Indoor Trainer Speed to Power?



cbjesseeNH

Member
Jun 10, 2005
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Sorry if this is old thinking, but it seems that if the speed vs power relationship is known for a trainer (as in http://web.archive.org/web/20040314125035/www.geocities.com/almost_fast/trainerpower/), then one should be able to capture speed with SRM, PT or Polar and calculate power.

Am I missing other major factors? One has to assume the speed vs power data are accurate.

Especially for Polar, which is reputed to suffer error with indoor trainers, this might be an error correction, calibration or replacement power calculation method for indoor trainer use.

Thanks for the comments.

BRET
 

dkrenik

Member
Dec 5, 2003
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cbjesseeNH said:
Sorry if this is old thinking, but it seems that if the speed vs power relationship is known for a trainer (as in http://web.archive.org/web/20040314125035/www.geocities.com/almost_fast/trainerpower/), then one should be able to capture speed with SRM, PT or Polar and calculate power.

True. If the speed vs. power relationship is known one may calculate power from speed on a trainer. The issue is that there are a number of variable s to contend with (changes in humidity, temp, etc) that will affect power calculations. Also, unless your trainer is specificaly called out on the url you reference you're still "guesstimating".

DK
 

robgreen

New Member
Aug 16, 2004
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you
dkrenik said:
True. If the speed vs. power relationship is known one may calculate power from speed on a trainer. The issue is that there are a number of variable s to contend with (changes in humidity, temp, etc) that will affect power calculations. Also, unless your trainer is specificaly called out on the url you reference you're still "guesstimating".

DK
Also, even if your model is on the chart, without testing several of the same model, there's no way to tell how much variation there is between one unit and the next for a particular trainer model. I just got a 1Up trainer and I'm curious about the variation since I don't have a power meter, and I wondre how accurate these power curves are to determine a rough figure of work done on the trainer.
 

squidwranglr

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Jul 25, 2004
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robgreen said:
I'm curious about the variation since I don't have a power meter, and I wondre how accurate these power curves are to determine a rough figure of work done on the trainer.
I have a Kurt Kinetic Road Machine trainer and a Polar S720 with the power unit. When I do indoor trainer rides, I collect both the Polar power data and the implied power based on the Kurt Kinetic Road Machine speed-to-power relationship (available both from their web site, as well as the aforementioned URL) and plot them on a chart. The Polar power unit definitely exhibits its ring/hub specific sensitivity and inaccuracy when on the trainer, so I go mostly by the implied power. Here are two of my workouts where you can see both power curves (in the power chart, the dark blue line is the trainer power and light blue is the Polar power):

http://www.employees.org/~bozceri/training/20050704T221058.05562.srd.html
http://www.employees.org/~bozceri/training/20050705T225650.07758.srd.html

Just for the sake of completeness, the Polar power does appear to be right on the money when used on the road, though:

http://www.employees.org/~bozceri/training/20050712T183833.09580.srd.html#distance

Berend