Did my FTP actually increase, or was it just the calibration?

Hello. I know I am suppose to calibrate my wheel on trainer, every time, 10-15 minutes into the ride, blah blah blah… but I never do (dumb move #1). Then, for no apparent reason, I calibrated it before my latest ramp test while the trainer was still ice-cold (dumb move #2). I got a spin down value of 15 seconds. Then I took my ramp test and improved my FTP by 4.5%, or 11 watts, which was 2 watts higher than my all time high earlier in the year, before I got injured and had to take some time off. I do feel fitter, and I was expecting an increase, but now I can’t shake the notion that I cooked the books by calibrating right before my test.

This evening, I did my first hard over-under workout with the new FTP. I calibrated again before starting the workout, because now I am paranoid. Got a spin down of 15 seconds again. As expected, the workout was very hard, but I did finish it without turning down the intensity or backpedaling. Then, out of curiosity, I calibrated at the end of the workout and got a spin down of 19 seconds. I figure I’ll just leave it there since that value was recorded when the trainer was warm.

So did my FTP actually increase, or am I calibration-doping? Also, what is calibration anyway? If I use a power meter and power match while training indoors, isn’t my power just being recorded from my power meter? Shouldn’t the power from my power meter be legit (which I do calibrate every time!) regardless of what I do (or fail to do) with my trainer?


  • A process where the trainer spins down from a known speed to another known speed. The time it takes to do that is used to “calibrate” the power data from the trainer. In the case of a wheel-on trainer, it is meant to handle the variables like tire stiffness, tire pressure, trainer roller pressure and system friction (bearings and such) to give you more accurate power data.
  • If you are using the trainer as your primary power data source, it is best to follow standard practice and calibrate after about a 10 minute warm up.
  • Yes and Yes. Using a power meter as your primary data source, along with PowerMatch effectively negates the need to calibrate the trainer.
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Ideally, yes. But just do it at a consistent time each workout. I do it first thing before I start the workout, so the trainer starts cold, but it’s consistently cold every time. Accuracy, not precision.


First Over/Under at a new FTP… you should barely finish

This probably isn’t best practice, and will leave you second guessing your FTP next time. Just get in the habit of calibrating when you calibrate your power meter and you’ll never have any questions.

This leads me to believe that you have no reason to worry. If you’re power was coming from a calibrated power meter that you calibrate every time, the power data is accurate.

In my opinion, yes! Nice work!

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Thanks guys! Great answers all around, especially because it was the answer I was hoping for! Sorry, should have led with the fact that I am using a power meter.

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