Exercising with limited oxygen to the working muscles makes the exercise harder than usual. This increased intensity signals the brain that "damage" is occurring to the muscle (although no muscle damage is occurring). This signal releases hormones to aid in tissue recovery and repair. These hormones include growth hormones, insulin growth factor 1, and testosterone.

Depriving oxygen to a working muscle will make the muscle work harder and use a different energy system (Cori Cycle). During this process, the body has to generate energy differently, creating a burning sensation in the muscle. This feeling is similar if you switch from a light jog to an all-out sprint. This switch signals to the brain you are working harder than usual and creates a cascade of physiological adaptations to help build strength and grow muscle. You will also experience muscle swelling as fluid is pushed into the muscle cells. This swelling is similar to the feel you get if you perform a lot of bicep curls and have the temporary ‘swollen’ effect.

While reducing the amount of blood flow to the heart, the heart has to beat faster to push more blood to the entire body. Therefore, you will feel your heart rate increase. This increase in heart rate will create a training effect at much lower intensities and time than usually required with regular aerobic training.