How big is the afterburn effect?

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After intensive physical activity, your body burns ‘extra’ calories due to the so-called afterburn effect. But how many calories is it really?

WHAT IS THE AFTERBURN EFFECT?

After heavy physical exertion, your body undergoes all kinds of processes to return to the state of rest (homeostasis), including replenishing the stocks of oxygen, ATP, creatine and glycogen, removing the lactic acid, restoring hormone levels and the repair of muscle tissues. The energy it uses for these physiological processes is officially called Excess Post-Exercise Oxygen Consumptio, EPOC for short, more popularly known as the ‘afterburn’ or the afterburn effect.

HOW BIG IS IT?

The magnitude of the afterburn effect is often overestimated. Usually it is only 6-15% of the total calories burned during the activity i ] . You burn the most calories by far with the activity itself.

The exact size of the effect depends on a number of factors, in particular: the type of training (cardio or strength), the intensity, the duration, the gender of the athlete and his or her training status.

ENDURANCE TRAINING

A much-cited Norwegian study measured the EPOC of 80 minutes of cycling at a low (29% VO2 max) to moderate (75% VO2 max) intensity. Logically, the EPOC was strongest in people who had cycled at a moderate intensity. For them it lasted no less than ten and a half hours, but the number of calories burned as a result of the EPOC was only 150 kcal ii ] . We say ‘only’, because compared to 80 minutes of fairly intensive cycling, that is not very much.

HIIT

HIIT (High Intensity Internval Training) is often touted as a cardio form for bodybuilders because the sessions are short (but intense) and because they are said to trigger a major afterburn.

The latter, however, seems to be OK (or against it). For example, see a study that compared EPOC after half an hour of continuous running with half an hour of 70% VO2 max with an interval session, namely 20 sprints of 1 minute each at 105% VO2 max followed by 2 minutes of rest. The EPOC of the interval group was about 69 kcal iii ] . Although that was twice as much as that of the continuous group, it doesn’t help you much in terms of calories.

Another study compared a 25-minute HIIT session (4-3-4-3-4-3-4) at 95% of peak heart rate to half an hour of steady-state cardio at 85% of peak heart rate. In the three hours immediately after the cardio, an afterburn of an average of 64 kcal was measured, after the HIIT 83 kcal iv ] . Not a big difference, but it should be noted that it was fairly intensive cardio. By the way, 70% of those calories were measured in the first hour after training. Yet another study also shows that EPOC does not last more than two to three hours after an average HIIT workout v ] .

However, there are also two studies that suggest that the afterburn of HIIT, as well as that of regular cardio, is longer lasting: 22 vi ] to 24 hours vii ] . But even then it doesn’t seem to be a significant number of calories and most of them are burned in the hours immediately after the training. These studies also show that the difference in extra energy expenditure between regular cardio and HIIT, viewed over a whole day, is not very large. As many other studies do, as contained in a 2017 meta-analysis viii ] . However, HIIT sessions are shorter.

The latter is therefore the most important advantage of HIIT: the time savings. We are skeptical about other alleged benefits, at least from a bodybuilding perspective. While HIIT sessions are efficient for burning fat due to their short duration, their intensity can interfere with your strength training recovery during a heavy cut , just as long, less intense cardio sessions can. This does not mean that you should not do any cardio or HIIT during the cut. But now we are outside the scope of this article.

WEIGHT TRAINING

What about the EPOC in strength training? It is likely to be larger and longer lasting than those after cardio and HIIT. This is because strength training disrupts homeostasis more than aerobic training ix ] .

The size or duration of the EPOC depends on a number of factors. Thus, the more intense the training, the longer the EPOC lasts ix ] . In addition, metabolic strength training, such as circuit training, produces a greater EPOC than traditional strength training with long rest periods between sets and exercises x ] . Training status also plays a role: advanced people are likely to recover faster from strength training than beginners x ] .

But how many calories is the EPOC of strength training, on average? According to a 2012 study, an hour of traditional strength training (8 exercises x 4 sets to muscle failure, 1-2 minutes of rest between sets) yields a 99 kcal afterburn (measured 22 hours after training). Which is relatively little if you compare it with the high-intensity training protocol from that same study, which worked with a kind of rest-pause sets until muscle failure. This training produced no less than 452 kcal of EPOC up to 22 hours after the training.

Another study shows us the difference in total energy expenditure between a strength training session of 9 sets (25 minutes) and 27 sets (66 minutes), namely ~235 kcal versus ~662 kcal xi ] . Remarkably enough, the afterburn was about the same in both cases, namely ~95 kcal. Apparently the training volume has relatively little influence on the size of the afterburn.

Finally, according to a scientific review, the afterburn from strength training can last quite a long time (15 to 38 hours) and amounts to 9 to 11% of the basal metabolic rate xii ] . So if that metabolism is 2000 kcal, you will burn an extra 200 kcal in EPOC after training. That is double the 95 kcal from just now, but the training protocols in the studies examined were often not very realistic in terms of intensity and/or volume.

In short, metabolic or very intensive strength training produces quite a large EPOC, but with regular strength training with a modal relative intensity (1-3 RIR) and normal rest times (1-3 minutes), the afterburn may not exceed 100 kcal.

As a bodybuilder, you probably mainly do regular strength training, as that is the most effective training style for muscle growth. So its EPOC is quite small – not much more than cardio and HIIT.

CONCLUSION AND PRACTICAL APPLICATION

EPOC or afterburn exists, but the effect is not as great as often thought or claimed: it usually amounts to only 6-15% of the total number of calories burned during the activity.

If you calculate your daily calorie consumption, for example by means of a calorie app, in many cases you do not even have to count the EPOC. This is all the more so because for an accurate calculation of the energy consumption of a certain activity you would have to subtract the energy consumption at rest. After all, if you do cardio for half an hour, for example, you won’t burn the calories you would burn if you had been sitting on the couch for half an hour (although of course there are not very many). So you can in fact cross out the EPOC against that.

The EPOC of regular, hypertrophy-oriented strength training is also not very large: an average of 100 kcal. These calories, spent mainly on (muscle) recovery, count on at the calorie consumption of your strength, you here can calculate. If you ‘re bulking, you’ll also eat some extra calories to facilitate muscle growth: aim for 10-15% of your maintenance level (5-10% for a lean bulk). If your maintenance is 2000 kcal, you eat 200-300 kcal extra (50-100 kcal in a lean bulk).

FINALLY

To lose fat you have to create an energy deficit over a longer period of time. You do this in the first place by means of a calorie-restricted diet (with high protein intake ).

Cardio or HIIT are an optional addition. However, the afterburn that arises, as with strength training, is so small that it will not make a substantial contribution to your fat loss.

REFERENCES

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