Felt this was the best place to follow up on this line of conversation on the Zwift thread. I was doing some further thinking about this last night and would be interested in others thoughts.
I totally get that an effort that is really spikey will not be representative of a steady state effort. But I thought that largely, it was the other way around? The spikey power profile will actually result in a lower AP than steady state? That’s the whole point of NP, right, and the fact that any bursts above threshold will have a large detrimental effect and hence the ^2 power in the formula?
In this particular case, I also had a power drop out. Looking at the detailed power file, it lasted 8-9 seconds, and in AP terms that could be quite impactful. Looking at the before/after power numbers, and adding those back in (I wasn’t coasting), I’d actually get a further 1.6w increase in AP for that 20 min best had the dropout not occurred and the power actually output been fully captured.
Then, in terms of “spikiness”, I had a VI for the 20mins of 1.01. And for the whole ride, Zwift Power has me at 25+ minutes with AP of 272w and NP of 273w. So whilst this wasnt steady state, it hardly seems like the kind of crit race where you’re either full gas, or off the power entirely.
I set power curve pb’s all the way from 8 minutes to 25 minutes, and there was only a drop of 19w throughout those durations.
Lastly, you do have the challenge that I went into this 25 minute race “rested”, in so far as I hadnt done the standard 5min clearing effort immediately prior, so I can see there would be some anaerobic contribution to these numbers that a formal 20min test would often try and eliminate. That said, I did a separate ramp test 6 hours before, where i also set a lifetime best, so my legs were certainly not entirely rested and had done a chunk of work at higher power numbers (for me) … I set a lifetime best 5min power for example.
So, my question is, is the suggested zwift and trainingpeaks increase in FTP valid? Should I go with my ramp test result from yesterday of 253w, or take the ego massage of the 260/261w FTP (notified by TP and zwift respectively)?
Ultimately I know both a ramp test and a 20 minute test are simply attempts at approximations, so neither likely truly reflect my ability to hold steady state power for roughly 60 minutes, but from a subsequent training perspective, do people feel I should go with the lower or higher number?
The ramp test is the like for like comparison, although I was far from properly rested going into it, whereas the zwift race number is obviously the number the ego would like best. Ultimately, it’s only 7 or 8 watts, which is only a little over the error tolerance on my P2M anyway, so I’m probably splitting hairs! There’s a chunk of general power related testing questions embedded in this however.