ATP – What is it, why is it important and how is it made?

ATP or Adenosine Triphosphate is the fuel our cells use for whatever they are doing, a brain cell uses it to think, muscle cell to contract and every other function in our body is fuelled by ATP.

For such an important resource for our bodies, we do not store a huge amount, approximately only 50g in our whole body. If our ATP levels drop below 50% our cells would start to shut down and die. So, we are only ever 25g of ATP away from the end!

When ATP is metabolised by our cells, we are left with Adenosine Diphosphate or ADP. Tri meaning 3 and Di meaning 2 means that to turn Diphosphate into Triphosphate we need to find that third phosphate from somewhere. Fortunately, our body being the clever machine that it is has 3 different systems in place for producing ATP.

The three systems are, the Phosphagen System, Aerobic system and the Anaerobic Glycogen Production or Lactic acid system. We will now look at each individually.

Firstly, the Phosphagen system. This is the way the body can quickly produce ATP for short, highly intensive burst of exercise. Activities like Sprinting, Olympic Lifting or throwing a Javelin. ATP is made by breaking down Creatine Phosphate to reform ADP into ATP. The remaining phosphate is then transported by our blood to our kidneys where it is reformed into Creatine Phosphate. This method of production requires no oxygen and the Creatine Phosphate used is predominantly found in the phosphocreatine in our muscles. Although this method can quickly produce ATP, we cannot use it for very long, this method of energy production is only really useful for burst of 5-10 seconds.

Next, we are going to look at the Aerobic system. The is the only method of the three which uses Oxygen in the production of ATP. This system is incredibly energy efficient but that also means it is a slightly slower process than the other two methods. It does mean it will provide far more ATP from the same amount of fuel than the other two. This is achieved by the oxidation od acetate derived from fats and broken down into carbon dioxide and chemical energy in the form of ATP. The process in which fat is turned into ATP is known as the Krebs cycle. This is the main resource for our ATP production for every activity lasting longer than a couple of minutes.

And then finally, the Anaerobic Glycogen Production or Lactic Acid system. In this process the fuel is coming from the breakdown of carbohydrates and again this process does not require the use of oxygen. However, there is a downside to this method of production, it is inefficient, there is an incomplete breakdown of glycogen as well as the production of lactic acid which inhibits the contraction of the muscle, causing fatigue. This is going to be the main system for any activity between 10 seconds and two minutes.

In reality we are never using any one of the systems at a time, our body is very good at adaption. So all three systems will be keeping our ATP topped up for us. But it is hugely important to understand how ATP is made when building a training plan or exercising in the gym as it will enable you to better understand where your energy is coming from and plan rest periods between sets or reps better.