Keep in mind that “all out” is likely subjective to the context.
Point being that you need to consider the whole effort / workout before assuming All Out = Max Sprint Effort or similar.
Agree with this! I was thinking along the lines of 7 x 30sec but if you’re 20 min in you’re likely feeling like you’re in “all-out” territory.
Probably easier just to express it in terms of in-the-moment RPE.
Or, if doing 30/15s, an assessment of how near you are to needing to vomit into the plastic bucket.
Nice tip. This is what I do, too. It makes an enormous difference. You rest slightly less, but the odds of not being able to finish due to sharp resistance change go down drastically. You guys should add this tip to the texts in 30-30 workouts.
For sure @GoLongThenGoHome , it all depends on how hard you push your body. Your comment on 30x30s being a good intro to VO2max workouts is a good one.
Now I wonder the difference between 30x30s or 40x20s metabolically. Maybe there’s a study out there already. Wonder which has more w/kg for your buck. I guess either one works fine if you execute them properly.
Ah thanks, I had no idea!
The more well-trained you are, the less effective 30/30s will be, because the recovery is pretty much entirely aerobic. Get too good at recovering and your body will be spending too much time below VO2 Max.
40/20s or 30/15s give a better balance of effort to recovery to keep you in the right state of hideous discomfort for longer.
The silver lining for 30/30s is you can go a bit harder on the efforts, and so they can be good if you’re using them more race-specifically for Anaerobic Capacity.
FYPFY
I hedged my bets. 
I know in the US abbrevations are common…just they dont always translate elsewhere…I dont know what this one is???
Fixed Your Post For You
It’s likely 40/20 will have higher RPE and more lactate associated with the workload - longer work period and shorter rest period than 30/30. Here’s a chart from some guy named Astrand 
from before I was born. This chart shows the same amount of work being done at similar work/rest ratios but different durations and the lactate response.
It’s not the US. Cog has his own set of them that he drops often.
Go ahead and FMPFM Cog! 
Matej Mohorič has some insightful things to say about all of this.
The whole podcast is a worthwhile listen and here:
Who is Anthony Walsh and how does he get all these top people to go on his podcast? I had never heard of him until the Lemond interview came out.
They may be acronyms based on the English language, but I didn’t invent any of them (well, except for PPP). I have just been participating online since the Usenet days.
I’ve been on forums for decades going back to usenet and this is the first time I’ve heard of FYPFY.
The other one I’ve seen used a bit more often is FIFY (Fixed It For You).
Or IFYPFY.
