What is HIIT?
High Intensity interval training (HIIT) is the alternating of short intense periods of exercise followed by less intense periods for active recovery.
HIIT training is commonly referred to as being a superior form of improving cardiovascular fitness and burning calories, mainly because it offers greater efficiency in a short amount of time. Considering people have busy lives, efficiency is a good selling point. Typically, HIIT session may last 12-20 minutes.
Logically it make sense, but at the end of the day, HIIT is not any better when it comes to total calories burned in a 24 hour period. The difference is not significant enough to warrant choosing one over the other, unless time constraints are an issue.
The mechanism behind HIIT is EPOC. EPOC is the body’s use of oxygen to recover and return the to normal function. The use of oxygen burn calories. Consequently, the greater the EPOC, the more calories your body will burn after exercise. The higher the intensity, the greater the EPOC.
There is an inverse relationship between duration and intensity. The greater the intensity, the shorter the time required to produce significant EPOC. For example, if you ran 2 miles in 12 minutes, you will have a much greater EPOC than if you took 20 minutes. This make sense in theory, but in the real world, things are different. With HIIT, there are diminishing returns and limitations. Typically it is not safe to participate in HIIT for more than 20-25 minutes per sessions. Also, to prevent burning out, limit HIIT to a maximum 3 times per week. Also Studies have shown that when energy expenditure is measured after intervals and continuous bouts of exercise after 24 hours, they are about equal. You can have a greater EPOC if HIIT lasts for 45 minutes to an hour, but there are diminishing returns. Ultimately, if you want to burn a significant amount of calories safely, spend more time exercising during steady state cardio and weight training. HIIT has it place if efficiency is more important to you.