Good catch! I love this so much. You’re right in that the discussion should be vo2max vs anaerobic power, as we mentioned about the original Tabata study. But you bring up something that got left on the cutting room floor.
Here’s the long version about work rates and 20min test and whatnot that I cut out of the podcast, since it weaved in and out of a tangential discussion about getting into averages vs individualizing datapoints, RPE, instructions and compliance, and how we can see conflicting data points resolve when we look at individual points. We might include it as an addendum in the next episode since it probably does need to be addressed.
79+/-7% wmax interval avg work rate average likely shows a heavy left skew and sure, some working over FTP but most not. Here’s how I figured that. Looking at individual responses, we can probably say three were working over FTP who did show a positive response, the rest were not, or I’m absolutely certain they would have shown a bump in vo2max. But this is a problem covered up by the averaging so we’re left with educated guesses.
We can try to use power at 4mmol to approximate FTPs, so we have a conflicting data point in the study where it’s about 320-330w and yet 368w is only 79% of Wmax, what we might estimate as vo2max power. So by this data and knowing most elites are at FTP around 80% vo2max but almost definitely more like 85% or more. 330w around 70% of Wmax (or estimating threshold around 70% vo2max) is REALLY low for an elite endurance athlete. So 4x5 is either working above threshold by a couple watts, or below threshold by a couple % vo2max. Conflicting data point brought about by the methodology. If all of them were working over threshold, I’m sure we’d have seen the same (as 30/15s) or better response in vo2max in the 4x5 group. But this gets resolved.
I’m sure 4mmol power (general population average for MLSS concentration) underestimates FTP in a ramp test by a lot, which sounds a little like heresy at first, but we just can’t use this to estimate threshold and here’s why.
As you begin to recruit new motor units as power output goes up, they start with a bump in lactate as glycolytic flux “covers the over” for a few minutes and then settles down. I’ve seen countless ramp tests that show 4mmol, or just plain inflection point as determined by Dmax or whatever other method you want to use, at 30-50w below FTP. Someone who does this right is San Millan, who looks at blood lactate in the right way, having people do a 10 minute steady power output and measures blood lactate only at the end. Just opening up a random ramp test with lactate data, looks like this guy’s FTP by blood lactate ramp test is about 300-310w, but in reality is 360-370w. So without letting the fresh motor units get used to their new duties, blood lactate is way higher than it’d be without a period of settling in.
20min test: this followed the ramp test after 20 minutes rest. Any coach who’s ever had folks do the 5min blowout before 20min test knows that this doesn’t increase 20min test accuracy at all, it reduces it to the point of uselessness. Some folks can barely do FTP or SST watts at that point, so I had dismissed it in this study as a valid test to estimate FTP, or even maximal 20min power. The point about increasing anaerobic and buffering capacity, better trained larger motor units still holds up here. Anyway, that’s why for the 20min test the groups averaged 5-7mmol to start.
The protocol says they aimed for highest average power output “for each session”, but this is part of the RPE problem, and problem with instructions. The Borg scale is so weird anyway, it’s out of 20 and there’s very little granularity with how we describe RPE on the bike, which is why I’ve never used it to describe anything to athletes. It’s more like for people who don’t really exercise… Borg’s 19-20 is something “you can’t maintain for long”. How long is long? Does it have to be a sprint? So okay, now we have 14 is basically endurance pace (not out of breath), and 19-20 is a sprint or damn near. Not much room to work with. VO2max intervals usually rate an 8-10 for my athletes, FTP 7-9 depending on duration… but those all feel very, very different from each other regardless, so there wasn’t great control of actual work intensities, and whether or not power values wandered at all doing 4x5s and figured some fatigue came into play, but either way they were definitely not working that hard regardless of the instructions.
This is why I went with the estimation method I did, and made a rough assumption, plus the individual responses, that most of the 4x5min intervals were generally at or below FTP, and the distribution of actual 5min interval power outputs skewed low.