Nothing magical about 110, but you want to be above your comfortable range and spinning as fast as you can sustain while doing max power. I’ve had some people do them at 105, not much lower than that. I typically have people do leg speed work for a while before these and that does seem to help. Cadence ramps, spin ups, etc.
Not more muscles; more contractions, increase venous return to force more blood volume into your heart to increase stroke volume out.
Try 10-20rpm higher than normal for you, there will be an upper limit at which you can’t push hard anymore so stay just below this. And it’s not about recruiting more motor units, one benefit is that it recruits less and that helps reduce the muscular fatigue you would normally experience. This is how people can do many sessions in a week.
Do you still take the view that the high cadence makes a significant difference in cardiac filling compared to freely/natural chosen cadence? That was my main takeaway from your vo2max series. Of course, reducing muscular fatigue is an argument as well.
Yes, that’s still my hypothesis (an original one I might add, in the spirit of Cog) and I’ve got enough data to be fairly confident in it, though there are some other potential parallel mechanisms at play which can’t be ruled out. The reduction in muscular fatigue is a nice benefit, and some would say the main benefit.
Thank you for the reply! These blocks really moved the needle for me. I love them.
Or alternatively, FTP (or critical metabolic threshold) is lower at the end of a high cadence high intensity interval session?
Higher cadence raises HR, breathing rate, and VO2 primarily because higher cadence requires more accessory muscle recruitment which costs more energy for the same power output.
Indeed, “high” cadence is dependent on the athlete’s freely-chosen cadence (FCC), and FCC will tend to be higher at greater workloads, which also explains why elite athletes tend to have higher FCC and appear to be more efficient at higher cadence, because their workloads are higher at the same relative intensity.
Training at higher cadences, insofar as it’s been studied, does not appear to additionally improve time-trial outomes, although it may improve metabolic efficiency when performing at higher FCC.
(for those who want to avoid twitter - you’re clearly smarter than I am 
- you can view the entire thread & links to references here: Cadence Affects Everything, and it Doesn’t Really Matter – Spare Cycles)
Vo2max workouts. Indoor or outdoor? Pro/cons? Indoor maybe better to go hard withour risk of external interference? outdoor maybe easier to go higher in cadence then indoor?
I think there are pros, cons, and personal preference.
Indoor as you said allows you to go all out and not think/worry about any interference.
Outdoor might allow a higher wattage (for those who have a lower indoor ftp). And might provide more distraction from the effort. 
I don’t think there is a wrong answer.
Yeah, I like to do same for 5-min VO2max intervals in erg mode and use cadence for easy “pretend hard” starts:
Something like this:
But this strategy is somewhat specific for 5-min intervals (at least for me):
Thank you for the advice! Achieved the goal of being able to do multiple workouts per week. Got the HR and breathing up etc.
One question that I have with this strategy: If the goal is to not fatigue the legs, enhance the load on the heart to be able to do more workouts, what about the heart? Is it unproblematic to do multiple of these in a short amount of time?
VO2 will also fatigue the heart… but based on what I’ve read, more people have legs as their limiting factor, not their heart. Hence the logic of preserving legs I think.
I’ve heard of cardiac issues a couple times, though none coached by us since we know what to look for, plus we make sure people are cleared by their docs for high intensity. Problems seem to occur when taking the efforts to silly extremes, not enough recovery, not enough food or sleep, or all of the above. Or someone who just jumped into it off the couch (me). Cardiac problems seem to indicate that you were either not healthy or well trained enough to begin with, or were ignoring myriad signs that you should have stopped a long while before.
tldr: if you’re watching the power progress, odds are decent that you’re recovering just fine. But regardless, if anything seems weird, stop immediately and go see a doctor.
Thanks to everyone who has chimed in to this thread. Hopefully I have learned some things to implement into my VO2 training.
So I have it right, I’ve summarised the thread into the following:
Enter VO2 max intervals with an eye on a higher than normal cadence with an eye to sustain the target watts - preferably higher.
Go deep each rep to replicate the effort and better the effort, but keep RPM up as the HR activation is what we are after with the Watts a compliment to that physiological affect.
Find a cadence/gear that allows you to achieve the above and go all out
Worry less about failing the Watt target and worry more about the HR
Do I have that right or have I missed something? Please correct me where I have erred
TIA
Not quite. Not so much the rate at which the heart is beating as the amount of work it’s doing. Your breathing is a better indicator that you’re doing it right than your HR.
Got 2 weeks / 4 quality VO2 days done. 4-6min intervals high cadence almost all out. Now on 3rd week my gf got the flu and I had a sore throat too but it seems to be passing. Pretty sure if I do high intensity I will be sick too I think I’ll just make this my rest week.
I was hoping to do a threshold / over-under block after this but is 2 weeks of VO2 enough or should I do some more VO2 / short power stuff first?
My heart rate is already a lot lower when doing endurance.
8 workouts in 2 weeks is probably plenty, especially if this is your first time with something like this.
HR being low could be stroke volume, but probably more likely fatigue at least during the block/immediately following. That said, it’s not uncommon for me to see lower HRs in endurance riding in the few weeks back after VO2 blocks.
I only did 2 workouts per week, but I managed to complete the 3rd week.
Did 5 x VO2 workouts and a 20min pr where I sprained something in my chest breathing so hard.
I hope it’s enough can’t imagine doing more than 2 of these a week.
I used to struggle holding 110rpm but it feels so much easier after switching to shorter cranks.
Started with 4x4min and ended with this, got 16min at over 90% heart rate.
6 will be OK especially in your first effort at that. Usually when I give 2 per week I give them back to back so you get a strong stimulus each week then recover from it. It works, not quite as well as the bigger overall load. I usually aim for 3x3 for most people, but it’s tough, for sure, especially with life stress and such.
2 weeks into your first ever 3 week VO2 block…
I’m almost done and have 2 hard workouts left! Today my description was “F my life”. It’s definitely a whole new stimulus and @kurt.braeckel has helped immensely.
