Let’s go ahead and jump into why it works so well. So the first reason is because during the exercise you burn stored sugar. So you burn through your glycogen stores. So with steady-state long-term cardio what that means is a 40-minute run instead of burning sugar for energy you’ll burn fat for energy during that workout. But when you’re doing high-intensity interval training you’re going to burn through your glycogen storage you’re going to burn through your stored sugar. And what this means for you is that because you burn your stored sugar during the exercise you’re actually going to burn fat for 24 to 48 hours post exercise.
Now the reason that you burn sugar during the exercise, you burn the stored glycogen is simply because it’s like a survival mechanism of the body. So, when you’re in this fight-or-flight survival mechanism the body needs quick energy. Because you’re doing this exercise at an intense level, the body says I need energy and I need it now. So what does the body do the body goes to sugar it goes to glycogen stores and it burns that for energy during the workout. And as I said, the great thing is, is that you burn through those glycogen stores, those sugar stores, then from there you’re going to burn fat for the next 24 to 48 hours. And now that is a solution for fat loss.
The next big reason it works so effectively for just preserving good health preserving good muscle mass but also burning fat is because it increases your growth hormone levels. The reason it works so well is because you’re burning sugar and because the workout is very intense the body’s going to raise growth hormone levels. And the reason it does this is not only for repair purposes of the body but also in order to help replenish those energy this oxygen debt which is owed. During this time essentially what’s going to happen is you are going to turn your body into a fat-burning machine as this debt is being repaid.
Now the next thing that happens and it works very effectively is doing high-intensity interval training will help keep your cortisol levels low compared to doing long term steady-state cardiovascular exercise. So what this essentially means is people who are marathon runners, people who are training for races that require them to run long distances, you know athletes. Essentially what happens is because of this intense training in its long duration essentially the cortisol levels get boosted and boosted consistently so any athlete who’s truly trying to take care of themselves and who is running a lot of distance is going to always be concerned with trying to keep their cortisol levels lower.
Now when you have high cortisol levels in the body, you’re going to have more inflammation in the body, you’re also going to not be able to burn fat as well. Cortisol will have a catabolic breaking down effect on the body. It’s okay in short duration in short-term but when it becomes chronic it becomes an issue. So long-term steady-state cardio doing it on a regular basis is going to boost those cortisol levels. However, doing high-intensity interval training is going to just boost them gently but not do it in a chronic way. So that’s why high-intensity interval training is better off than a lot of long-term steady-state cardiovascular exercise because it’s going to keep that cortisol low.