Originally Posted by Racer Ex

That's the difference between the "no chain" feel of a peak and the "wow, this hard but I must be putting out some wattage here...nope" feeling when you're falling off the peak.

Both tend to show a lower heart rate relative to PE. Aside from the "yesterday's news" effect.

Which is why racing on a HRM is, for me, a bad option.

And other than the first 10 minutes or so of a TT, my PM is pretty much a black box flight recorder to be examined later too. But the PM is a huge training aid, and HR data is good stuff to review.