As Marc writes in hin plans, the zones in his trainingsplans using rFTP and this is about 5% lower than the Stryd auto-calculated CP (Critical Power). So in Stryd I have a CP of 207W and today the plan (Maintenance Plan) says 5min @CV (Zone 4 = 213-248W). I ran 5min at 220W and this was more 5min “all out” than a speed I can hold for 30min. So I should really use the rFTP = 0.95*CP = 197W. But how should I do this? I think TrainingPeaks uses the CP or should I use rFTP in the settings 197W? But there is always the difference with Stryd. Has anyone a hint for me, how to do it right? Kind regards!
pkral, sorry if I’m repeating some things you have already read on the forums, but just want to set the stage.
Two problems with using Stryd’s SP:
1. There is no industry standard for what “critical power’ means. It could mean anything to multiple training systems. Stryd does not quantify CP anywhere on their website. They just say “Critical Power is the threshold at which the dominant type of fatigue your body experiences changes.”
There is a common understanding in the industry of CP in terms of CP5, CP10, CP20, CP30… where the number represents minutes. I wish Stryd would just come out and say “we use CP20.” But, I’m pretty sure that Stryd’s mystery CP is CP20.
80/20 uses CP30, we are very clear on this: peak 30 minute TT power. You should be able to take CP20 is approximately 95% of CP20 to get CP30.
2. CP is just a guess, and estimate. It won’t be accurate. The best test you can do is an actual CP20 or CP30 run and not rely on the Stryd estiamte.
If 95% of your Stryd estimated CP is 197, that seems to be consistent with your latest run. Zone 4 for 197 is 203 to 236 watts, so 220 watts is right in the middle of Zone 4.
Therefore, 197 seems like a good CP30 (rFTP) for you at this time, but I’d do a test your next rest week.
Thanks for your kind answer! This helps a lot and I will go with the 197W and test again. But low Zone 4 with around 203W seems much more affordable to me. From my previous results CP looks more likely CP20 than CP30.