Last week I did another one of my simple experiments to find the boundary between stable and unstable physiology. Some promote Critical Power tests, I just find it on the ride by riding around “FTP” without having to ride for some indeterminate amount of time.
Here is what my HR looks like when riding just above stable physiology:
just to make sure I push the power a little higher:
Yup, the separation between stable and unstable physiology is somewhere around 280-290W.
From Skiba’s Scientific Training for Endurance Athletes:
I’ve been doing this since 2017, its really not that hard to find with simple field testing.