Basic Polar HRMs (probably others too) using OwnCal require weight and
gender input, suggesting a more complex algorithm than your Cateye. Top
of
the range Polar HRMs are more sophisticated again.

Given the indirect way HRMs measure energy consumption it doesn't seem
reasonable to assume that they are very accurate. See the following link
for further information.

http://www.howtobefit.com/ehr6.htm


Thanks for the input Michael and the link.....

I had wondered about the accuracy of these things. A cheap HRM watch I have
gives me roughly double the figure the cat-eye does (it responds to the
cat-eye's belt, so it's getting the same data). The route I do (daily at the
moment) is 8miles out and return... The out leg is a moderate climb (a bit
of a struggle for me) and I try to 'sprint' (says he tongue firmly in cheek)
as hard as I can back down on the return.... Conditions are such that I'm
often cycling uphill into the wind (and of course getting blown gently along
on the way down) I'm deliberately using a very heavy bike 'clonky' and have
even gone so far as to compensate for my own weight-loss by filling the
carrier with training weights... All up weight is 240lbs....

According to the cat-eye I burn 314 calories on the round trip; down from
345 in the past three weeks.... Seems like a very low figure to me.....