I had my cardio fitness measured on a treadmill, and it was as bad as I expected (never really done sport or exercise for their own sake). My fitness VO2max was just under 28 ml/kg/min in other words for each kg of body weight I can use up to 28 ml/min of oxygen when flat out. So multiply by 80 kg gives 2.24 litres/min of oxygen which equates to 11 calories a minute or 660 calories an hour. Subtract the 80 I would use while sedentary and my maximum exercise burn potential is a mere 580 calories an hour.

Of course to burn 580 I would be at 100% capacity, which I can only do for about 3 minutes. In the "fat burning zone" of 35-50% VO2max I would use 320 cals/hour (240 more than normal) or in the "endurance" zone 440 cals/hour (360 more than normal).

http://www.sport-fitness-advisor.com/VO2max.html and http://www.brianmac.co.uk/vo2max.htm explain more, and give tests you can do yourself to estimate your VO2max. This may be helpful in estimating calories burned more accurately.

I also read some test results comparing obese and lean subjects at 70% of VO2max on exercise machines and the 140 kg (300 lb) 50% fat people used 668 calories an hour on average compared to the 51 kg (115 lb) 23% fat people using 515 calories an hour. This makes sense to me as you don't get fitter as you get fatter so the work rate of the obese folks was a bit higher on account of their higher lean mass, but only 30% higher despite being 2.8 times the weight - so the ml/kg/min will be much lower in obese people whereas the equation in the gym machine or HRM probably assumes it's the same.

Hope this helps someone get a more accurate handle on their calorie burn.

Where did you get that measured Yarwell?

Interesting stats there!

I did the 1 mile walk test, got a low result then went on the treadmill at a local specialist sports store ( advanceperformance.co.uk - Peterborough or Cambridge in England).

Good stuff.

Thanks for posting. That jibes with all I've read-- that most people burn a max of about 10 calories/minute at 'full bore' cardio.

It sounds like you're not terribly unfit, but very normal.

It looks like even the very obese don't burn more than 11 calories/min. or so. So much for 1100 calories in an hour of Zumba. No wonder people stall. Burn 600 in a workout, 'eat back' 1100 to avoid 'starvation', repeat.