Calculated power curve accuracy - 1 hour

After performing an extended FTP test - I.E ride at FTP as long as you can to establish TTE. I found I exceeded what Xert calculates for 1 hour yet I didn’t get any alteration to my signature.

On further investigation I used the fitness signature calculation tool to see if I could force a more accurate signature. Inputting the 3 values and using my achieved 1 hour power, I found the calculated curve at the 1 hour duration is lower than the value I used to calculate the curve! Is this normal for Xert to do this? Or have I some errors causing me to get this strange result?

In case the image is too difficult to read - 343w for 3600 seconds results in a signature result of 328w for 1hour and a threshold of 335w.

That does seem weird. I was going to say that Xert sees TP as higher than your 60m MMP, or better said, they’re just not the same thing. Having said that, I would have thought the actual 1 hour on your curve would have been 343w.

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Very weird. Massive kudos to your FTP and being able to hold it for an hour

Beyond about the 40 minute power mark, the calculation makes some generic assumptions on how an athlete will experience longer term fatigue over that period. The assumptions are pretty generalized so may not reflect everyone the same. Since your HIE is atypically large, that also has some interesting effects on the calculation that affect the results. Your “Endurance Energy” (not currently calculated) is likely well above normal too which would enable you to sustain more than your TP for 60 minutes.

More to come in this as we work on a new signature model that should allow for accounting for individual differences at this end of the PD curve.

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