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Bonus Calories or Fitness Myth? The Truth About Afterburn

Bonus Calories or Fitness Myth? The Truth About Afterburn

Learn about afterburn and whether or not it can truly help you torch calories long after you’ve left the gym.

What is afterburn?
The afterburn effect has been intensely debated in the fitness and medical communities for over a century, with countless studies attempting to measure and explain the phenomenon. Afterburn, or excess post-exercise oxygen consumption (EPOC), refers to the period of increased oxygen uptake following exercise. It may last for hours or even longer than a day, depending on the type of exercise performed. During that time, one’s metabolism is believed to speed up, causing additional calories to burn. But some lingering questions have long teased scientists: exactly how many calories are we talking about? And can those bonus points contribute to weight loss?

Expert opinions vary since study results have conflicted due to factors like the weight, gender and training levels of participants. However, most reliable studies agree on one key point: there’s a relationship between exercise intensity and the amount of afterburn that people tend to experience. After a certain intensity level is reached, that relationship turns into a direct correlation, meaning the harder you work, the more you burn.

How do you know if you’ve reached the right level of intensity?
Research suggests that the target intensity level is around 50-70% of a person’s VO2max, or the maximum amount of oxygen used by an athlete while performing an activity. At around 70% VO2max, it’s generally too difficult to both breathe and carry on a conversation at the same time. That level of exertion is supported by the work of researchers from Appalachian State University and UNC Chapel Hill. Their methods, which account for many of the weaknesses of prior studies, also helped to shed new light on the age-old question of calorie burning potential.

Their study took place in a controlled environment called a metabolic chamber, or a room that automatically monitors the calories burned by those inside. Young male participants were asked to spend two 24-hour days in the chamber. On the first day, they performed the bare minimum of activities of daily living to measure their calorie expenditure at baseline. On the second day, they repeated their routine, but added a 45-minute session on a stationary bike. They cycled at about 70% VO2max and initially burned around 519 calories. Then, remarkably, over the next 14 hours, they continued to burn an additional 190 calories!

Planning your next workout
Numerous additional studies emphasize the importance of intensity level when aiming to increase afterburn. For example, other research demonstrates that it has a greater impact on calorie usage than the duration of a workout. In fact, one study attributed five times more EPOC to intensity level than both workout duration and total work performed. This is consistent with evidence showing longer afterburn periods following interval training. These rules apply to resistance training (i.e. dumbbells, weight machines, rock climbing) as well -- the higher the difficulty level, the greater the amount of afterburn.

So when it comes to planning your next cardio session, consider alternating between intense sprints and short bursts of moderate-intensity running, rather than jogging at a consistent pace over a longer period of time.

Medically reviewed in February 2019.

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