Exercise Afterburn? Intensity May Be Key
Depending on whom you ask, the answer to this question is either one of the great myths of exercise or one of the great unappreciated truths: Is there an afterburn effect from a workout?
The latest study comes in a recent paper in the journal Medicine & Science in Sports & Exercise. Its lead author, Amy A. Knab of Appalachian State University, says it trumps studies that preceded it because of its careful design. And the results are good news — sort of.
Dr. Knab and her colleagues recruited 10 men, ages 22 to 33, who agreed to spend two periods of 24 hours each in a metabolic chamber, a small room that measures the calories people burn while they are inside. The men were not all athletes, but they did have to be able to ride a bike vigorously.
On the first visit to the chamber, the subjects had to stay perfectly still, sitting in a chair and moving only to eat meals, which were sent in through an air lock. In the afternoon, they were permitted a two-minute stretch every hour. Bedtime was 10:30 p.m. At 6:30 the next morning, the subjects were awakened and allowed to leave. They burned, on average, 2,400 calories on this totally sedentary day.
The second visit to the chamber came two days later. Everything was the same, with one exception. At 11 a.m., the subjects rode a stationary bicycle at a high intensity for 45 minutes.
The exercise itself burned about 420 calories, Dr. Knab and her colleagues reported. But what was most interesting was the calories burned afterward. Over the next 14 hours, the men burned an extra 190 calories, increasing the total calories burned by 37 percent.
“We were surprised,” Dr. Knab said. She thought there might be extra calories burned, but she did not expect so many, nor did she expect the effect to last so long.
She suspects one reason she saw such a pronounced effect was that the exercise was so intense. The subjects had had to cycle at 70 percent of their so-called VO2 max, the maximum amount of oxygen a person’s body can take in during exercise — an effort that made them breathe too heavily to carry on a conversation. And they had to keep it up for 45 minutes.
Read more about Workout Afterburn at:
http://www.nytimes.com/2011/04/19/health/nutrition/19best.html?_r=2&src=tptw
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