HIE too low, threshold to high

I have just begun to use Xert to track my fitness and I have come across some issues concerning the calculation of my fitness signatures.

In general, it looks like the figures which Xert calculates for my HIE are too low and for my threshold are too high. Far into the season, when I am very fit I can produce 1200W for 1s, 440W for 180s, 360W for 480S and 300W for 1200s. So I am rather good at sprints and short distances compared to long distances. If I enter the figures for 1s, 180s and 1200s into the fitness signature calculator the signature that is calculated looks about right – 1201W/33,3kJ/273W: If I am really fit I can ride at 273W for almost an hour.

However, at the beginning of the season and in general I don‘t do a lot of short distance efforts and when I look at the activities table the HIE values are declining over the season my threshold on the other hand rises to above 300W. This is not realistic, since I would never be able to keep a wattage this high for over more than 30 minutes. So what I did was to unlock all activities and enter a fixed fitness signa ture in my account profile that seemed realistic to me for the beginning of the season after a winter in which I did no riding and recalculate all progression based on this: 950W/25kJ/245W. I also played around with different decay values but whatever the decay value, the HIE numbers still drop over the season and threshold is way too high.

Moreover, after not riding in the winter of 18/19 the first fitness signature in 2019 is totally off: 816/19/217 – these values seem to be far too low.

How can I extract mor realistic numbers? Thank you in advance! Konrad

p.s.: I have workout data from spring 2018 to this day. So the fixed signature in my account profile applies to my first workout in 2018.

Hi Konrad,

All fitness parameters will decay if they are not being used. Therefore, you will need to test them occasionally to keep the values updated. As PP begins to decrease below its true value, HIE will also decrease below the true value, and TP will be overestimated. However, these are just modeling artifacts - its difficult for the system to make predictions about your high intensity systems when they aren’t being tested frequently.
The best way to fix this is to aim for a breakthrough that will reset your fitness signature. You can do this during a group ride, a zwift ride/race, or by doing a standard 20 minute test. However, since you mentioned that PP/HIE and TP are not accurate, you may want to test some shorter (30s) and longer (8+ min) efforts. Hope this helps!

Thank you for the quick reply! So that means I have to do regular short duration “best efforts” in order to correctly keep track of my HIE and PP? I will try to incorporate these in my training then.

Exactly. Cheers