# Impact of cardio-exercise duration on burned calories

I've used a calorie calculator some time ago that had two different options for running.

• Running
• Running (less than 10 minutes)

I can only guess wildly. Maybe because the body burns energy stored in the muscles first and after a certain amount of time the body starts to refill them, which increases the energy needed.

Are there differences in the way the body burns calories after a specific amount of time?

Or asked in another way: Is there a difference between running for 3x10 minutes with pauses in between or running 30 minutes in one go (assuming all other conditions, pace, total distance, etc, the same).

• This question reminded me of that calculator. I've never used that specific calculator again, if necessary I will try to find it anyway. (But maybe that's not needed) Sep 17, 2013 at 14:50
• Are you sure that it was less than 10 minutes of exercise, and not less than 10 minutes per mile? If you run at a given pace, there is no magical shift in metabolism that occurs at 10 minutes. And no, there isn't going to be a real difference between 3x10 minutes at X pace and 30 minutes at X pace. The only reason to do that would be fitness (i.e. you could run 7 minute miles in 3x10 min segments with 1 minute rest, but you couldn't run 30 minutes straight at 7 minute miles)
– JohnP
Sep 17, 2013 at 20:24
• I tried to find said calculator and only found calculators that had "Running / Walking (running part less than 10min)" as an option, I might as well confused that. And of course, I would accept a no as an answer, too. Sep 17, 2013 at 20:46

I believe that the calculator was probably referring to running < 10 minute miles or similar, rather than less than 10 minutes.

Running at a given pace will have the same caloric burn, no matter how you slice it up. If you run for 30 minutes at 7 miles an hour in one shot, you will burn the same amount of calories as if you ran 3 10 minute segments at 7 miles per hour.

Where it might make a difference is in your own personal fitness. If you cannot run 30 minutes straight at a given pace, but you could run at that pace for 3 smaller segments of time, then you can get the increased calorie burn from the higher pace. This is one of the theories that HIIT is founded on.

But overall, the amount of time spent at a given intensity will result in basically the same calorie expenditure despite how it is apportioned.

• "Running at a given pace will have the same caloric burn, no matter how you slice it up." I think this statement is non-trivial. Are you sure about it? Sep 18, 2013 at 19:44
• @zero-divisor 100%? no. Do I think its an exact match? Probably also no, but I think the difference is negligible (Within 10-15 calories). I think the variation would be mostly in the fact that there would be more variance in pacing for the longer run unless you're on a treadmill. But overall, if you spend 30 minutes at a given pace, you will basically burn the same calories as 3 10 minute segments at the same given pace.
– JohnP
Sep 20, 2013 at 4:18
• Are you sure the difference ist negligible? I think this is completely non-trivial as well. For instance, the fuel consumption of a car on the first miles is a lot higher than after the car has warmed up. Couldn't it be the case that the body behaves similarly? Sep 20, 2013 at 5:51
• @zero-divisor - even if it does, that first 10 minutes would be the same if it's 30 min continuous vs. chopped apart. Now, if you go to the extremes and completely cool down between each 10 minute portion, then I suppose there could be some difference. But even a car, if you drive it until warm, shut it off for 5 minutes, it's still "warm" from the previous drive. Same same. I've spent a few days looking around, and I can't find anything that refutes this. If the speed/effort is the same for 30 vs 3x10, and thus the distance, calories should be basically equivalent.
– JohnP
Sep 24, 2013 at 16:52

As long as your total duration is the same, the outcome, whether it is increases in aerobic fitness or caloric expenditure, should not matter. Both ACSM and USDHHS recommend 150 minutes of aerobic activity per week divided into bouts of at least 10 minutes. (running is vigorous activity, so USDHHS says you can get away with 75minutes/wk and ACSM says 20min 3x/wk)

Additional info, as long as you are running, you can run the same distance with any speed and burn almost the same number of calories. Same with walking. (but running burns more calories than walking per unit of distance) However, keep in mind that aerobic fitness is more important for your health than calories/body fat%, so the faster you can run, the better (because increases in aerobic fitness is highly related to your activity intensity).