Does changing resistance on trainer affect FTP?


I changed the resistance on my Tacx blue motion dumb trainer because I was gearing out . I went from 2 to 3 but kept my 152 FTP.

I could feel that the workouts were getting really tough to finish (near impossible actually) eventhough I was much better outdoors. I just figured I wasn’t mentally tough enough for SSB LB2 !

Going into Build, I just did a ramp test and I failed miserably although I was feeling good and refreshed. I tested at 142

I’m still thinking i tested poorly, as logically the software bases it s calculations on inertia and what not and Watts are Watts, but I’m still praying real hard that it does alter things !

Yes, for “dumb” magnetic and fluid trainers with adjustable resistance, altering that resistance setting is likely to impact FTP test results. The power resistance curve of the trainer is likely different at each step, because that is part of the point of the change in the first place.

Assuming that you are using VirtualPower in TR, one that is based on a speed sensor, you will be getting different trainer resistance based on the setting, even if you are at the same rear wheel speed. This can only lead to problems if you alter settings. Typically, you want to test and train at the same setting.

The main time it would be “OK” to switch would be if you had a dedicated power meter that reported actual power, not just VirtualPower via the speed and estimated result.

Related reading:

Thanks a lot for yet another useful answer !

It,s reassuring, although a little frustrating that I can’t assess my improvement. Then again I could try a ramp test on my old setting to get a sense of it, but it seems a little brutal (and, again, I’d probably gear out)

And yes, sorry, I didn’t mention that I was using VP

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