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Archive for February, 2011

Metabolism rises for 14 hours after hard exercise

February 27th, 2011

Pretty cool study from David Nieman’s group at Appalachian State, just published online at Medicine & Science in Sports & Exercise. We’ve all heard the various theories about how exercise pumps up your metabolism so you’re burning extra calories throughout the day. The only problem is that attempts to measure this have produced all sorts of conflicting results, primarily because it’s such a pain to measure. You have to hook people up to complicated metabolic measuring equipment over and over, control for whatever random activities they do throughout the day, and so on.

This new study has two big strengths. One is a fancy, newly built “metabolic chamber” — basically a tiny room where everything that goes in and out is strictly controlled, including oxygen and carbon dioxide. Measuring the amounts of oxygen and CO2 going in and out (along with exact knowledge of the food going in and human wastes going out) allows the researchers to calculate exactly how many calories the subjects burn while they’re in the room.

And the second strength is that they were pretty hard-ass about the study protocol. The subjects (10 healthy young men) spent two 24-hour periods in the metabolic chamber: one where they did basically nothing, and the other where they did nothing except one 45-minute cycling session at about 70% VO2max:

At 8:00 am, subjects were sealed in the chamber and asked to stay in a seated position unless they needed to use the restroom or perform other necessary daily activities (e.g. washing hands, brushing teeth, etc.). Breakfast was served through an air lock passage at 9:00 am. On rest days, subjects remained in a seated position from breakfast until 12:30 pm when they were asked to get up and stretch for 2 minutes. On both rest and exercise days starting at 12:30 pm, subjects were asked to get up and stretch for 2 minutes every hour until 6:30 pm… Subjects were asked to remain in the seated position until 8:00 pm, at which point they were able to relax and lay down but not go to sleep. Bed time was at 10:30 pm, and subjects were asked to lie down even if they were not sleeping.

Hard core! Anyway, getting (finally) to the point: exercise boosted metabolism for the next 14 hours, burning an extra 190 calories in addition to the 519 calories burned by cycling (i.e. 37 percent extra). Note that it was vigorous exercise, which the researchers believe is important — some of the earlier studies that didn’t find any metabolic boost used more leisurely protocols (e.g. 50% VO2max). Here’s what the data looked like: