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The big question.... is HIIT effective?

You may have heard of exercise programs such as Tabata, Meta Fit, or more recently seen the article on TV where Prof Jamie Timmons put Michael Mosley to the test on a 4 minute high intensity bike riding experiment. All of these regimes are based on HIIT.

High-intensity interval training (HIIT), also called high-intensity intermittent exercise (HIIE) or sprint interval training (SIT), is an enhanced form of interval training, an exercise strategy alternating periods of short intense anaerobic exercise with less-intense recovery periods. HIIT is a form of cardiovascular exercise. HIIT sessions may vary from 4–30 minutes. These short, intense workouts provide improved athletic capacity and condition, improved glucose metabolism and improved fat burning.

Short HIIT triggers anaerobic metabolism, which sky rockets your heart rate and melts away fat, without eating away muscle tone. So effective, that it keeps burning calories around the clock, up to 48 hours AFTER your workout is over.

How does it achieve this after burn? Because it elicits a powerful physiological effect known as EPOC (Excess Post-exercise Oxygen Consumption - informally called "The After Burn"). EPOC is a measurably increased rate of oxygen intake following strenuous activity intended to erase the body's "oxygen deficit".

The higher the intensity of the activity, the more oxygen and energy are needed to restore your body. As a result, the body continues to burn calories well after exercise is finished. And the good news, those calories come from stubborn fat! You can not workout long enough to equal the amount of calories you burn with the "After Burn" effect. So take into account the calories you burn after a workout, and more importantly, think about what you consume. There's no point working hard in the gym, only to undo all the hard work at the dinner table.

~ The EPOC effect is greatest soon after the exercise is completed and decays to a lower level over time (24-48 hours).

~ EPOC is accompanied by an elevated consumption of fuel. In response to exercise, fat stores are broken down and free fatty acids (FFA) are released into the blood stream. In recovery, the direct oxidation of free fatty acids as fuel and the energy consuming re-conversion of FFAs back into fat stores both take place.

~ Studies comparing intermittent and continuous exercise consistently show a greater EPOC response for higher intensity, intermittent exercise.