Originally Posted by
gsa103
Chest mounted sensors like Garmin use an algorithm by FirstBeat that is within ~10% of lab metabolic measurements (the most accurate method). When you take into account all of the uncertainties of power meters.
The average power meter is accurate to ~2%. Assuming 0.22 metabolic efficiency, the caloric accuracy of a power meter is ~9%. That's not really any different than a good HRM based measurement.
https://www.dcrainmaker.com/2010/11/...on-garmin.html
There's an interesting statement at the end of the DC Rainmaker article:
"Finally, it should be pointed out that the overall philosophy of the team [Garmin Corporate] is/was to get folks using heart rate straps if they want accurate calorie metrics."
The entire pro peloton is using HRM metrics in addition to power meters, so clearly they feel there's some significant value to an HRM.
If you want a tool for training intervals, fine tuning performance, etc. Get a power meter.
If you want to measure integrated metabolic work, use an HRM.
Presumably the combination of HRM+power meter is the most accurate.
I'm not sure I follow your derivation if the 9% error in caloric estimate by power meter. If a reading can miss the true value by +/- 2%, then multiplying a constant times it like .22 will give results that are incorrect by the same relative amount 2%, not 9%. I am not saying the results can vary by 2%, because that would suggest precision while you are talking about accuracy. But the calculation would be the same for precision.