That Triathlon Show | EP#169 - FTP, VO2max and VLaMax


That’s a better way of making the point I was looking to make. The ramp test is a function of VO2 max, hence estimates FTP off VO2max. Which is not perfect, as people have differing VLaMax profiles, meaning FTP is a different % of VO2 max depending on the rider.


Thanks for taking the time @Mikael_Eriksson, and I can see this in my own history: plenty of work to do at the basic level.


Yep - more consistent and more volume is probably the solution for most of us!

Life realities (work, family, etc.) can make this hard, so then we start to look for other Silver bullets to improve performance. I’m certainly guilty of this!


From the FAQ’s:

Do a 4-minute Time Trial. Your effort must be overpaced, ie. you must start the effort significantly harder than what you can actually sustain. This is extremely important. Your power will inevitably start to decrease as you tire, but your only job is to simply go as hard as you can and hang on for dear life until the 4 minutes are up.

Do a 20-minute Time Trial. This too must be overpaced, as described for the 4-minute Time Trial.


my life commitments make it hard for me to go out for long workouts. (Happy wife, happy life!) so I haven’t done much rides longer than 2 hours the past 4 years or so since becoming a father. However I still am getting a lot of the positive markers that we would normally associate with higher volume. Biggest factor IMO was not having that September/October dip in between previous season and starting base work.


Enjoyed this podcast. Especially at ~ the 43 minute mark where they start to talk about what specific training approches help to modulate VO2max/Vlamax.


I don’t follow. .84x 6-min. power should give you what? I just looked at my last ramp test and that equals a few watts less than .75x 1-min.


<5 few?


I wonder this too. Seems to make sense. Any comment @Mikael_Eriksson? Thanks for the very interesting podcast!


Yes, less than 5. Actually I made a slight math mistake before - they’re within 1W of each other. You’re suggesting then that .84x6-min. is just an alternative formula for deriving FTP from the Ramp? What’s the value?


I’m mostly merging a topic from another thread here. It appears that the relationship between FTP, VO2max and VLaMax will affect your fractional utilization of VO2 for FTP. The 75% of the 1 min max from the ramp test, appears to also mean that they are estimating the fractional utilization at roughly 84% of VO2 max (6 min power). Again, this would assume that the 6 min from the ramp is your best 6 min power, which may not be the case. For me, my highest ramp test produces my highest 5 and 6 min power in my personal record. It’s mostly just looking at the relationship between VO2max and FTP. If for you, steady state efforts are a bit too easy from the ramp, your fractional utilization is higher than 84% and if they are really hard, it might be lower.


From playing around with the example values in the podcast, I put together something that mostly does that. Given any two values, you can calculate the 3rd.

(1 + 1 / Vlamax / Vc) * Vo2max * Pc = FTP

This uses two constants, one is a multipler for vlamax, and one for overall power output.
Vc is the Vlamax constant: approx 7.43
Pc is the power constant: approx 3.45

You need Pc, because otherwise the resulting numerical value is in arbitrary units, and not watts. Turns out my formula simply needs 3.45 arbitrary units per watt. And Vc is needed, to scale the difference between to different Vlamax values to the expected difference in performance.

I literally took data from two example athletes, and used those to generate the constants. A much more valid value for the constants would look at a large dataset, and pull the value that best matches.

The example athletes I used had the following data:
Vo2max: 50, Vlamax: 0.3, FTP:250
Vo2max: 63, Vlamax: 0.9, FTP:250

I plugged in a few more examples into my formula, and got FTPs that were close to expected. And then plugged in a couple more, and then saw the reported values vary a good bit more than expected. It’s clearly not quite the right values as is. Should be close enough to get an idea for how things are working though.

I’ve spent way too much time lately digging down this rabbit hole. Feels like it’s starting to make sense now, although it’s completely changed how I was looking at the relationship between aerobic and anaerobic energy systems. There were quite a few bold claims about how much of performance can be explained by the relationship between just vlamax and vo2max. Still have a bunch of research left to do on that though.


Yes - I think it’s possible to derive the third, if you know two of VO2max, FTP, and VLaMax.

But to do so, FTP needs to be a “true” FTP i.e. that estimates power at MLSS.

If FTP is gotten by just taking a % of VO2max, then this doesn’t help. They need to be independent measurements.


I’ve seen @Mikael_Eriksson reference FTP is predicted with 98% accuracy by VO2mac and VLaMax.

This means someone out there has done a regression and has the resulting equation linking all these three.

My guess is that’s what’s the crew at INSCYD have done, but it’s a proprietary model.


This is a plot of your function FTP(VLamax, VO2max):


@roflsocks: Well done! It is a very good start to get an idea about sensitivity. We have to take into account that different power meters/trainer give different values and also upright versus aero position has a significant impact on FTP. There will always be some inaccuracy in the formula.

There are tables about what is a good VO2max value for your age or tables that show running times per VO2max so one can get an idea about improvement potential.

My VO2Max is about 50 and I have an idea how hard I have to work to get it a point up but I don’t have a feeling for VLaMax values.

Has anybody seen VLaMax tables/thresholds that help to get a feeling?


Looks good. I think showing some isoquants for FTP on a 2D chart would even be better for readability…


Yes, if you know two the third can be calculated. Not sure what the formula is, I know it can be done in the INSCYD software at least.

But @abalakov when you say FTP can be tested - a classic FTP-test has zero value in this case. And even a lactate test isn’t really that accurate. Same goes for estimating VO2max.

Garbage in garbage out applies. You would need to do a VO2max test and use VT2 as your anaerobic threshold and of course your measured VO2max. Then you have two of the three, and based on biochemistry I guess it would be possible to figure out what the formula is.


This is a great observation.

I don’t yet have a massive data base of tests to draw from, but from what I’ve seen so far, a fractional utilisation of 76-80% is not at all unusual (the lowest I’ve seen is in the 73s) and neither is 86-88%.

84% may well be pretty good as an average but the variance is big.


LaMax benchmarks:
Elite Ironman Athlete - 0.3
Classics Rider/Draft legal triathlete - 0.5
Track cyclist - 0.9

As for inaccuracy based on being in aerobars or not - that’s not an inaccuracy, but your VO2max is actually different if you’re in the aerobars vs. if you’re sitting up, just as your cycling and running VO2max is different, and your sea-level and altitude VO2max is different. So context is very important. I advise long-course triathletes and time trialists to test in the aerobars. The VO2max number will always be a disappointment, but the information for training is going to be specific for the way they should and will be doing most of their training. Similarly, values are typically lower indoors compared to outdoors, but for athletes training mostly indoors I advise doing the testing indoors to get the data that is the most contextual for the athlete rather than the most flattering or ego-boosting.


There is a regression model in there for sure, but it’s as far as I’m aware not fundamentally built upon just a regression model, but actually on an equation system of biochemistry, because we know exactly how much ATP can be produced anaerobically with glycolysis and aerobically with oxygen etc. Exactly how it works I don’t know, and the regression model is in there for sure to match the critical power tests probably to energy produced via different systems, and then the equations can be solved. But yes, this is INSCYD’s proprietary model. And 98% (97.5% to be exact) is also correct from what Sebastian has said.

Also, spot on about it needing to be an independent “true” FTP.