Hi, I’m new to Xert and still trying to understand the concepts. Xert initially estimated my fitness signature from importing three months of training from Strava. The initial estimate of TP seemed to be too high to me (it was 301 W where I would estimate it to be rather around 265 W), but after playing a little with the decay method (I recently had to interrupt training for three weeks due to Covid infection) it seemed more realistic to me.
I did some training now and yesterday, in an indoor ride, I achieved a breakthrough with a significantly improved PP (HIE also improved). Honestly, I think that the previous PP estimate was simply not realistic because the three months of imported data did not contain any serious sprinting efforts as I focused more on riding around threshold power during the summer. While I think that my new PP value is more realistic, at the same time Xert now estimates my TP almost 20 W lower than before achieving this breakthrough. While the new estimate of 255 W might not be totally out of range (though most likely at the lower end of the realistic range), I’m trying to understand how increasing my PP can degrade my TP that much.
As mentioned, I’m still trying to understand the science behind Xert and would love to see an explanation for that.
Xert’s signature algorithm analyzes maximal efforts all along your power curve to establish PP, HIE, and TP values.
If your imported history lacked a wide range of max effort data points you can ride the standard Ftiness Test workout indoors in Slope mode to validate your signature. Or generate a simiilar effort outdoors. I.e. two max sprints (7-10 secs) with full rest-in-between (RIB), then four escalating intervals >TP with short RIBs until you reach a complete failure point on the final interval.
Once your signature is dialed in your normal riding activities should suffice for signature adjustments as long as they include occasional maximal efforts at various points on your curve.
At a high level, there is a link between PP and HIE, which is your capacity to do work above threshold (kind of anaerobic capacity even if Xert doesn’t claim to model physiology)… then, for a given max effort, the more Xert assumes you have relied on anaerobic capacity (HIE), the less it assumes you rely on aerobic capacity (TP) and vice versa. Before having an accurate PP, Xert would have been underestimating PP and HIE… I guess your HIE also increased quite a bit? And overestimating TP (which you said in your post)
This article and chart can be useful for checking your signature too.
In general, the more max efforts you have of various durations (doesn’t have to be constant max efforts to failure, but makes a difference if BT comes after 5 sec, 30 sec, 60 sec, 5 min, 20 min etc) the more accurate your signature will be
