My HIE increased while FTP decreased. Why?

I had a breakthrough today and my HIE signature increased by 1.9 kj. My FTP decreased by three points, almost 1%

Is this normal?

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Yes. Xert’s wizards can explain why, but I think that increasing you HIE is very good. And a 3 point drop is really nothing, taken the amount of calculations and margins of error…

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It just seems odd that having a breakthrough and a 20% increase in HIE can also have a decrease in FTP. I’m not worried about the FTP drop, I just want to understand why.

Does this help: Understanding direction of changes to TP and HIE

And it not FTP :joy:


It’s a regression algorithm that adjusts your signature variables to best match your max efforts. Not so simple to untangle.


How did you achieve your breakthrough?

The way I look at it is that the two values stack on top of each other.
We are often stuck on the idea of equating FTP to performance, but things are more complex than that.
So if FTP is power you can sustain for 1hr or longer and HIE is the amount of work you can do above that threshold you can breakthrough by exceeding either one of these.

You can get a breakthrough by going 101% for an hour or you can punch thru your PP in 20s. In the first case it’s the result of increased FTP (and your power curve will go up on its tail end, >20m) in the latter your PD curve will grow on the short duration side. In either scenarios you have exceeded your previous performance.

With this approach, people training for ultra endurance and for cyclocross or crits can both achieve breakthrough, which simply means exceeding your previous performance, not necessarily increase FTP.

Their algorithm tries to find the best fit for your power duration curve and so you may end up seeing a negative adjustment in FTP when HIE is going up, and vice versa.

Hope this helps


That’s exactly what I needed to hear. I was doing short, explosive, intervals. I should see an improvement on longer efforts where that increased HIE will come into play. Thanks!

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