When most of us think about exercise, we tend to think about the energy expenditure that particular exercise causes in a somewhat immediate sense. As in: ‘How many calories will I burn if I perform X exercise for an hour?’
Now don’t get me wrong – there isn’t anything inherently wrong with this train of thought.
After all, if your primary goal does revolve around weight loss, then you ultimately want to burn as much energy as possible. With that in mind, it’s certainly in your best interest to take into account the amount of energy you burn during exercise.
However, there is much more to this story than meets the eye.
And it revolves around what is known as the afterburn effect.
What is the Afterburn Effect?
If its name didn’t immediately give it way, the afterburn effect actually refers to a phenomenon that occurs to the human body after the completion of the exercise.
This phenomenon is also known as excess post-exercise oxygen consumption (or EPOC, for short), and it is integral to your ability to recover after exercise.
You see, during exercise, your body is placed under mechanical and metabolic stress. While this may not sound all that pleasant, this stress is actually a very good thing. This is because it is ultimately what forces your body to adapt, thus allowing it to become fitter and stronger in the process.
Now after exercise, the body needs to work hard to recover from this stress to return it to a pre-exercise state. This means it must:
- Replenish oxygen stores throughout the body
- Refill muscle stores of ATP and creatine
- Breakdown and remove lactic acid
- Shuttle nutrients and proteins to the muscle tissue
- Repair the mechanical damage induced to the muscle tissue
- Resynthesis and replenish muscle glycogen stores
And the kicker? Your body actually needs to use energy to perform these tasks.
This means that you also burn energy after you have completed exercising, and not just strictly during exercise.
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The Scientific Breakdown of the Afterburn Effect
At first glance, the afterburn effect seems pretty straightforward – and I admit that the basics principles are fairly simple. However, there are a few things we need to consider in greater detail when discussing this interesting occurrence.
Research has shown that the afterburn effect tends to peak about an hour after exercise, and last right up to 72 hours post-exercise (although 24-48 hours is most common). However, the magnitude and duration of the afterburn effect are heavily dictated by three key factors. These include:
- The type of exercise that you are performing (aerobic vs weight training)
- The intensity of your workout
- The duration of your workout
With this in mind, we will break down how the afterburn effect influences energy expenditure in accordance to our different exercise modalities.
Aerobic Exercise and the Afterburn Effect
When it comes to aerobic exercise, the afterburn effect typically increases with both duration and intensity – which makes sense. Given that if we train for longer and for harder, the body will be placed under more stress, and it will, therefore, take more time and effort to recover from the stress.
A very simple example of this comes from one of the first ever studies performed looking at the afterburn effect.
This study had people cycle at intensities of 30%, 50%, and 75% of their pre-determined VO2max for a grand total of 80 minutes. The afterburn effect was most pronounced in the 75% group, in which it lasted for over 10 hours and caused an extra 150 calories burned (Bahr, 1991).
Now this is all well and good – hell, 150 calories is 150 calories – but not all of us want to spend 80 minutes performing an aerobic activity.
Which is where high-intensity interval training (HIIT) enters the discussion.
HIIT Training and the Afterburn Effect
Research has shown that the afterburn effect of high intensity interval training is significantly larger than that induced by steady-state exercise, even despite a much lower training time.
In fact, recent research has shown that performing a simple HIIT protocol of 30s at 90% max speed followed by 120s light cycling, for a total duration of 45 minutes, can burn up to 300 calories more than low-intensity aerobic activity over a 24-hour period (Greer, 2015).
And let me tell you, that’s nothing to sneeze at.
In short, when it comes to aerobic activity, HIIT causes a much larger afterburn effect due to its much higher training intensity. Moreover, given that it takes up less time than traditional aerobic exercise, it can be considered the most effective aerobic exercise modality with this intent.
Weight Training and the Afterburn Effect
While weight training is markedly different to aerobic activity, the load and stress it places on the muscle tissue have also been shown to elicit a pretty substantial afterburn effect.
In fact, research has shown that on average, a single bout of weight training will result in an increase in energy expenditure for around 40 hours post-exercise. Moreover, this increase in energy expenditure tends to be about 10% greater than what would be ‘normal’ throughout this timeframe (Laforgia, 2006).
