On another thread there is a link to some recent videos by Stephen Seiler. In it, he reviews some prior studies on how HR, RPE, and VO2 evolve over the course of short-interval workouts of different structures. His takeaway is that equal work:recovery is generally not enough to get you above 90% of HRmax, but that 30/15 is. It depends on the work intensity, too, which tended to be around 120% of the 6-minute power. It was kind of interesting. Then I took a nap.
Side note: this weekend I learned that you can do all the fine-tuning of interval sessions you want, but you’ll still get your butt kicked if your bike handling skills aren’t there. Nothing makes you doubt your training like being passed by someone carrying an extra 30 pounds and wearing a parka.