Changing Signature Decay Method - recalculate progression or not?

I used Xert in the run-up to a long gravel event in April.
Once that was done, I changed my improvement rate to Maintenance & have settled back into what is a more realistic exercise pattern, with the limited hours I have in the week.
I have now set my improvement rate to ‘slow’ to try & encourage a gradual increase in fitness.

But, I don’t think that the Optimal signature decay method is particularly helpful for my current training pattern.

My training load was increasing in the run-up to the event as was my Threshold Power. There was a bit of a dip just before, as I had a week where I was ill & then I had a taper week.
You can see the event; the tallest purple line. Since then, my TP gradually decayed until I did some weekly short Crit races in Zwift; each time reaching a breakthrough & upping my TP.
Since then though, there has been a steady decay and then on a group Zwift ride yesterday I put in a hard effort which got me another breakthrough & put me back up to a more realistic TP.

My issue with all of this, is that as my TP naturally decays with the ‘optimal signature’ the workouts get easier. Then I do a breakthrough & the TP generally goes up by a large-ish amount (+27w TP yesterday and 7W PP, from memory).
I guess the argument is that I should be doing more regular breakthrough rides, but this is not really feasible so I was thinking of adjusting the decay signature to Slow and seeing how Xert reacts to this.

Would changing the decay to slow be a good idea in this scenario? And If I do this, do I need to ‘recalculate progression’? I think that this is not necessary, but am not sure. The exclamation mark & yellow box made me think I should ask the question, before just blindly pressing buttons! Thanks for any guidance.

You could certainly use the ‘Slow’ decay setting, this would be an appropriate use for it. After changing the setting, simply hit the SAVE button!

Excellent - it worked! Haha. Progression recalculation is almost never necessary.

Here’s my advice… If you want, you could have Xert re-analyze your activities since your breakthrough in mid-May by opening that activity, flagging it and immediately unflagging it (or by opening it and clicking the ‘Save’ button at the bottom of the page). Either way, Xert will recalculate all your activities since then using the Slow decay method, which should reduce the amount you see TP decay over that time.


Great, thanks!! I tried the option of saving the May breakthrough activity after changing the decay to slow and this seems to have done the trick, re-calculating the activities since then.
I’ll see how I get on with that going forward :+1:

Interesting. I’m coming towards the end of my main focus for this year and will be riding mainly for fun/fitness and a few events that I just fancy until October. I’ve set an TED for one of the events in October but only so I can go through the base/build/peak phases (I’ll be following Xata loosely rather than religously), I’m pretty maxed out on hours that I can ride and have switched improvement rate to maintenance after a couple of weeks at off season (needed a break). I’ve noticed that my TP drops quite a bit between rides (again , I’m using the default optimal setting) and although I have been getting breakthroughs, they only seem to take me back to where I was before the decay dragged my signature down.

Would slow decay make more sense in this situation? When and why should you use the different options? I’ve read the support post about the ‘magic setting’ but really I’m none the wiser as what is the best fit.

I’m far from an expert, but if you are doing workouts then as your signature decays, the workouts become correspondingly easier.
If the decay occurs faster than your actual fitness decay, then the workouts will be easier than they should be/need to be.
I don’t get much time to train, so when I do I don’t want to be working at an easier rate than would be ideal. This is why I have swapped to a small decay and will see where this gets me. The fact that when I do achieve a breakthrough, it puts me back to where I was (and I have been following a ‘maintenance’ improvement rate, leads me to believe that the decay is faster than my actual decay.

If you are not doing Xert workouts, then this probably doesn’t actually matter.

Quick & Dirty for decay methods:

  • No Decay - your signature (TP, HIE, & PP) is where Xert predicts it to be, based purely on your last BT & changes in training load(s): BT’s will be really, really hard to achieve. Best to use when doing very few all-out efforts (like a base period).

  • Small Decay - your signature is slightly below where Xert predicts it to be, based on your training. The longer since the last BT, the more “underestimated” the signature will be. Generally speaking, aim for a BT every ~8 weeks.

  • Optimal Decay - signature is below where Xert predicts it to be, based on your training. The longer since the last BT, the more “underestimated” the signature will be. Generally speaking, aim for a BT every ~4 weeks.

  • Aggressive Decay - signature will decay every day, regardless of training. Can be helpful for avoiding overestimation/inflation of signature. Only use this method if you are riding to the limit & getting BT’s very frequently (like once a week).


Thanks for that, given that I predominately ride longer distances at a steady pace I’ve set it to Slow Decay and will try for a breakthrough as suggested. I rarely get one whilst out riding naturally as I have to pace myself on the longer rides.

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