1. What intensity relative to FT are you riding these intervals at?
FT is 240W (no laughing ... I'm a lightweight!). These I do at 270W
2. What happens with the volume of other stuff, threshold tempo, L2?
Not much! I do these on the trainer, so I get my longer/hilly ride on the weekend, plus perhaps one other 2 hour "spin" ride. I usually do a block of 3, then a day or two off, then another one or two. Compared to 5 x 5's I find them much more manageable, but my understanding is that they are long enough to be working VO2 systems.
3. How many weeks before target races do you do vo2max workouts?
I don't race. I throw in a week or two of these to break up L4 work once in a while.
4. What sort of improvement gains do you see?
Hard to say. Power is on my Tacx Flow. But ... I have a couple of regular loops I do and am definitely getting faster .. whether it's these or my regular diet of L4, can't say. Will test FT again in a couple of weeks.
Subplot here is that I do hilly century/event rides, where the hills are short and sharp. I figure 4-5 minute intervals are near the top of the list of what I need to be working on.
B