Hi. Been tracking my rides on Xert for 2-3 years now. Got a BT yesterday when climbing outside - the first in a few weeks. Xert extracted the ride as 909pp 9.5hie 227tp. The PP is a little higher than I can put out. My current sig had been running with PP closer to 850w and HIE around 14. The TP is about right. So I used the advanced tab and refresh button to adjust the PP to 850w and this increased HIE to 14.6 giving the BT at 850 14.6 227. Are these 2 sigs equivalent in terms of effort to BT - I presume starting from a lower PP and dropping to the same TP over the same period means you have a larger HIE store? It gets a bit confusing even when you understand it 
2 Likes
I have been digging into better understanding of HIE recently, read forum thoroughly and listened to podcast about Fitness signature and my understanding was opposite. When one has high PP and high HIE, TP would be low, so for same TP and higher PP, HIE should be higher. At least it was my understanding. I asked for more info and explanation in topics HIE understanding if PP-TP=HIE is misunderstanding and sent question to xert support too, but did not get any answer from Scott yet - maybe he is occupied with exams or sick(hope not)?
1 Like
Hi Danny thanks for your response. Yes intuitivity PP-TP=HIE. But if you use the Advance tab and the Refresh button to move PP around for a given BT whilst keeping TP fixed you find as PP increases HIE falls. This has the effect of making the MPA curve fall more steeply (rapidly?) so that it reaches the same BT point (MPA=TP). I am then not sure whethe Xert considers that adjusted sig for the ride invalid (rather than an equivalnet alternative) as it will change it back to the original if you apply the Extract button. You can of course just save it. We need one of the Xert gurus input on this Armando
1 Like
Correct. Typically a given PP have a range of HIE values that generally accompany it (see this FAQ here), but how Xert is able to assign HIE and TP depends on the close interaction of MPA & Power. Generally very short, punchy BT’s have a very low maximal effort time (small circle on progression chart), so I tend not to trust them quite as much as a long effort where MPA gets brought down, or I spend lots of time at/near MPA - this means maximal effort time is longer (bigger circle on progression chart) and the extracted signature is likely a better representation of your fitness. Hope that makes sense.
Almost… remember that a BT point can be anywhere on the PD curve, not only at MPA = TP. But generally yes, decreasing HIE (or decreasing TP) will lead to a faster decay of MPA above TP. Generally HIE has a larger influence on efforts in the 30s-180s range, while TP has a larger influence on efforts exceeding 5 min.