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. ...

12 comments:

Benjamin Espen said...

With the four minute rest in the experimental workout, you certainly don't save any time over just running. But if you did it tabata style, with a much shorter rest period, there would be.

Stephen Hsu said...

I'm guessing the 4 min rest doesn't contribute much to the overall calorie expenditure. If you did the 2.5 min of sprints tabata style you'd probably burn about the same number of calories.

gide07 said...

See BBC Horizon, if you haven't, http://www.youtube.com/watch?v=FZ_BGhA7SK8.


Calories burned per unit time is only one of many differences between HIT and whatever.

esmith said...

Assuming power output of 500 W (ballpark for a 30-second all-out sprint for an untrained but generally fit young male), for 150 seconds, volunteers directly produced 75 kJ of work, which, at the typical efficiency rate, equates to about 80 calories burned.

Since this is an anaerobic workout, glycogen is incompletely broken down, large quantities of lactate are produced, which are reconstituted back into glycogen after the interval. Since the process is not 100% efficient, losses equate into more calorie burn.

There are more subtle effects in the hours after the exercise (under the general heading of EPOC = Excess Post-exercise Oxygen Consumption), and I can't find numbers on glycogen-lactate-glycogen loop losses, but I'd guess that just the first two channels give you more than half of those 200 calories.

You can probably achieve the same result through weight lifting, it just takes a bit longer. 50 reps of bench press or 25 reps of squat with a 120-lb barbell per interval should give roughly the same calorie burn.

ben_g said...

Sprinting and powertifting both seem to have a great bang for their buck. I've been in my best shape ever with a combination of BJJ 3 times a week + a balanced high protein diet. Can't think of anything that doesn't get worked out through Jiu Jitsu, and it's more fun for me.

Benjamin Espen said...

I agree with you on the total time frame. I've been doing HIIT for several years now, and most of the workouts seem to end up in the 10 to 20 minute range.

esmith said...

Before civilization, there was no exercise, but life was very exercis-y in general. Hunter-gatherers tended to burn 1000 calories/day on physical activity just doing their usual stuff. And now it seems that our energy balance mechanisms somehow fail when we lose those 1000 calories and adopt sedentary lifestyles.

gide07 said...

That was my point e. The very idea that one would only be satisfied with hard science in nutrition and exercise is ridiculous if one believes that man is most fit for his anscestoral environment.

David Coughlin said...

I was into bike racing for a while. For 'aerobic' intervals, he started with a 3:1 work:rest ratio, with a five minute break between sets. So a typical workout might be 4x3:00/1:00, 6x2:00/0:40, 6x1:00/0:20, 6x0:30/0:10. The goal was to repeat and complete, go at an intensity where you could repeat at a work intensity-heart rate combination [but just barely]. It was like popping a balloon when you blew yourself up. Sometimes you wouldn't even be able to get your heart rate back up to your training level, no matter how hard you tried. I'm not sure what caused this, but this is my long way of getting around to 4:00 of rest between exertions is probably a complete-rest-period, to keep you from blowing up.

esmith said...

Well, you need to clear out the lactate out of the muscles and to normalize the pH. 4 min rest intervals should drop the levels by more than half and allow you to repeat the interval with close to original power. The protocol you describe wouldn't let you do that, as you said, you'll blow up.

One recent study found that one efficient HIIT protocol that produces good performance gains is to do 4 min of work followed by recovery till your heart rate falls to 65% of max. In practice, that works out to about 2 min after the first interval and longer after subsequent intervals.

Anonymous said...

What are the risks involved while doing BJJ?

Christoph Adami said...

I'm not sure if the following point has been discussed much. It may be that speed does not significantly affect calorie burn rate (even though my own experience, not quantitative, suggests that level of exertion does figure). But there is something to be said for faster speeds helping time management. I simply do not have the time to burn a fixed amount of time in 11 minutes per mile. I have to get a mile done in sub 8 minutes, or else I'm missing 20 minutes I can spend otherwise. If you have a tight schedule (read, family), 20 minutes count.

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