I’ve pretty much kept volume the same during those blocks.
I totally don’t disagree that it all stacks but I wouldn’t say the blocks were just ‘sharpening up’ or a ‘verification block’. I did 9 VO2 workouts in 16 days, all high cadence, gasping for air, max effort. I’d be shocked if something that difficult didn’t cause some meaningful physiological changes.
But that’s what I’ve been saying. We didn’t hold anything constant. My FTP just was effectively constant. FTP isn’t just some power that you can hold for 45-70 minutes. It’s a functional inflection point that happens to fall in that time range. Sure, I probably could have gone and done a 40min TiZ workout at 315. But all those intervals would have been over threshold.
But in the end, I’ve done less intense times with some VO2s thrown in and while I might have sharpened the top end for racing, my FTP wouldn’t move and I had ~2 years of stagnant FTP despite training and riding consistently. So whether these super concentrated and intense VO2 blocks are ‘uncovering’ fitness or actually creating new levels of fitness it doesn’t really matter to me. I just know that at the moment that’s what it took (and still takes) for me to improve my FTP. And because it’s such a step change that happens within a month of those blocks I’m pretty confident it’s because of them.
And I’d say, this isn’t just something I’ve come up with on my own. It’s a pretty well regarded way to train to increase your FTP. That once you’re well trained, riding at FTP doesn’t do much to increase your FTP but VO2 workouts do. Just from a couple days ago here’s a post by a coach elsewhere on this forum describing the same kind of periodization (3rd and 4th paragraphs): Sweet Spot Progression - #3430 by kurt.braeckel