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The afterburn effect: Myth or magic bullet?

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The term ‘afterburn effect’ comes up repeatedly in connection with high intensity training. For some, it’s a miracle cure for burning calories; others claim it has hardly any effect. To this day, afterburn effect has not been fully researched because of the complex interaction between the underlying processes and systems. But one thing is certain: we as Free Athletes benefit from the afterburn effect, which is why we briefly want to introduce you to its principles, what’s behind it, and what role it plays for you as Free Athletes.

Oxygen deficit and compensation

Among other things, our body needs oxygen to generate energy – the more work it must do or the more intense the stress on the body is, the more oxygen it needs. High intensity exercise such as Freeletics raises your pulse, respiratory rate and body temperature and your entire metabolismto a very high level over a very short period. The difference in metabolic activity, when compared to a resting state, is enormous.

It takes a few minutes after beginning a vigorous workout that your body is able to use as much oxygen from the air as it needs. Due to this time delay, an oxygen deficit has occured. This deficit will be compensated after training. Then, even more oxygen is absorbed, more than is actually needed to recover the deficit. You could say that the oxygen debt is being repaid with interest. This effect is called excess post-exercise oxygen consumption (EPOC).

Even when we are all rested after a training and our breathing has seemingly normalized, cellular respiration continues at full speed. Much energy is being used to regulate the many different systems back to their normal levels. In addition, our muscles remain in a heightened state of tension and regenerative process, such as the replenishment of glycogen and oxygen reserves. During this time, the repair of the micro traumatisms and increased protein synthesis, the depletion and recovery of lactate, the strengthening of the heart and vessels, the distribution of corresponding hormones, and many more processes, are all initiated. Together these require a large amount energy from our body, so prompting the so-called ‘afterburn effect.’

How long does the afterburn effect last?

The more intense the physical stress, the longer the body takes for these processes, or in other words: the intensity of the workout determines the duration of the subsequent afterburn effect. Although strictly speaking, an afterburn effect also occurs with low and medium intensity exercises, it is only really significant at a high intensity level.

A wide variety of measurements and studies keep reporting various results, ranging from 24 to 72 hours. Researchers agree on one thing: the afterburn effect reaches its climax in the first hour immediately after a workout; then it decreases exponentially. The further back the workout lies, the weaker the effect will be.

Should I try to regulate my training intensity with the afterburn effect in mind?

Of course, the after burn effect is a huge benefit of your training. However, it shouldn’t be a goal of your training – especially when you train with Freeletics Running. The only way to progress continuously and to improve your performance is a combination of different training intensities. The more progress you make the more intense you can train and the more calories you will burn.

How is the afterburn effect detected and measured?

Conclusions on the expenditure of energy may be drawn on the basis of the oxygen content in the exhaled air. Specifically: the lower the oxygen content and the higher the carbon dioxide and nitrogen content in the exhaled air, the more oxygen is burned during so-called cell respiration, which aims at generating energy. The content is measured via a breathing mask and a spirometry device, which the athlete wears during and after the workout. The result: with high intensity workouts, a high carbon dioxide content is shown not only during exertion, but also several hours later – a clear indication of increased cell and thus metabolic activity.

What exactly is the intensity of the afterburn effect?

To determine the afterburn effect accurately, the extent of energy expenditure during a training must be known. This, however, differs from athlete to athlete because everyone brings different physical conditions and fitness. Not to mention the differences in gender, age, hormonal conditions, metabolism and thus regeneration and nutrient utilization. Training conditions can also vary greatly from workout to workout: sleep, nutrition, stress, illnesses, hourly hormone composition and many more have a direct impact on performance, which can therefore vary from training to training. Since performance determines the intensity, the relative value of the afterburn effect cannot be determined exactly. The highest possible afterburn effect, however, can only be achieved if the athlete really goes to the limits of their performance during the workout.

A way to determine the effect would be the mentioned spiroergometry. These measurements are a very reliable means, but only very few Free Athletes are equipped with such a device – not to mention that wearing a breathing mask can be a nuisance when doing sports like Freeletics.

The afterburn effect - a over- or underestimated symptom?

It is estimated that the afterburn effect, depending on the intensity of the workout, may vary from approximately 5 to 20% of the energy consumed during training. Assuming a workout requires 500 kcal (measurable) and the athlete has reached the limits of performance (20%), the afterburn effect would amount to approximately 100kcal extra. This corresponds to about one banana. That might not sound like much, but the key difference is that these calories are obtained mainly from fatty acids.

Particularly for people with a low metabolism and the objective to burn fat, the afterburn effect triggered by high intensity workouts such as Freeletics Bodyweight workouts could be a deciding factor!

If you train with Freeletics Running, we also recommend you to do distance runs. They don’t lead to a significant afterburn effect but they train your fat metabolism meaning that your body optimizes its energy production and learns to generate energy from fatty acids – a process that it needs to make the after burn effect possible.

Afterburn effect and food intake after a workout - a contentious issue

To this day, researchers disagree on whether one should eat, and if so, what or how much should be consumed after a workout. The afterburn effect and its impact has not yet been fully researched. There are many different possibilities and opinions depending on the objective and the focus of an exercise program – the truth lies somewhere -between the two extremes and requires careful consideration.

With regard to optimal nutrient utilization, faster regeneration time and psychological well-being, we generally advice food intake immediately after a workout to provide your body with all the building blocks needed for the regeneration processes. As always, we recommend fresh and high-quality products, and the focus should be on proteins. We will soon being posting explanations on the differences and guidelines with respect to carbohydrate content, nutrient quality, and much more information on this exciting topic.