HIIT Energy Systems
The three energy systems are:
The ATP-CP System: This stands for ‘Adenosine Triphosphate Creatine Phosphate’ system. This is the quickest energy system that the body has access to and it uses up energy stored inside the muscles in its most basic form. It can only last a few seconds, although creatine can enhance this slightly.
The Glycogen Lactic Acid System: This is the second energy system. Once ATP-CP stores have been depleted in the muscle, the body will switch to the glycogen lactic acid system and this will use glycogen in the muscles. This can last for a couple of minutes but causes the build-up of metabolites in the muscle that cause the ‘burn’ sensation we associate with the gym. It also causes the build up of lactic acid in the blood, which makes us feel nauseous and eventually forces us to reduce our activity.
The Aerobic System: The last system that the body switches to is the aerobic system. Here, the heart rate works harder to pump oxygen to the fat stores. These get broken down and useable energy is then carried to the muscles to fuel movement. This can last indefinitely but puts the body in a highly catabolic state that breaks down muscle.