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Sunday, January 06, 2013

Sprints, interval training and energy expenditure

I've read studies in the past that found jogging or running at a moderate pace burns calories at a rate of about 100 calories per mile. This rate of energy expenditure depends on bodyweight, but only weakly on the actual running speed. Thus if you run, e.g., 2 miles you probably burned about 200 calories (depending on how big you are), whether you ran at 7 minute pace or 11 minute pace (i.e., you covered the distance in 14 minutes or 22 minutes).

However, from personal experience it seems that sprinting increases the rate of calorie consumption per unit distance significantly. The study below is the first I've seen showing this kind of nonlinear dependence of energy consumption as a function of level of exertion. Note, some of the 200 calories resulting from 2.5 minutes of sprinting is consumed during post-exercise recovery, due to elevated metabolism.

See also Tabata or High Intensity Interval Training (HIIT).
American Physiological Society : ... the men then checked in to a research facility at the University of Colorado Anschultz Medical Campus that was outfitted much like a typical hospital room. However, this room was completely enclosed, with air intake and exhaust regulated and equipment installed to analyze oxygen, carbon dioxide, and water content. Based on the results of this analysis, the researchers could determine how many calories the volunteers burned while each stayed in the room.

For two days, each volunteer lived in the room, continuing to eat the prescribed diet and spending the majority of their time in sedentary activities, such as watching movies or using a computer. However, on one of the days, they engaged in a sprint interval workout that involved pedaling as fast as possible on a stationary bicycle in the room that was set at a high resistance for five 30-second periods, each separated by four-minute periods of recovery in which they pedaled slowly with very little resistance. During the intense, 30-second bouts, the researchers coached the volunteers over an intercom system, encouraging them to give 100 percent effort.

Analyzing results from the room calorimeter system showed that the volunteers burned an average of an extra 200 calories on the sprint interval workout day, despite spending just 2.5 minutes engaged in hard exercise. ...

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