Hi team,
First post here. Sorry it’s not a short one, but hopefully of interest.
I feel as though this is distinct from the issue of being able to generate less power indoors due to biomechanical and other factors, which has been discussed before.
We have a Kickr Core, purchased predominantly for my partner to use with a non-power meter equipped bike over the winter. She has been completing workouts on Zwift and Rouvy on erg mode, with zones set from a ramp test done on that trainer, and everything seems to check out for her in terms of the expected resistance and RPE for her sessions.
I use a 4iii crank arm and have my FTP set from a 20 minute outdoor test. All my current outdoor workouts (extensive threshold block, 12-20 minute intervals at 95-102%) are manageable at the expected level of intensity.
From time to time, I use the trainer when the weather is bad. I created a workout in Rouvy this morning to replicate my outdoor plan for the day, opener followed by 3x15 mins @ 100%, and set the Kickr to read power from my crank arm.
By halfway through the warmup, it was clear that erg mode was not settling down to the target power, no matter what I did to adjust my cadence. 190W target was requiring me to record 230-250W just to keep the pedals turning at a reasonable rate (85-95rpm. I would typically warm up spinning faster than this).
When it came to the first work interval of 330W, same problem, and I was cranking out 360W+ regardless of cadence, to meet the resistance of the trainer. After a few minutes I reduced the % effort on Rouvy to allow me to complete the workout as intended. The recorded average power for the intervals was down around 310W (94% FTP), at an RPE that I would normally associate with at least 100% FTP effort.
Questions then:
Is this basically unavoidable, as a result of the losses between the crank and trainer, if the crank is being used to display the power output?
In this case, I want 330W based on my experience of how that feels when recorded at the crank.
There is x% power loss between that measurement point, and the point of application of the resistance at the trainer. Say 10%.
The trainer applies the resistance at 330W, but the effect of that on me is that I now feel 330W + ~10% at the crank?
Am I onto something, or would it feel just as “hard” if I was using the Kickr as the power meter, assuming both devices are calibrated and within tolerance? (Full circle to power being lower indoors). If that’s the case I’ll need to design my indoor workouts to allow for this.
Interested to hear some thoughts.
Thanks!