In earlier articles, we described that the body needs a constant supply of energy to function properly. If you are physically active, this energy demand of the body is higher. The energy you can intake comes from your diet in the form of macronutrients: proteins, carbohydrates, and fats. The body has 3 different energy systems. In this article, we will delve deeper into these energy systems and explain the difference between aerobic and anaerobic training.
The energy systems
The body mainly derives its energy from carbohydrates and fats. The energy compound stored in the muscles is called adenosine triphosphate, abbreviated as ATP. There are different ways in which your body can obtain ATP, namely through:
1. The phosphate system or ATP-CP system
2. The anaerobic system or lactic acid system
3. The aerobic oxygen system
Anaerobic training
Unlike aerobic training where oxygen is involved and there is a continuous elevated heart rate, anaerobic training is of short duration, hence there is no constant increase in heart rate. Strength training with weights is a good example of anaerobic training. This form of training is not suitable for developing the cardiovascular system but does help in muscle development.
There are a few anaerobic exercises to distinguish:
Isotonic exercises: these exercises cause your muscles to contract as they have to lift a certain weight. Weight can also be replaced by a certain resistance. Strength training with weights is a form of isotonic exercise.
Gymnastic exercises: these exercises are often aimed at improving flexibility and agility.
Isometric exercises: these latter group of aerobic exercises are exercises where your muscles have to work without your joints moving. An example of this is pushing a stationary car.
Aerobic training
When referring to aerobic training and anaerobic training, one refers to the energy systems that muscles use for their energy needs. As mentioned, your body derives energy from food, and whether oxygen is involved in generating this energy determines the difference between aerobic and anaerobic training.
Aerobic training is often a prolonged activity, with increased breathing and heart rate. Aerobic training basically means that more oxygen is consumed in the body. This form of training often strengthens overall fitness and the cardiovascular system. The cardiovascular system refers to the heart and lungs. When performing aerobic training, your heart rate should remain at a constant elevated pace for about 20 minutes. Some examples include running, rowing, cycling, and cross-training.
Difference between Aerobic training and Anaerobic training
The first way (ATP-CP system, or phosphate system) is the easiest and fastest way to generate ATP and this happens without the presence of oxygen (“anaerobic”). The name Adenosine triphosphate means that it involves adenosine linked to three phosphates. The splitting off of one of these phosphates releases energy. When ATP is used to provide energy (about 7.3 kcal per ATP), what remains is ADP (Adenosine diphosphate, adenosine with two phosphates) and a free phosphate molecule. CP stands for creatine phosphate stored in the skeletal muscles. Before ADP can release energy again, this phosphate group must be replenished, which is supplied by the stored creatine phosphate in the body. In this process, carbohydrates, fats, or proteins are not used. This way of generating ATP mainly occurs during very intense, short-term forms of exercise. Think of short sprint activities (100m), powerlifting, but also in high and long jump. Through this method, only 10 to 15 seconds of energy can be supplied to all muscles, after which exhaustion occurs. It is also not possible to store large amounts of ATP in the muscles, only a small amount for a few seconds of intensive activity. This system is immediately ready to provide energy and is therefore always active first. This is also the case, for example, when you get up from your chair, although this (for healthy people) is naturally not an intensive action. Nevertheless, the energy supply mainly comes from the ATP-CP system.
In the Anaerobic energy system, glucose and glycogen are broken down in the absence of oxygen, and the end product of that reaction is lactic acid. In the aerobic energy system, the process is the same, except that there is oxygen present, leading to a different end product called pyruvic acid. This end product is important for the second process of the aerobic system called the Krebs cycle. Pyruvic acid is converted into the molecule acetyl coenzyme A. The complete oxidation (burning with oxygen) of this molecule produces two units of ATP with byproducts carbon dioxide and hydrogen. These hydrogen ions then combine with other enzymes and ultimately provide energy for the electron transport chain. The complete metabolism of 1 glucose molecule can generate about between 35 and 40 ATP in this way. In other words, 18 times more than through the Anaerobic system.
Fat can also be burned in the presence of oxygen. Triglycerides must first be converted into free fatty acids. These are then converted into acyl-CoA molecules, which in turn enter the Krebs cycle. Fat can produce 129 ATP molecules in this way, which is more than with carbohydrates. On the other hand, burning fat requires more oxygen to generate ATP. This makes the energy supply from fats less efficient, so carbohydrates remain the preferred and designated fuel for ATP production.
The Aerobic system is not quick in producing ATP but has the capacity to produce energy for a much longer period. A larger fat store can be built up than glycogen from carbohydrates, which can only provide energy for 30 to 40 minutes of maximum effort. An “excess” of carbohydrates is then converted into body fat as reserve fuel with the help of insulin.
Conclusion
The body has 3 energy systems to supply its continuous energy needs. The difference between anaerobic and aerobic training lies mainly in how the body and muscles obtain their energy. If the body generates it with the help of oxygen, we speak of the aerobic system. If oxygen is not involved, we speak of the anaerobic system.
To conclude with an example:
If you start running, your body initially starts with an anaerobic training form to obtain its energy. After the first 3 minutes, oxygen comes into play, and your body switches from an anaerobic phase to an aerobic phase.
