“Following the workout, as your body recovers, your metabolism stays elevated so you’re continuing to burn more calories and more fat hours after the workout is over,” says the video at OrangetheoryFitness.com, an exercise program designed to boost “afterburn.”

How do you boost afterburn?

“Exercising at a high intensity or for a prolonged period of time at a moderate intensity can increase afterburn,” says Jenna Gillen, assistant professor of kinesiology and physical education at the University of Toronto. “But intensity has the most impact.”

Still, that impact is modest. For example, when men exercised for 80 minutes, afterburn was roughly twice as high when they switched from a lower to a higher intensity. But afterburn accounted for only about 6 percent of the total calories burned during and after the hardest workout.

“You’ll hear claims that you burn 40 to 50 percent more calories than you would at rest due to afterburn, but the effect is much more subtle,” says Gillen.

Afterburn does help explain why you can save time if you work out at a higher intensity

Gillen's team had men either cycle at moderate intensity for 50 minutes or do 20 minutes of high-intensity interval cycling (one-minute bouts alternating between hard and easy pedaling).

“They didn’t burn as many calories during the high-intensity interval training as when they did the longer, moderate-intensity exercise,” says Gillen. But their afterburn was about 100 calories higher after the high-intensity intervals.

“So over a 24-hour period, calorie burning was similar.”

The bottom line

“Afterburn is real,” says Gillen, “but its contribution to total calorie burn is overstated.”

Photo: KasparsGrinvald/stock.adobe.com.

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