FTP drop

I had a breakthrough workout yesterday and Xert said I improved my fitness signature yesterday, yet my FTP dropped? I’ve seen this topic floated around before, but I didn’t really see a great explanation, hence this inquiry. Anyone know why / how that happens? It wasn’t a big drop, so I’m not super concerned, I’d just like to know how this works. Thanks!

You want to think of fitness signature as three vertical gauges, not absolute values. The numbers will rise and fall and not necessarily in unison. The relationship depends on the individual and how you well you are adapting to training load for each energy system along your power curve.
How often a rise or falls occurs will depend on the phase you are in, type of training you are doing (focus duration), and how often you challenge yourself and achieve BT events during workouts or other activities.
TP is most affected by the decay method setting. While optimal is the norm that setting also requires more frequent BT events or near BT’s to ward off declines.
A small decline is inevitable as you approach your TP ceiling during a training cycle. The number needs to decay to a point where you can successfully lift it back up or the prior number was too high. So in your case the algorithm detected a BT but the TP calculation was not as high as what you achieved in the past so it gets nudged down.

It may also help to view the type of BT event you had. You can post your BT workout by clicking on the title to view the activity, then click on the BT award icon to generate the report.

Extremely helpful, thank you!