Is The “Afterburn Effect” A Real Thing?

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In the realm of fitness buzzwords and jargon, the term “afterburn effect” has been tossed around so much, it’s hard to know what it really means. Essentially, the premise of afterburn is that after specific workouts that push your body to the max your body responds by burning calories even after the workout is over. Some people say that your body can continue to burn calories up to 24 hours after an especially hard workout. Sounds like a pretty sweet deal, right? 

With more and more research coming out about the afterburn effect, we can really get a clear idea of how many calories we actually burn post-workout and what this means for our health. So is afterburn just a trendy myth hocked to get you to go to grueling workout classes? Or is it actually a useful and scientifically proven method to help you burn more calories outside the gym? Read more to find out the truth behind afterburn. 

What Is The Theory of The Afterburn Effect?  

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Just like creatin goes with bodybuilding and yoga comes with stretchy pants, the afterburn effect goes with HIIT style workouts (AKA high-intensity interval training). HIIT workouts are essentially small reps of exercises performed at your maximum capacity for short periods of time. So, for example, instead of going for a 40-minute jog a HIIT style workout would be a 15-minute sprint.

Because high-intensity training places greater demands on your body, it has to work harder to recover – to metabolize lactic acid, bring your core body temperature down, slow down your breathing, replenish muscle glycogen stores, etc. These all burn calories! Whereas when you exercise at a moderate intensity your body recovers relatively quickly.  So, what afterburn or it’s more scientific name Excess Post-Exercise Oxygen Consumption (EPOC) refers to is the fact that you continue to use oxygen and burn calories at a higher rate after you finish a high-intensity workout.

Essentially, afterburn is a state in which your body is trying to actively recover from very intense exercise such as HIIT workouts and through that recovery process, you burn extra calories. Ta-da! You basically have a degree in kinesiology now. 

Certain types of HIIT workouts, like Tabata, where 20 seconds of all-out effort is followed by 10 seconds of rest, are one way to trigger the afterburn. Other HIIT routines, such as density set training or the 5×5 workout can also set your body into EPOC. The key with any of these programs is that you need to be working hard. We’re talking exercise performed at 70 to 85 percent of an individual’s max heart rate. And you don’t need to stick to traditional cardio in order to achieve an EPOC effect. Several studies have shown that weight training with various types of equipment can also elicit elevated EPOC.  

How Many Calories Does The Afterburn Effect Really Use? 

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So, is the afterburn effect real? Yes, research can say with a fair amount of certainty that the afterburn effect is, in fact, a real thing your body does under the right circumstance. In one study, participants who cycled vigorously for 45 minutes burned roughly 190 calories more after exercise than on days when they didn’t work out at all. Another study conducted with those who had metabolic syndrome saw that EPOC also had significant positive effects in regulating their body’s consumption of calories. Meaning this type of training could be especially useful in combating certain health issues, like obesity and diabetes.

So if afterburn helps burn extra calories, can it also help you lose fat faster? Well, that’s where things become a little less definitive. This is because the ability of HIIT to “put you in fat-burning mode, rev up your metabolism and torch calories for 24 hours after exercise” is not as great as was once believed.

In one study on the subject, researchers from Colorado State University looked at the number of calories burned both during and after a bout of HIIT. The study’s subjects performed a HIIT workout that involved pedaling as fast as possible on a stationary bike for 30 seconds. The average increase in energy expenditure for the HIIT exercise was 225 calories. And that’s not just the calories burned after the workout. It’s the calories burned both during and after exercise.

In short, HIIT had no impact on resting metabolism when it was measured 23 hours after exercise. All of the calories burned came during and immediately (2-3 hours) after the workout itself. So, it might be a safer bet to assume that your body is not actively burning a higher amount of calories after a HIIT workout. Also, the extra calories that you may burn are in a more conservative margin than a lot of afterburn believers think.  

How Long Does The Afterburn Effect Last Post Workout? 

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Some research shows that the afterburn effect after a HIIT workout lasts for up to 24 hours. However, studies done using a metabolic chamber (a more accurate way of estimating post-exercise calorie expenditure) show that the afterburn effect lasts for just 2-3 hours.

In fact, most of the calories burned after exercise, even HIIT exercise, seem to come in the first hour. For instance, researchers from Arizona State University compared three different workouts performed on an exercise bike. Here’s what each workout looked like:

  1. HIIT (four 4-minute intervals at 95% peak heart rate, separated by 3 minutes of active recovery)
  2. Sprint interval training (six 30-second sprints separated by 4 minutes of active recovery)
  3. Steady-state cardio (30 minutes at 80% peak heart rate)

They found that energy expenditure in the three hours period after exercise was greater with sprint interval training (110 calories) compared to steady-state cardio (64 calories) and HIIT (83 calories).

However, most (around 70%) of those calories were burned in the first hour after exercise. By the third hour, the difference in post-exercise energy expenditure between the different workouts was less than five calories.

So, interval training did have a bigger afterburn effect than steady-state cardio. The workouts were also 5-7 minutes shorter. However, when you add up the total number of calories burned both during and after exercise, it was the steady-state workouts that delivered the best results.

Final Word On Afterburn

While the afterburn effect has been shown to actually exist, and it is most clearly triggered after a HIIT workout, the effects of afterburn don’t last as long as a lot of people wish they would. While a HIIT workout is a really time-efficient way to squeeze in a workout if you are looking to torch some extra calories, longer and moderate forms cardio are one of the best ways to do it. 

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Lesley George

Lesley is a content writer and community manager at Shape.
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