Stryd CP vs. rFTP | 80/20 Endurance

Stryd CP vs. rFTP

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  • #11516

    Hi there,

    I know there was just a recent post to not use the Stryd auto CP but the actually tested rFTP from a 20min test.
    However, I don’t care whether or not the zones line up as I run by the 80/20 zones anyways 🙂 and let Stryd do whatever it does. I find it actually quite interesting to just monitor the numbers, etc.

    What I do wonder about is the Stryd race predictor tool. Here an example:
    Stryd auto calc. CP: 297 watts
    Stryd Half Marathon target power: 278 watts or 94% of Stryd CP
    80/20 20min test rFTP: 289 watts (95% of 304 watts)

    What is your experience with the Stryd race target power predictor? It would make me try to run a HM at almost 96% or my rFTP (20 min test). The last time my CP in Stryd changed was when I ran the rFTP test, so the numbers are from exactly the same time.
    Do you think/know if it is realistic to run a HM at 96% of rFTP? Or do you think that the Stryd CP and therefore race target power totally overestimates my abilities? The target power at 94% using the rFTP from the 20min test would put me at 272 watts, which is 6 watts lower (I know it doesn’t sound like a lot but I feel it can be a lot over 13.1 miles).

    I just ran the RCI3 today in the early PM (after I the CRe10 in the morning) and had not issue to maintain very high Zone 3 for all four 8 minute intervals.

    Thanks for sharing your thoughts!

    Matt Fitzgerald

    I’d love to get more feedback from the community on this. I’m still learning. With my one-on-one clients I’ve seen its race predictions be creepily dead-on (meaning agreeing with my own assessments!) in some circumstances and off the mark in others. Clearly, the algorithms are good, but only as good as the data. Sufficient breadth and specificity are required.


    Yes, it would be nice if some experience could be shared. I find it quite interesting to estimate a power output off of historical data and a race course. I certainly understand that wind and other external factors can play a role but if it would be “creepily dead-on” it would give a really nice indication.
    How do you normally predict or prescribe target power/pace for races? Based on rFTP or Threshold Pace? If so, do you use a % of that power/pace?

    Matt Fitzgerald

    It’s mostly tacit knowledge, stored in subconscious areas of the brain. I’m talking about knowledge of the sport and also knowing the individual athlete. Obviously, attention to data plays a big role, but there is no system or method. Ask any decent coach how they knew what their athlete would do and (if they’re honest) they’ll say, “I just knew.”

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