Breakthrough values don't match current fitness signature

Just finished an activity. Got a breakthrough and my peak power went up.

Something unexpected happened though, the fitness signature on my “home” page doesn’t match the breakthrough value that I just achieved. It’s about 50W higher (just got 1281 W breakthrough, and fitness signature shows 1324 W on the home screen).

If I look at the “power duration” plot in the activity the “fitness signature for this activity” and “current fitness signature” don’t match. This is unexpected because I literally just finished the activity.

What am I missing? Is the “current fitness signature” taking into account recovery that hasn’t happened yet?

Hi Brett,

Correct. In addition to the signature bump you get from the BT itself, you get a small, bonus increase in your signature that is added from the XSS generated from that activity. It’s usually relatively small/unnoticeable, and is just enough to keep your signature relatively stable on a day to day basis (until your next breakthrough, or your training load starts to decrease).

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I see. That takes into account the predicted effects of your current training load. In essence, without that “bonus” the signature would not take into account that the activity you just completed contributed to more fitness? Assuming stagnant training load I suppose there’s some kind of exponential decay (I think I heard that on one of the podcasts)?

The idea does seem to be a little of a slippery slope though because the XSS may have also contribute to fatigue and so the effective signature won’t be as high (I know MPA and signature don’t take into account fatigue, and other related effects like sleep and nutrition).

Does the system think, in this case, that my PP will be at 1324 W tomorrow, or is it a longer term projection?

I wish the math were published somewhere…that would clarify a lot of things for me.

Correct, and the decay is related to your Training/Recover Load constants in Account Settings. Other systems use 42/7 for their proggresion management charts, but Xert uses different training load/recovery load constants for each system (low, high, and peak), which is likely closer to reality, since the way athletes can recover from HIIT is not similar to how they can recover from LSD (other systems cannot account for this since they lump all training into one dimension).

That is meant to represent your ability now. Obviously there is fatigue that may prohibit you to perform at that level immediately, but very difficult to model how chronic fatigue affects your signature acutely.

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Thanks for the explanation. I appreciate it.