calories burned on machine v HR?????

Options
Hi everyone just wondering your thoughts on the accuracy of measuring calories from exercise, i always thought that the machines at the gym were supposed to OVER estimate calories burned. but it looks like they maybe UNDER estimating.... example. i spend 45mn on xtrainer (enter in my weight 52kg) and it tells me i burn abour 400cals but it says my heart rate on average is around 173 (this is about 90 Max HR) so i would think buy looking at heart rate calculators my calorie burn would be more than 400? what do you think?
thanks for your help and sorry if i didnt explain it very well ;)

Replies