The five energy systems

This article explores the different energy systems behind the training zones. The different systems will be described from small to large. All systems are trainable, which means that they can all improve when training is done in the different training zones.

ATP
ATP stands for Adenosine TriPhosphate. A mouthful for the non-chemists among us, but ATP is the energy supply for our body. In other words, all energy-consuming processes in our body, such as movement, cardiac activity, transport and tissue building, are triggered via ATP. ATP consists of 3 molecules of phosphate (hence "tri"). ATP is the smallest usable form of energy and actually causes the muscles to contract. In the muscle cell, it ensures that certain muscle parts (actin and myosin) slide into each other, causing the muscle to contract and thus shorten. ATP is therefore necessary for simple movements, such as blinking an eye and holding a cup of coffee, but it is also very important for sports performance. The ATP is only in limited supply in muscles and is used up within seconds. It must therefore be constantly created and supplemented. ATP replenishment occurs through the breakdown of other energy-producing products described below. When ATP is consumed, one phosphate molecule is consumed, leaving "low-energy" ADP (Adenosine DiPhosphate), a molecule with two phosphate molecules.

Creatine Phosphate 
In addition to ATP, there is a constant supply of creatine phosphate in the muscle cells. Creatine phosphate consists of creatine and one phosphate molecule. The role of creatine phosphate is to turn ADP back into ATP. It does this by replenishing the removed phosphate molecule. The creatine then remains alone. The supply of creatine phosphate in the muscle cells is sufficient for about five to ten seconds of muscle work. 

Lactic acid 
A well-known term that athletes often say is "my legs are completely full" or "I was completely sour". This all has to do with the production of lactic acid and lactate (anaerobic combustion or combustion without oxygen). Lactate is continuously produced and broken down in the body, including at rest. The more the exercise intensity increases, the more lactate is produced. The resulting lactate is reused as fuel by the muscles. However, some of it enters the bloodstream and is used as fuel in other organs (heart muscle, brain) or converted into sugar in the liver. The amount of lactate in the blood provides an indication of how acidic an athlete is. For this reason, lactate is often pricked during exercise tests and training. 

Carbohydrates 
An important energy source for athletes are carbohydrates. The term carbohydrates is a collective name for sugars and starch. Carbohydrates are for example in the "fast" sugars such as table sugar and sports gels, but also in meat, potatoes, rice and pasta (the "slow" sugars). The breakdown of carbohydrates is relatively fast, causing ATP to form quickly (of course not as fast as with creatine phosphate). That is why carbohydrates are very important in sports performance. Carbohydrates are stored in the body to a limited extent (muscles and liver), which indicates the importance of sufficient food during (long-term) sports practice. After about two hours of intensive exercise, the carbohydrate supply in the muscles can be almost empty.

Fats 
Fats are also an important source of energy during long-term exercise. Fat is burned especially during low intensity. Fat burning is slower than carbohydrate burning, so energy (ATP) is slowly released. Research shows that most fat is burned at an intensity of approximately 60% of the maximum heart rate. If you want to get rid of fat tissue, it is best to exercise at a low intensity. The secret of predisposition to endurance sports often lies in how long a person continues to use his fat burning process. Differences can therefore be made with this. The more you can save carbohydrates, the more "fast" energy has left for the final sprint. Protein Although proteins are not the primary energy source, proteins are sometimes used as fuel. Particularly when the stock of carbohydrates in the muscles is used up, the body's own proteins (eg muscle tissue) are burned. It should be clear that this is not a desirable situation, because then there is muscle breakdown. A good nutritional status before, during and after exercise is therefore essential.