EPOC or the “Afterburn Effect”
I’m going to share this recent article on breaking muscle and clear up some of the understand around HIIT, EPOC and or the Afterburn Effect.
First EPOC stands for Excess Post-exercise Oxygen Consumption. It’s an increase in oxygen uptake above resting levels that occurs after exercise. Increased oxygen consumption requires energy, so EPOC means that you burn calories even after an exercise bout.
The article goes on in terms of its practical implications.
They used the data from the Skelly Study as an example.
In that study, participants breathed through a mouthpiece, and their exhaled air was analyzed to measure oxygen consumption and calculate their energy expenditure. Expired air was collected every few hours over a 24-hour period, including for one full hour during which participants rested or exercised. During that hour, they either;
- rested for the entire hour,
- rested for 10 minutes and then cycled for 50 minutes continuously at a moderate intensity,
- or rested for 40 minutes and then did 10 x 60-second high intensity cycling intervals with 60 seconds’ rest in between.
During those one-hour periods, here’s the average number of calories they burned:
Rest: 125 calories
50min cycling: 547 calories
20min intervals: 352 calories
Over the full 24 hours (including the exercise period), here’s approximately how many calories they burned:
Rest: 3005 calories
50min cycling: 3464 calories
20min intervals: 3368 calories
These participants burned more calories during 50 minutes of continuous cycling than they did during the 20-minute interval session, and they burned more total calories over 24 hours when they did continuous cycling. The difference between continuous cardio and interval training in this case is only about 100 calories over 24 hours. More importantly, as you would expect, both continuous cardio and interval training burned more calories than not exercising at all (about 350-450 extra calories over 24 hours).
So you’re probably going to burn a similar amount of calories if you do a short but very intense interval session, or a long, moderate intensity cardio session.
If you do a long interval session, you should get a bigger EPOC effect than if you did the same duration of moderate intensity cardio, but remember that intervals need to be performed at a very high intensity to get the benefits. They doesn’t or wouldn’t recommend stretching an interval session past about 20-25 minutes, because most people won’t be able to maintain the necessary intensity over that amount of time.
So they go on – trying not to discourage anyone from interval training. Intervals have been shown to be a very time-efficient way to increase fitness and promote weight and fat loss. The mechanism for that just doesn’t seem to be extra EPOC.
But here’s what you should understand - the mechanisms for the benefits of interval training are:
- Hormonal and/or Appetite changes that promote fat burning and therefore decrease caloric intake,
- they increase the body’s ability to preferentially use fat as a fuel.
Any both of those would result in weight loss over time.
So remember - the reality is that many people struggle to lose weight, and their will be misleading messages from the fitness community (even when they appear to be backed by research). Don’t get bogged down with calorie counting or performing only this “right” type of supposed exercise.
I’ll quote another spot in his article..
“THAT KIND OF TRANSACTION MINDSET, WHERE YOU EARN FOOD BASED ON CALORIES YOU’VE BURNED WITH EXERCISE, IS A RECIPE FOR FAILURE.”
So, it’s good to know the difference – don’t think one is better than the other. I use to claim things about the “afterburn effect” and I was exaggerating the claims probably.
I added that eating 2.5hrs before a workout was best and to limit your carb/prot/fat intake to somewhere around 25%C/30%P/45%F and under 400cals. I’m basing this on a 180lb male wanting to lose 20lbs.
This way your burning through your carb reserves and basically depleting them as much as your body allows during your workout. But you still need energy so your body is going to start shoveling unwanted fat into the fire to be used.
And then the theory - your going to burn even more calories at a faster pace over the next 14-16 hours after the gym most of which is actually going to be unwanted fat that you want to get rid of it as well. So that's where the massive former fat loss claims with high Intensity Training and all the studies being done on it to show better fat loss post workout. So remember less carbs as you lead up to your workout therefore you have less to burn through during. Then post workout you may replenish your glycogen stores with some fruit or your recovery drink/shake that contains simple digestible carb powder.
To finish - That’s why we provide the type of exercise we do, we provide variety, and exercise that you enjoy. We dose out intensity that’s appropriate for you all and a product you can maintain long term.
Interval training can be great for you. As can continuous cardio. Just takes longer. Any type of physical activity that you can perform safely is great for you. Just do something and don’t worry about what’s going to burn more calories, or if this exercise is better than that exercise. Come to the gym and get moving!