Energy systems are the chemical pathways that provide the energy we need to carry out physical activity. All energy systems for exercise produce ATP (adenosine triphosphate) as an end-product. ATP is simply energy, just like petrol is required in a car for movement, our body needs ATP for movement. The body relies on three energy systems for exercise: ATP-PCr (adenosine triphosphate-phosphocreatine), anaerobic and aerobic. The energy system we use depends on the intensity and duration of exercise we do.

ATP-PCr energy system

This is known as the immediate energy system. ATP and PCr are stored in the muscles. This means they can provide an instant source of energy when we start exercising. This system is active during all out exercise such as a 100-meter sprint, lifting weights or other high intensity exercises. But it doesn’t last long, after about ten seconds of maximal intensity exercise we will need assistance from other energy systems.

Anaerobic energy system

Anaerobic means without oxygen. The anaerobic system is the next fastest system after ATP-PCr. This system uses glucose which we get from carbohydrates in the diet. Glucose undergoes a process called glycolysis which doesn’t require the presence of oxygen to produce ATP. The energy from this system is a key contributor for moderate to high intensity exercise lasting one to two minutes. An interesting fact about the anaerobic system is that lactic-acid is produced as an end product. Lactic acid is what sometimes causes us to have sore muscles after exercise and contributes to the ‘burn’ we feel when doing those squat jumps. Proper warming up and cooling down can help to prevent this – something which The Life Plan Physio’s cover in their workshops!

Aerobic energy system

Aerobic means with oxygen. This energy system is used when there is enough oxygen present to meet the oxygen demands of the activity. It is fuelled by carbohydrates, fats and to a lesser extent protein. Because this energy system requires oxygen to produce ATP it takes a little longer to kick in compared to the other systems. But it means we can exercise at a light to moderate intensity for much longer. For this reason, we are likely to use this system during endurance exercise.

These energy systems don’t work in isolation, we don’t just switch from one to the next. It can be thought of as more of a continuum or sliding scale with one system being more dominant than the others at a point in time.

All three energy systems have one thing in common, they need fuel. This is why it is essential to have both the right training and the right nutrition to achieve your fitness goals! Each of The Life Plan’s programmes have tailored fitness and nutrition advice to ensure you have the right fuel for your goals. Learn more about The Life Plan’s programmes here.