Interval training provides many benefits to the aerobic system. Perhaps the most important benefit is the increase in its ability to produce energy. This is due to an increased ability to consume oxygen during exercise. Several experiments have produced results demonstrating that interval training increases both peak VO2 (Perry, 2008) and VO2 max (Sloth, 2013). Oxygen is necessary for the conversion of sugar, proteins and lipids into usable energy. The chemical processes involved in aerobic metabolism are not possible without oxygen, particularly the electron transport chain, the mechanism responsible for 95% of the ATP needed to keep cells alive. Oxygen is needed to capture the large amount of energy locked in the chemical bonds of pyruvic acid, the product of anaerobic glycolysis. Thus, the more oxygen the body is able to consume, the greater the production of ATP via the aerobic system. Not only does interval training increase the amount of oxygen the body can consume during exercise, but also its efficiency in delivering oxygen to key muscles. . Researchers attribute this to increased stroke volume. Stroke volume is the volume of blood pumped by a ventricle of the heart in a single beat. The body can only continue exercising when the performing muscles receive oxygenated blood. It is therefore crucial that the oxygenated blood supply remains open throughout exercise. Stroke volume may increase through higher left ventricular contractile force and/or increased cardiac filling pressure, which increases end-diastolic volume and resulting stroke volume (Laursen, 2002). In addition to increased stroke volume, researchers identified increased activity b...... middle of article ......l., 1987). In a study in which participants performed sprint interval training (Bayati, 2011), there was an increase in peak blood lactate between before and after training, indicating a greater capacity for anaerobic glycolysis. This increase coincides with an increase in maximum power, average power and total work. Sharp et al. (1986) reported increased blood lactate concentrations and total work performed during a 45-second maximal cycling sprint after eight weeks of intense sprint training in untrained subjects. These data were reported in conjunction with an increase in the glycolytic enzyme phosphofructokinase (PFK), suggesting that the increase in lactate and total work values ​​was due to an improvement in glycolytic efficiency. All these studies suggest that interval training improves the performance of the anaerobic system and activates the aerobic metabolism more easily...