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Old 12-06-09, 07:07 AM   #1
RacerMike
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Have a power meter? Help me conduct an experiment.

So, I haven't bitten the bullet yet and bought a power meter, although it is on my short list. In the meantime, I've been using a site to record my training and they calculate an average power number based on the formula at the following site:

http://www.braydenwm.com/calburn.htm

If any has a power meter and would be willing to spend 5 minutes running the numbers from one of your rides against this formula and report comparisons back here, I'd be very grateful. Results in the form of something like:

Power meter watts: ###.##
Formula watts: ###.##

Also, if you know your VO2 max if you could report the formula result based on that and with a value of 0.

Thanks!
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Old 12-06-09, 02:42 PM   #2
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I am sure that the numbers the sheet returned for me are very exaggerated. I am not averaging 300 W, which is over 4 W/kg. I am not a very good cyclist, and another site told me closer to 200 W (which seems more realistic). So, I'm pretty sure the sheet doesn't work for me, which means it is not universally accurate.
While I am inclined to believe the numbers it reports to me, as they are very flattering, the methods used are not very reliable. Regressions of these types are all notoriously poor.
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Old 12-06-09, 03:59 PM   #3
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Ride 1: 92 minutes, 234w avg, 168bpm avg. formula: 294
Ride 2: 42 min, 159w avg, 148bpm avg. formula: 243

Ride 2 was the warmup for ride 1, a climbing race.

Conclusion: don't waste your time with this web site. Using HR to calculate power is incorrect. Their suggestion of using your bike computer's estimate of calories burned is no better. HR can't be used in this context as there is too much variability between individuals.

If you want to train with power, you need a real power meter. Or, depending on what you want to use the data for, you can use RPE.
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Old 12-06-09, 06:44 PM   #4
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Ride 1: 92 minutes, 234w avg, 168bpm avg. formula: 294
Ride 2: 42 min, 159w avg, 148bpm avg. formula: 243

Ride 2 was the warmup for ride 1, a climbing race.

Conclusion: don't waste your time with this web site. Using HR to calculate power is incorrect. Their suggestion of using your bike computer's estimate of calories burned is no better. HR can't be used in this context as there is too much variability between individuals.

If you want to train with power, you need a real power meter. Or, depending on what you want to use the data for, you can use RPE.
Thanks for taking the time to plug in some numbers. I'm looking into a quarq system as a gift to myself over the holidays.
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Old 12-06-09, 07:11 PM   #5
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Thanks for taking the time to plug in some numbers. I'm looking into a quarq system as a gift to myself over the holidays.
If you haven't already, get a copy of "Racing and Training with a Power Meter" by Coggan and Allen. You'll need it if you get the PM anyhow.

I normally suggest to prospective PM owners to buy the book and read it. If you finish the book by all the cool stuff you can do with a PM, you should get one. If you get bored and put the book down halfway through, then don't bother with the PM- it'll just be an expensive bike computer. There's nothing wrong with not being a power weenie. Some people are analytical about their riding, others just do it. Both are valid, and just doing it takes less time.

If you get the PM, then you'll also need a copy of the WKO+ software. Or you can use the open source GoldenCheetah. It's not quite as spiffy as WKO but it's close enough now (if you use a current developer's build that includes the performance monitor) and unlike WKO it runs on OSes besides Windows.
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