vinaur

My guess would be that they would measure the actual work you've done and add in your body temperature increase and maybe, somehow, how much heat you've released into the atmosphere.

I'd imagine it being done in a thermally isolated room and measuring the increase of the temperature of the atmosphere.

Oh and those meters in the gym just take the stats of your workout and use the formula derived from the data obtained above to calculate the calories you've burnt.

The reason why the meters would be so much off, is because every person's metabolism is different and the way you do exercises also affects your energy output

Once again this is only the way I would imagine doing it, so it might be, and probably is, incorrect.

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