You might think that knowing about the body’s different energy systems is only useful if you’re goal is to increase fitness, but if you’re looking to build muscle and get a six pack then minimising your body fat percentage is vital. The basic rule of achieving this is to use more calories that you take in, but this can sometimes be difficult to do without dropping below your basal metabolic rate (BMR). Aerobic exercise only burns calories while you’re actually doing it, but anaerobic exercise such as lifting weights or interval training burns calories for many hours afterwards by boosting your metabolism.
Energy used by muscles is known as adenosine triphosphate or ATP, which is stored in the body, but as there isn’t much of it available it has to be made on demand. This is dependent on the availability of oxygen, which is why there are 3 energy systems that can be utilised.
The Phosphocreatine Energy System
Phosphocreatine is stored within the muscles themselves and is immediately available for use. It doesn’t require oxygen and it doesn’t produce any lactic acid, but it only lasts for about 10 seconds after which it takes a while to recover. Explosive exercise such as lifting weights, high intensity interval training, or running a 100m sprint, make use of this energy system.
Lactic Acid Energy System
If the absence of exercise without oxygen continues, lactic acid levels will begin to grow. A by-product of intense exercise, lactic acid can be converted back into energy with increasing efficiency as your fitness level improves. Lasting no more than 3 minutes however, even this system will fail, so you will either have to rest or lower the intensity of the exercise.
Aerobic Energy System
If you lower the intensity but continue to exercise for more than 3 minutes you will be doing so aerobically, which means with sufficient oxygen available from your cardiovascular system (your heart and lungs). This is limited only by your fitness level. The by-products here are water and carbon dioxide, which the body gets rid of when you breathe. Although you can exercise for much longer with this system, as I said earlier it only burns calories while you are actually doing it.
Make the most of the anaerobic energy systems either lift weights for short, intense sets, or do high intensity interval training with equally short work / recovery phases.
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