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One of the main reasons why people exercise is that they want to burn calories to achieve their fitness goals. When we work out, we raise our heart rate and need more oxygen (VO2) than usual. After a workout, our heart and breathing rate don’t immediately switch from a high level back to a normal one. Instead, our body kicks into the post-workout recovery period, which involves several processes.
While our body is doing work to return to a resting state after a workout, did you know that the body continues burning calories long after the end of an exercise? This post-workout calorie burn is known as the “afterburn effect.”
What is Excess Post-Exercise Oxygen Consumption?
Excess Post-Exercise Oxygen Consumption (EPOC) is the technical term for the afterburn effect. EPOC, also referred to as oxygen debt, is the amount of oxygen required to return the body to the pre-exercise state. The body performs a number of tasks that are necessary to reach that resting level. These tasks include:
- Replenishment of oxygen stores
- Replenishment of ATP stores
- Replenishment of creatine stores
- Removal of lactic acid
- Reparation of muscle
- Lowering of body temperature
Sounds confusing? Let’s put it this way. During intense exercise, the body needs more oxygen than our usual breathing level. There is a gap between the demand for oxygen in the muscles, and the amount of oxygen delivered is called the “oxygen debt.”
To pay off that debt and restore balance, as well as return to a resting state, the body needs a couple of hours. In the time that it takes to do those tasks, our bodies consume more than 10 liters of extra oxygen, thus burning more calories post-workout. This is where the afterburn effect takes place.
How Long Does Afterburn Last After a Workout?
In a study published in the European Journal of Applied Physiology, it is suggested that the afterburn effect can last up to 72 hours. Another study demonstrated that the levels of post-exercise calorie burn could persist for up to 38 hours. However, one should keep in mind that the length of the afterburn effect depends on a lot of factors such as age, gender, muscle mass, training status, as well as the intensity and duration of your exercise.
People who are more fit are greater fat burners than untrained people. This is because more athletic people train at a greater intensity for a long time. They may have a higher EPOC than those who are untrained, however, they have fewer calories burned post-workout because their heart rate and blood pressure return to normal in a relatively short time. Meanwhile, exercise newbies need more time to restore their bodies to the natural state of rest.
Does Exercise Intensity Matter?
The afterburn effect isn’t just limited to high-intensity exercise; it also applies to aerobic exercise and resistance training. The level of intensity is an important factor in how many calories you burn post-workout.
The National Institute of Occupational Health in Norway conducted a study where participants who performed cardio exercise at a lower intensity had less EPOC than those who performed at higher intensities. Subjects who did 80 minutes of bicycling at 75% of the maximum amount of oxygen the body can use during exercise burned extra calories during the 10 1/2 period after the workout.
Another research demonstrated that the more intense the workout, the more energy expenditure it will take to return the body to a resting state.
Aside from exercise intensity, the duration also matters. Shorter EPOC is observed in exercises with lower intensity and shorter duration. On the other hand, significant EPOC can be observed in long workouts done at the highest intensity.
However, this doesn’t mean that you would need to punch in 2 hours or longer at the gym. While the duration of your workout session can increase EPOC, if the intensity of your exercise is high enough, you can do a shorter workout.
How To Maximize the Afterburn Effect With High-Intensity Interval Training (HIIT Workouts)
Exercise enthusiasts swear by the fat-burning, muscle-building abilities that a short high-intensity interval training (HIIT) session can provide than a lengthy moderate-intensity workout. HIIT is almost always mentioned when talking about the afterburn effect.
This is because HIIT workouts are short rounds of exercises done at the highest intensity broken up with equally short recovery periods, resulting in a higher EPOC than steady-state exercises such as stair climbing or walking.
A study published in the International Journal of Sports Nutrition and Exercise Metabolism found that a 30-minute Tabata training session burned just as many calories over a 24-hour period as a 5-minute steady-state session. Not only do you burn more calories with HIIT due to its higher intensity, but you also save time with it.
High-intensity workouts are also better at enhancing body composition. The more muscle you have, the more calories you’ll burn while at rest. You will also increase your VO2 max, which is the number that indicates how your body efficiently uses oxygen during exercise.
One should keep in mind though that since HIIT is an intense form of exercise as implied in its name, it is better to limit your sessions to three times a week to give your body adequate recovery time.
What Exercises Cause the Afterburn Effect?
While HIIT workouts may be the most efficient in inducing the post-exercise calorie burn, there are other workouts that can trigger it as well.
Cycling helps in burning extra calories after a workout as it combines lower body resistance training with cardiovascular endurance work.
Sprint interval workouts have been shown to aid with fat loss at an increased rate. You also get to increase your muscular strength and cardiovascular endurance when you do a sprint exercise. This is one of the most productive ways to trigger the afterburn effect.
Resistance exercise bouts combined with cardio exercises not only increase fat loss but also enhance calorie burn after workouts.
The afterburn effect is an additional energy expenditure that occurs after a workout. The excess post-exercise oxygen consumption can translate into an increased metabolism and more total calories burned, producing additional weight loss benefits that may help you achieve your fitness goals.
If you experience discomfort during exercise, it’s best to stop and seek the advice of a certified personal trainer.