Using HIIT to help you workout during a busy week
The human body expends about 5 calories of energy to consume 1 liter of oxygen. When an activity uses multiple muscle groups at a high level of intensity, more oxygen is needed, and more calories are burned. HIIT workouts that involve both the upper and lower body can be particularly effective for those who want to lose or maintain weight.
HIIT primarily uses the anaerobic energy pathways, which run out of adenosine triphosphate (ATP), the chemical muscle cells use for energy, rather quickly. So, not only do you use energy during the work interval, but during the recovery interval, muscle cells continue to produce and replace ATP for the next high intensity bout. Whether you are exercising your hardest or taking a few moments to catch your breath during an active recovery interval, your muscles are always working during a HIIT workout.
With HIIT, you will not only burn calories during the workout, but will continue to burn calories after the workout is over, making it an extremely effective use of your time. Excess post-exercise oxygen consumption (EPOC) is the term that describes how your metabolism continues to consume oxygen (and burn calories) for hours after a HIIT workout. Once you are finished with your workout, your muscles will continue to use oxygen, along with fat, to replace the ATP and repair the tissues damaged during the exercise.