You’re correct, higher watts definitely would have elevated HR. If I went 150% of FTP that would be 465-475w which wouldn’t be doable and would lead to either a failed workout or rapidly decreasing watts. Since it’s been at least year or more since my last short/short type workout there was some experimentation with power output.
This was also my third consecutive VO2 workout, so I was carrying fatigue into it. And my garage was around 78° ambient—not ideal. Still felt like this was a quality session.
I’ve learned that for me, a good VO2 workout is indicative of hard breathing and significant RPE. High HR usually comes with that, but today was different.