Burn calories while you sleep with the "after-burn" effect
The "after-burn" is something that the scientific community discovered around 1992 and they called it EPOC or Excess post-exercise oxygen consumption. Since its discovery there has been many different studies done to establish exactly how long this after-burn effect will be.
However they soon discovered that there is a certain minimum requirement necessary in order to activate this after-burn or EPOC effect and that is where HIIT came into the discussion. It seems that doing compound movements with a light or a heavy weight will activate this after-burn.
But the idea of this after-burn is certainly not a new one and as far back as 1918 when Harris and Benedict first discovered that when doing cardio it could burn more calories than where originally measured by the normal energy expenditure charts used.
This was truly the beginning of EPOC and how it is able to speed up the metabolism for up to 72 hours after a hard and intense workout is completed. When the objective is fat loss trainers quickly discovered that working out when on a calorie deficit is tough and leads to strength loss as there is simply not enough energy to give it all you got.
The idea that you can still remain in a calorie surplus and continue to lose fat long after the workout has been completed is something that got many fitness enthusiast's excited. The idea that we can now make a major difference to the speed of our metabolism just from one hard workout was inspiring to many bodybuilders.
It all has to do with training with less rest between sets and making sure that the heart rate does not diminish down to a resting heart rate while you are exercising with weights. It was the primary motivation for a high intensity interval (HIIT) studies that were done.
For the average bodybuilder at the time it would mean the lightening of the weights used as the rest between sets decreased. But the results were well-proven and the increased muscle gain achieved while not gaining any fat became an accepted fact in the health industry.
When compared to jogging on the road or jogging on a treadmill where one could lose up to 400 calories an hour it was shown that as soon as the jogging stopped so did the fat-loss and calorie loss. When these results where plotted against the calories used when doing HIIT the amount of calories burnt was less than when jogging was done.
But they quickly discovered that the EPOC or after-burn effect lasted on average about 36 hours after the workout. Bodybuilders got all excited about the fact that increased muscle growth was also recorded even if the weights used were less than the weights used in conventional training.
The point is that an increase in the metabolism is also an increase in the speed of protein synthesis which is the rate at which your muscles can repair. There have also been a few studies that show that the increased rate at which your metabolism can speed up is able to last up to 72 hours after the workout.
All this means that if your objective is to gain muscle and lose fat at the same time you do not have to go through the normal bulking up phase so that you can get strong and increase muscle. Using HIIT you can gain muscle while losing fat at the same time, so you can burn fat while you are sleeping.