Originally Posted by
njkayaker
I'd guess that the difference is mostly due to a difference in the time spent in the various HR zones.
As far as I've read, it's not very accurate. Except for the ones based on power measurements. (The ones based on HR should be better than without HR.)
Here's some info on how the Garmins do it (the Nodes aren't likely to be as sophisticated):
http://www.dcrainmaker.com/2010/11/h...on-garmin.html
Thanks, that link explains a lot. Riding the bike on the road yields approximately twice as much calories as doing it on the trainer; this corresponds to how the effort seemed to me. The Nodes must use more than just speed and distance. A quote from the article:
Their calculation uses user inputted variables including gender, height, weight and fitness class. It then combines this data with heart rate information from the ANT+ heart rate strap. Specifically, it evaluates the time between heart beats (beat to beat) to determine estimated MET (Metabolic Equivalent), which in turn is used determine actual work expenditure.
These are the factors, plus gender, you enter into the node (which is ANT+ compliant). One of the many outputs are the times spent in each zone.
Rich