“Afterburn effect” is the colloquial term for a metabolic process known as excess postexercise oxygen consumption (EPOC), which kicks in after intense exercise. While it is integral to the body’s recovery process — helping regulate blood circulation, body temperature, lactate metabolism, and more — EPOC is perhaps best known for causing an increased postworkout calorie burn.
Learn how this metabolic boost works and what you can do to leverage it in your training. (For a deep dive into the science behind EPOC, head to “The Afterburn Effect: Excess Postexercise Oxygen Consumption.”)
Why does the afterburn effect occur?
Your cells run primarily on a fuel source called adenosine triphosphate (ATP), which your body produces from glucose and oxygen. All exercise requires ATP during a workout. But higher-intensity exercise can increase the demand for fuel after a workout.
Following a tough session, your body requires more oxygen to recover and return to baseline. Your metabolism elevates to meet this need (commonly referred to as oxygen debt), which in turn results in greater overall calorie expenditure.
How do I measure my EPOC?
It’s not easy. Specialized lab equipment is required to accurately gauge EPOC, which is measured in milliliters of oxygen per kilogram of body weight (ml-O2/kg) — and not in calories, as some people believe. Some fitness trackers estimate EPOC based on heart-rate data collected during exercise, but these devices vary widely in accuracy. Don’t worry, though — knowing your precise rate of oxygen use isn’t required to benefit from this effect.
What exercise routine creates the most EPOC?
While exercise type and duration are important, EPOC is closely tied to intensity. In fact, EPOC increases exponentially as intensity increases. In other words, the harder you train, the greater your EPOC will be.
Among cardio activities, high-intensity interval training (HIIT) and the even higher-intensity sprint interval training (SIT) result in the greatest EPOC. In the world of strength training, hypertrophy training appears to be the most impactful.
It’s important to note that these are more-advanced training modalities. As such, these intensities can be difficult to achieve: “Hard” effort is not necessarily synonymous with high intensity. Such high intensities also result in greater stress on your muscles and nervous system; this requires prioritizing adequate recovery to reconcile that stress.
Because of the higher cost on the body, these training styles might not be appropriate for newer exercisers or for anyone dealing with adrenal issues, extreme fatigue, or sluggishness.
What can I expect from an EPOC workout?
In terms of calorie burn, probably not much. One review of studies suggests that EPOC amounts to 6 to 15 percent of the energy expenditure of a workout session; if you do a 60-minute workout that burns 500 calories, you’d burn an extra 30 to 75 calories through EPOC in the hours following.
But even though this afterburn might seem negligible, workouts that maximize EPOC through high-intensity exercise and resistance training boast numerous other health and fitness benefits. In that regard, you can expect a significant return on your investment of time and energy from these modalities.
So then why should I care about EPOC?
You don’t have to care about it. It will not negatively affect your fitness pursuits if you never think about EPOC again. But if it helps to use it as a frame of reference, you can think about EPOC as a sign that your body has worked hard. The harder you train, the higher your EPOC — and the higher your EPOC, the greater your need to recover. That recovery might look like scheduling a rest day after a high-intensity session.
More important, aim for balance in your training so that bigger efforts don’t leave you feeling run-down or worn out. Incorporate cardio of varying intensities and a challenging strength-training routine, along with adequate nutrition, sleep, and stress management (bonus points if the activities you choose are ones you genuinely enjoy). This combination can ultimately make a bigger impact than trying to maximize EPOC and afterburn.
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