Before reading if you have yet to read Part 1 do that now.
We need to answer the question, how is it possible to burn 9x the amount of fat doing interval training opposed to steady state or long distance cardio?
The answer comes down to pure science.
Think of your energy output as a box. The box represents the amount of time your system is elevated for burning calories. The more time you workout the bigger your box is and the more calories you burn. Makes sense right? Well, the question then becomes if I don’t have 20 hours a week to exercise or even 10 or 5 hours, how do I get the benefit of the full 20? Which by the way is a insane amount of exercise time!
Interval training allows you to get the benefit of exercise beyond the time you are actually working. If your heart rate when you do long distance training is 140-150 and you sustain that for 3-5 miles, and I have you do a 30 second interval that takes your heart rate to 170-180, there is a scientific shift in your body. You start to tap into different energy systems, challenge your body in new ways and transform your metabolism or the rate in which you process energy in (food and drink). After the 30 seconds of work you may have up to 90-120 seconds of rest depending on the exercise. During the rest is when the magic happens. As you are recovering from the sprint you are still burning more calories then when you were doing steady state cardio because your heart rate is still trying to recover from the peak levels.
I have over simplified this example for the sake of time but at the end of the training day I can elevate my metabolism by 24-48 hours just from interval work as apposed to minutes with steady state work.
So why aren’t more people doing intervals?
Because they are not easy. They are demanding and most people do not want to step outside their comfort zones. If you want to change your fitness, do something different. The definition of insanity is doing the same thing over and over and expecting a different outcome.