The first time
we did those the instructions weren't super clear and we wound up sprinting them down the hills. Which mean that I ran close to marathon pace for four full hills. At one point our group of eight was down to three (guy #4 was puking in the bushes) which was just an all out sprint. It was basically marathon pace, uphill. No HRM back then, but pretty sure it was L4.
I wish this happened in more temperate times. I'd love to get a group together for that all out sprint up and down type of run again. Maybe in the fall. Type 2 fun.