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While answering this question, I researched some formulas for energy expenditure when running. None of the formulas I found took into account the factor of exhaustion when calculating calories burned.

To explain what I mean: If you start running, you feel fresh, you know your running technique and you have the fine-motor-skills to use it.
And so you run for an hour, you get exhausted, your legs ache and feel heavy. With this exhaustion your fine-motor-skills decrease. Your technique is inferior compared to when you started.

As far as I can tell, that should have an impact on calorie expenditure, as inefficient technique should burn more calories. Why is this not adressed in most (if any) formulas on energy expenditure? Is the effect just this small? Is it too complicated? Maybe it is indirectly considered when using heart rate as a factor?

EDIT: I feel I might have narrowed the focus of this question by using a running example. I'm interested in the general impact of exhaustion on calories burned in all sports, including running, weight lifting, climbing etc.

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  • An interesting question, but would it burn more calories, as you would be moving slower? Although I see what you mean about the effort being more....
    – Tracy at 2bactive
    Commented Mar 31, 2014 at 11:05
  • okay, forget running for a moment. If I squat my last working set, and make it, I wouldn't have that compensatory effect, as squatting slower is actually more exhausting. That last set should burn more calories than the first.
    – user8119
    Commented Mar 31, 2014 at 11:07
  • Again the effort is definitely more, it would make a certain amount of Sense that you would burn more calories... But I'm not sure.... Does finding something harder mean more calories are required? You are doing the same thing after all. I will think about this for awhile do my own research and report back. It would be interesting to see other peoples answers too
    – Tracy at 2bactive
    Commented Mar 31, 2014 at 11:21
  • I'm suspecting form will suffer with growing exhaustion. Considering squats, the back may be unable to hold the bar right, you compensate by leaning backwards, changing the angle. Moment arms change, Some muscles must work harder and overall energy expenditure should rise.
    – user8119
    Commented Mar 31, 2014 at 11:24
  • You are assuming that all things remain equal. Yes, you may be recruiting other muscles, but that is because the intended muscles are not working to capacity. They are working less, while others are working more. There may be a negligible difference, but it's probably not a meaningful variance.
    – JohnP ♦
    Commented Mar 31, 2014 at 14:36

2 Answers 2

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I think the body will burn more calories (or at least, the same amount) during exhaustion. This is because the body is actually doing more work (thus, expending more energy) while in this state.

Although the body might not be moving as fast as it was or as intense, the whole body is firing on all its cinders, the heart is desperately working to keep up with the blood circulation, the lungs are overworking themselves to provide the body with the needed oxygen, and all the muscles are fighting to take as much energy as they can find.

As a result of this phenomenon, the entire body becomes stronger and its endurance is longer. A lot of calories ends up being burnt as well.

This is why a lot of marathon runners or those that partake in endurance sports have lean bodies.

I'll update this answer once supporting sources are found.

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  • Cool, any sources quantifying the raise in energy expenditure would be very much appreciated :)
    – user8119
    Commented Mar 31, 2014 at 13:58
  • @LarissaGodzilla I'll add them once I can find them :).
    – Kneel-Before-ZOD
    Commented Mar 31, 2014 at 14:02
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    I'd appreciate if whoever downvoted my answer provide a reason for the downvote. We're all here to learn.
    – Kneel-Before-ZOD
    Commented Mar 31, 2014 at 15:29
  • greater calorie burn goes along with higher heart rate.. Id assume in this state it would have similar results to HIIT, with EPOC burning calories after the workout is done as well.
    – user32213
    Commented Dec 7, 2020 at 15:34
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Interesting question!

My take on this: Inefficient technique will recruit more muscle to do the work and hence, will increase caloric expenditure. But I believe the intensity at which you are performing it matters too.

For example, if you’re running at 70% of your max aerobic capacity (VO2 max), you will definitely burn more calories than running at 30% VO2 max (just a rough figure to estimate exhaustion). Overall caloric expenditure will increase due to prolonged exercises but if you compare any specific time frame (say 10mins of running) when you hit exhaustion to before exhaustion, I dont think it will burn more calories.

Your body will signal for you to slow down at exhaustion as a way to protect itself. More muscles are recruited but are doing work at a low intensity. Let me know what you guys think!

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