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The Energy Systems for Endurance Athletes

Updated: Dec 11, 2019

The feeling of taking your body to its limits during endurance events is a love hate relationship for an athlete. Yes, it is very painful, yes you might feel a little bit sick and yes, your heart is pounding out of your chest but for some reason athletes love it and finding themselves craving more! But what defines these limits and why can’t we keep working harder for longer? .

Training at the right intensities is often where athletes don’t always get their training right and when the dreaded plateau can kick in. The body has the most amazing ability to adapt and improve, this also means that training intensities must also be adapted and increased. Training zones by heart rate can be massively useful to consistently improve and keep achieving PBs. In affect the body is always working in one of three zones, these three zones link to the energy systems within the body.

ATP-PCR System – Immediate zone (up to 10 seconds of high intense activity)

The Lactic Acid System – Short term Zone (1-3 minutes of intense activity)

The Aerobic System – Long term zone (continuous steady state exercise)

The ATP-PCR system provides immediate high intense energy; Adenosine Triphosphate (ATP) is stored within the muscles and is ready to provide energy at any given moment. Leaving the detailed science behind how this occurs behind (ask us about this during your next treatment as it is very interesting) all you need to know as endurance athletes is that this energy system exists and will rarely be used during training or competition. Try running up the stairs after being sat down for a while to utilise this system (your body won’t like it).

The Lactic Acid System (Glycolysis) now this is where things start to get a little scientific. The process of utilising ATP to create muscle contractions remains the same, it is the process of resynthesizing ATP that differs. This time Glucose is used to form ADP back into the useable ATP. Initially glycogen (stored in the muscles) is converted in glucose which can then be used for glycolysis. This is the process of taking ADP and Pi back into ATP molecules, anaerobic glycolysis requires 2 ATP, but it produces 4 ATP, a net gain of 2. As with all chemical reactions waste products are created, in this case Pyruvate and Hydrogen Ions. A build-up of Hydrogen is what increases acidity within the muscles and causes that burning pain we experience. With me so far? Next comes the really interesting and important part….

The excess pyruvate and hydrogen ions then bind together creating a substance called lactate (very different to lactic acid). To most endurance athletes this is a dreaded word however what is to follow will make you change your mind. As intense exercise begins, pyruvate and Hydrogen are rapidly produced through the lactic acid system, these then begin to bond together (1 pyruvate attaches to two hydrogen ions, and Lactate is quickly produced. When O2 is present lactate can be removed from the muscles and delivered to the kidneys where it can be synthesised back into pyruvate and then into glucose which can be used to start the process over again. If lactate did not form, we would not be able to get rid of Hydrogen and muscle acidity would rise rapidly bringing us to a shuddering holt very quickly. This therefore works on a sliding scale factoring in physical fitness, exercise intensity, exercise duration, O2 available. The harder we work the faster lactate is produced, there will become a point where the body cannot get rid of the lactate faster than it is being produced (lactate threshold) and eventually too much hydrogen is left within the muscles and exercise intensity must either decrease or stop.

The key to middle distance events (anything from 60 seconds to around 60 minutes) is making this system as efficient as possible so the body can work harder without increasing lactate le

vels. So how do we do that? What has been labelled as interval training is the best way to increase the bodies tolerance to lactate, and to improve the rate at which the body can remove lactate and can produce ATP through Glycolysis.

To improve the body’s ability at getting rid of lactate you want to completely fill the muscles by working near to max and then by completely resting at a ratio of 1:6, so 1 second work to 6 seconds rest. So for running this might be a 60m sprint followed by a minutes rest (presuming the sprint takes around 10 seconds).

To train the body to break down lactate back to glycogen and resynthesise ATP through glycolysis for you want to bring the ratio down to 1:3 however the intensity of work must also be reduced. So You want to be training at just above your lactate threshold so lactate is being rapidly removed and broken down but not faster than it is being produced, (400m for a run session) 1 minute on 3 minutes rest.

For more experienced athletes you can shorten this ratio even further to 1:2, this begins to increase the bodies tolerance to lactate within the muscles. When intensity is increased, and lactate is building within the muscles the body can continue through this for longer until the point of exhaustion is reach. Workout duration should be kept short but repeated 10 times, or until exhaustion. These sessions shouldn’t be used all year round, only in preparation for key or target events. After any interval session a long cool down should be done to put the balance back in oxygens favour and ensure lactate is completely flushed out of the muscles. Interval type sessions should be used sparingly, twice a week and on a fresh body, ideally after a rest day.

The Aerobic System produces ATP in the same way as the lactic acid system however the presents of sufficient O2 means hydrogen is not produce as a by-product, instead a substance called acetyl coenzyme A is. This then enters the Kreb cycle which takes place in the mitochondria. The kerb cycle only produces 2 ATP and Hydrogen is still a by-product, along with carbon dioxide which is removed from the body through respiration. The most complex part of the aerobic system is the Electron transport chain. This system can produce 34 ATP and hydrogen combines with oxygen to create water which is easily removed from the body. Although scientifically this is the most complex system all you need to know in terms of improving it is that long steady miles are key. Sometimes referred to as base miles, training at a constant pace for more than 15 minutes. Steady state exercise allows the body to develop more mitochondria in terms of how many you have and how efficient each one is. Fartlek training (varying speed and intensity) as long as exercise is at a level where no rest is needed throughout the session.

Now that is the theory of how the amazing human body produces energy for exercises, now its time to put the theory into practice and hopefully armed with this knowledge you will see big improvements in the way you train and ultimately in your performances.

If you want to know more a The Energy Systems

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