Thresold Power doesn´t match 20 minute test

Hello everybody,

I have been using Xert for a while but I still have the doubt about the values shown as Threshold Power, this because my best 20 minutes is 255 watts but the TP calculated by Xert is 257 watts, then I feel that the proposed workouts are more intense than I can do.

On the other hand, when I generate a plan with Forecast AI, for example, to improve my watts in a 20 minutes test, the starting point (257 according to Xert) is my realistic target value in 4-6 months time.

How can I handle this power difference between “reality” and what Xert shows me as fitness signature?

Should I flag some activities in order not to increase my TP in fitness signature and thus manage values closer to what the 20 minutes test follows?

Thanks in advance!

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Hi @FJorquera ,

Thanks for posting… could you leave a breakthrough report (or a screenshot of the MPA chart) from your last 20 min test? And when was your last 20 min test?

Xert doesn’t look at your average 20 min power do determine your threshold power. Instead, Xert is looking at your real-time MPA, second by second, relative to your power output and using that to determine your fitness signature. It’s very possible to achieve Breakthroughs that confirm a higher threshold power, even if your avg 20 min power wasn’t as high as possible.

I suspect that the only way that your FTP (determined by taking ~95% of your 20 min avg power) would be equivalent to Xert’s calculated TP would be if you rode perfectly at your 20 min power for 20 minutes. Any surges (especially towards the end of your effort) will suggest a higher Threshold power from Xert than the 20 min avg power data would suggest.

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Hello @ManofSteele
Thank you very much for your reply.
I did the last 20 minutes test on the 3rd of February, here are the screenshots of the complete route and the test itself. After that test the TP values were reasonable (246 watts) with a bronze breakthrough.
The following week on route with friends, the last part was “race” mode and in that activity I got a gold breakthrough that increased my TP to 258 watts (I also attach the screenshots).

Additionally, on February 15th I did a 10 minutes effort which also resulted in a breakthrough (broze) which in a way confirmed the increase of my TP to 258 watts. In this case it was 10 minutes at 280 watts ((attached).

Thank you very much!

20 minutes test

Gold breakthrough

10 minutes effort

Hi Fernando, thanks for sharing! Good efforts!

Your 20 min effort almost perfectly matches my explanation given in another thread (here).

In short, Xert is seeing that at the tail end of your 20 minute effort, you still had the MPA (capacity) to put out your best/highest power effort for the entire effort. If your TP was lower (like ~240 W), then you wouldn’t be able to have such a powerful surge at the end. Other platforms are unable to pick up on this since they’re only looking at the average 20 min power. Check out the post linked above for my full explanation. :smiley:

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Hi @ManofSteele,
Thanks for your reply.
I just read the explanation in the other thread and it makes sense with my MPA chart.
So thank you very much for the answer. Now it’s clear to me.

Best regards!