So, for example, if your normal metabolic rate is 1800 calories per day, you can expect to burn an additional 180 calories per day for the day or two after your weight training session.
Pretty amazing really!
It is also important to note that much like aerobic activity, exercise intensity also appears to have some impact on the afterburn effect within weight training. This means that using heavier loads (around 85% of your 1RM) will result in a higher energy expenditure post-exercise than lighter loads – suggesting a much more potent afterburn effect (Fatouros, 2009).
Maximizing the Afterburn Effect
After taking an objective look at the research, it appears to me that there are two key ways that we can go about maximizing the afterburn effect.
Ideally, we want to perform a couple of heavyweight training sessions per week.
This will place the muscle tissue under fairly significant load, resulting in a prolonged recovery period that will cause a substantial increase in energy expenditure for up to 2 days after exercise. This is absolutely imperative if your goal is to burn as much energy as possible.
In conjunction with this, I firmly believe that incorporating 2-3 sessions of HIIT into your training week will make a world of difference.
HIIT will place the body under a significant amount of metabolic load, complementing the mechanical and muscular stress elicited by strength training. With this in mind, the combination of these two factors creates the perfect environment for a potent afterburn effect.
Now, with all this in mind, if you are time poor and can only get in 2-3 total sessions per week, I would strongly recommend combining both modalities of training into the single session.
In this manner, I would commence your training session with a solid bout of weight training. Ideally, this would be comprised of 4-6 exercises performed using heavier loads, all of which should take around 40 minutes.
After this, I would recommend you move into 20-30 minutes of HIIT on your favourite exercise machine.
Simple and effective.
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Best Exercises for Afterburn Effect
Building on the above slightly, I also thought it would be valuable to discuss some of the best exercises we can use to enhance the afterburn effect – and interestingly, the same principals apply to both weight training and HIIT.
And that principal revolves around the use movements that require a lot of muscle mass.
For example, our weight-based exercise should be compound and multi-joint in nature. Think squats, deadlifts, lunges, presses, and rows. These movements offer the perfect option as they not only use they most amount of muscle mass, but also allow us to use the most amount of external load. As a result, this increases the mechanical stress placed on the muscle, increasing recovery demands.
Similarly, for our HIIT session, our best bet is to opt for exercise modalities that integrate both the upper and lower body, such as rowing, running, or even an assault bike. Again, by increasing the amount of muscle mass used, we can increase the amount of recovery needed.
The Perfect Afterburn Workout
Using the principals discussed above, I have put together what I believe to be the perfect afterburn workout. This workout uses both weight training and HIIT to place the body under a large amount of mechanical and metabolic stress, sending your energy expenditure through the roof.
In this scenario, ‘A’ and ‘B’ exercises should be a superset (performed back to back) to increase the metabolic stress associated with the weight training.
Its important to note that while this workout will certainly maximise the afterburn effect associated with training, it won’t be easy – so make sure that you are prepared to put in some work!
Take Home Message
The afterburn effect essentially describes the energy that the body burns to recover from an intense exercise session. It tends to increase with both exercise intensity and duration, and appears to be most effective in weight training and HIIT when compared to low intensity endurance activity.
As a result, I have put together what I believe to be the perfect afterburn workout, implementing both amazing training modalities to create the perfect environment to maximise post exercise energy expenditure.
So, give it a go and make sure to get back to us – we would love to hear how you found it!
Bahr, Roald, and Ole M. Sejersted. “Effect of intensity of exercise on excess postexercise O2 consumption.” Metabolism-Clinical and Experimental 40.8 (1991): 836-841.
Greer, Beau Kjerulf, et al. “EPOC comparison between isocaloric bouts of steady-state aerobic, intermittent aerobic, and resistance training.” Research quarterly for exercise and sport 86.2 (2015): 190-195.
Laforgia, Joseph, Robert T. Withers, and Christopher John Gore. “Effects of exercise intensity and duration on the excess post-exercise oxygen consumption.” Journal of sports sciences 24.12 (2006): 1247-1264.
Fatouros, Ioannis G., et al. “Intensity of resistance exercise determines adipokine and resting energy expenditure responses in overweight elderly individuals.” Diabetes care 32.12 (2009): 2161-2167.