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


@Jonathan & @Ian this would be a great topic for the AACC podcast. Might need to assign a fair amount of time to it though!!
Links to so many threads on here.


I summerized all the details on my INSCYD test in the post below. I hope you guys can help me what to make of it.


It is always entertaining and informative when they try out a performance testing protocol and report back on the podcast. INSCYD is less invasive than a muscle biopsy.


@roflsocks I’m doing a deep dive on vlamax, but haven’t watched the webinar yet. Have some preliminary observations and questions.

First observation - if I replace “vlamax” with classic sugar-vs-fat burning narrative, then everything I’ve read about VLaMax appears to map conveniently back to all other stuff I’ve learned over the years. In other words:

  • high VLaMax means you are sugar burner (carb burner)
  • low VLaMax means you have improved fat burning % at higher intensities

Given that, I’m a little confused as to why LSD/base is listed as either raising or lowering vlamax. It has been known for many years that if you properly commit the time to LSD/base, it will improve fat burning (plus aerobic system improvements).

Do you recall if the webinar explained reasoning for arrows in each row? Thanks!


It does! Watch it! :sweat_smile:


yes, I’ll register, hopefully this weekend, and watch it. I’ve got some more observations, what I wrote above is somewhat an oversimplification.

Thanks for sharing your report in the other thread!


I watched it on youtube, but it’s not there anymore :open_mouth:


From what I understood, LSD doesn’t change VLAmax much due to its low recruitment of type II fibers.


In order to train VLamax to lower, you need to be engaging your fast twitch fibers. This is why sweet spot works well for lowering it, because power is high enough to engage these fibers, and intensity is low enough to not increase anaerobic capacity.

If you’re doing long slow base, intensity may be so low that these fibers aren’t being utilized much. And if you stop training a muscle fiber, they’ll start to detrain. I don’t believe the detraining effects on VLamax were discussed at all, but my intuition is that since an untrained rider has a relatively high VLamax, failure to maintain training to keep it low would result in an increase, as the muscle tends to return to its default state.

This can be countered by doing low cadence work. At low cadence, you’re requiring enough torque each pedal stroke that you’ll resume engagement of your fast twitch fibers. You can low cadence pretty much anything, so the exact response will differ depending on which zone you’re training in, but for everything around 120%-ish and lower, these are still highly aerobic efforts. And doing low cadence aerobic work is great for lowering VLamax.

Similarly, high intense workouts depend on what you’re doing. If you’re doing repeats with short rest at high power, these are mostly aerobic. If you’re instead doing repeats with a long rest, these are much more of an anaerobic stimulus. The later will increase VLamax. Similarly, sprints and weight lifting is mostly an anaerobic activity, and will similarly increase VLamax.

Improving fat burning is an aerobic process. Lowering VLamax is on the other hand, a change in your anaerobic process. It seems like there’s probably a reasonably strong correlation between the two, but they’re not quite directly related.

Burning carbs is always an anaerobic process. Essentially the glycogen(carbs) gets converted into lactate via the anaerobic system, and then the aerobic system takes that lactate, and uses it to generate power. If you’re at a sufficiently low power output, you won’t be generating enough lactate to meet your power requirements, and you’ll supplement with having your aerobic system also burn fatty acids.

And apologies for the wall of text. It gets lengthy quickly when trying to be specific about these things.


Not the only way. VLaMax is rate of lactate production.

    1. In order to reduce lactate production, you can increase preference for fat as a fuel by using LSD/base training methodologies, and via low carb training.

and to your point:

  1. Reducing lactate production also happens when you convert type IIx fast twitch muscle fibers to IIa, because the IIa will use more fat for fuel and therefore reduce lactate production. Both tempo and sweet spot are good zones to promote conversion of IIx to IIa.

or rewriting in the language of VLaMax:

  1. In order to reduce VLaMax, you can increase preference for fat as a fuel by using LSD/base training methodologies, and via low carb training.

and to your point:

  1. Reducing VLaMax also happens when you convert type IIx fast twitch muscle fibers to IIa, because the IIa will use more fat for fuel and therefore reduce VLaMax. Both tempo and sweet spot are good zones to promote conversion of IIx to IIa.


That’s why it is called long slow (steady) distance. You have to go long enough to exhaust your ST fibres. From the classical review paper on motor unit recruitment patterns:

Saltin (1981):

In very light dynamic contractions repeated for hours there is a primary reliance on slow twitch (ST) fibres with no or very minor involvement of fast twitch (FT) fibres. At heavier work loads (greater than 50% Vo2max) ST fibres are depleted first but FT fibres begin to become depleted. Exhaustion at these work levels coincides with muscle fibres of all types being depleted of glycogen.

less than 50% VO2max is more or less active recovery intensity. Or perhaps the lower end of LSD. However, more likely is an intensity of 50-65% VO2max. And here with sufficient duration you get to your FT fibres eventually. And what is particularily important, through a different (biochemical) mechanism then by high intensity.


I’d like to conmend the posters on this thread, doing a super job of explaining things. Nice work.


Great answer.

Higher VO2max, lower VLaMax, and higher FatMax. That’s all I need to know how to do. very simple really :grin:

The chart above would be even better with a FatMax column added.


This was my initial confusion also on how to reduce VLaMax. I assumed LSD was the way to go to improve fat metabolism.

But conversion of IIx into IIa also makes sense, hence the need for SS workouts.

I’d add to this and say that IIa burn carbs more areobically than IIx. I.e. less lactate formed when IIa burn carbs than IIx. At SS intensities, the majority of energy is likely coming from carbs. So SS workouts train this mechanism. LSD workouts probably more train the fat burning mechanism.


three basic ways:

  1. LSD to increase preference for fat as fuel
  2. Carb restricted training, to increase preference for fat as fuel
  3. SS/Tempo to convert IIx muscle fibers to IIa

all of those will shift “fuel blend” to more fat burning, and therefore reduce lactate production (VLaMax). Might have forgotten something, those are the three that come to mind.

p.s. all the confusion disappeared when I stopped using “decrease VLaMax” and started thinking “increase preference for fat as fuel” because everything already written on the topic uses that jargon-free language


I’m not sure that I agree that increasing fat for fuel has an affect on VLamax. Fat metabolism seems to be an entirely aerobic function. Fatmax occurs sub-threshold, above which fat contribution decreases.

When performing a lab test to calculate VLamax, a 15 second max effort sprint is used to generate a max lactate value. You’re going to have basically zero contribution from fat at that high of an intensity.

The webinar had a few minutes where they went over the metabolic process in pretty good detail. They highlighted fat usage as a complementary aerobic energy source, for when you’re working sub threshold and you need additional power after all available lactate has been consumed.


Not going to directly debate that point, I’m keeping things simple. My basic understanding is that when you train in ways that result in increasing preference of fat as fuel, you end up increasing the % contribution of aerobic energy at nearly all levels of intensity (ignoring edge cases like sprinting).

The aerobic energy system has 4 inputs:

  • oxygen
  • pyruvate/lactate (output of anaerobic energy production)
  • fats
  • proteins

So the output of carb burning (anaerobic energy) is one of the inputs to aerobic energy production.

Now look at the chart on page 4 of the INSCYD white paper INSCYD+white+paper±+VLamax±V1.pdf

Lower VLamax = less energy from carbs (anaerobic system) and more from fat (aerobic system). Energy comes from a “fuel mix” in pretty much all situations except for short sprints.

One mechanism for lowering VLamax is increasing % of fat for fuel, or said another way, increasing aerobic system % contribution when exercising at nearly all levels of intensity as seen in the chart above.