big demands on both the glycolytic and oxidative systems.

This method of training, known as (High Intensity Interval Training) will help you to improve your recovery and regeneration of energy in-between intervals to allow you to work harder during and why a lot of endurance athletes use H.I.I.T style training to improve rather than just continual long duration efforts.

So believe it or not there is certainly method behind the madness within our daily classes that are working towards assisting you improve your all round fitness and improve all 3 energy systems.

Energy Specific System training is certainly a buzz word at the moment and so you understand when people do talk about it – all they are talking about is the work : rest ratio they are using.

If you are looking to train specifically one energy system – then this where work and rest periods are manipulated. As you can see from the work : rest ratio chart (left) the higher power output efforts are the ones that require longer rest periods (from a ratio perspective) in order to fully replenish ATP stores and clear the muscles of any unwanted by products.

To simplify the energy systems further I have to use an analogy that I heard on another podcast that I thought was excellent.

‘Gambling and Energy Systems’.

Hopefully then this makes it an easier way to remember!

ATP is your currency and think of it like this….first up at the poker table you are going to gamble with cash. Cash is your ATP-PC system. As the house always wins, you will  run out of cash pretty quickly. You will reach for the wallet and there will be none left…….

When your wallet is empty, you will make a quick visit to the ATM machine. Your bank account is your Glycolytic system. As you are forced from the table you will slow down gambling, however, you have more money in your account than you initially have in your wallet so you will be able to gamble longer. The glycolytic system lets you train at a moderate pace for a moderate duration, for a couple of minutes of 100% effort at roughly 80% of your top speed.

You have spent all your cash and now your bank balance is on empty. It’s time now to go back to work to build up the bank account again so you will be able to once again return to the tables. Work is our Oxidative system. You can make more money to keep gambling, but you have to leave the casino, go to work and get paid before you can come back. You can repeat this cycle for a long time, but it is a slower process and the pace at which you can gamble will be greatly reduced. The oxidative system is low power but long duration, and will include aerobic activities that last longer than a few minutes.


Hopefully this makes Energy Systems and training methods a little bit clearer – we’ll be testing you in class on what energy systems are being predominantly used 🙂


Robin Sowden-Taylor









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