What is VLamax in plain terms?

VLamax measures how fast your muscles can maximally produce lactate. The higher that value, the more explosive you are over short, hard efforts. But that same trait also means you build up lactate faster during endurance efforts, which can hold back your endurance performance.

Is a high VLamax good or bad?

Neither, on its own — it depends on your goal. For a sprint or a short, explosive effort, a high VLamax is an advantage. For endurance sports like running, cycling, swimming or triathlon, a lower VLamax usually works in your favour, because it raises your threshold and lets you make better use of fat as fuel.

Can I change my VLamax through training?

Yes. VLamax is one of the most trainable traits we measure. With the right, consistent training stimulus, the first shifts are usually visible after six to eight weeks, and it can take several months to reach the full effect. It also works the other way: without the right stimulus, or with too many short, hard efforts, your VLamax can actually rise.

How does HYTX measure my VLamax during the lactate test?

We derive VLamax from the lactate values we collect during your test, combined with your oxygen uptake or power output at each step. That lets us calculate your maximum lactate production rate without needing a separate, all-out sprint test.

Is a lower VLamax always better?

Not necessarily. A VLamax that's too low can limit your ability to sprint, attack, or produce a finishing kick. For most endurance athletes, the sweet spot sits somewhere in the middle: low enough for a high threshold and efficient fat burning, high enough to still have another gear when you need it.

11 September 20265 min readCoachingWetenschap

VLamax: what it is and why we measure it

VLamax shapes how your muscles burn carbs versus fat. It's the number your lactate test reports — here's what it means and what the science says.

Spotted a value called VLamax on your lactate test results and wondered what it actually means? VLamax describes how fast your muscles can maximally produce lactate, and that trait shapes nearly everything about your endurance performance: from how many carbs you burn to how high your threshold sits. In this article we explain what VLamax is, why we measure it, and what recent science has uncovered about it.

Two engines: your aerobic and glycolytic systems

Your body essentially runs on two "engines" to produce energy during exercise.

The first is your aerobic engine, powered by oxygen. We measure that with VO2max: the maximum amount of oxygen you can take up and convert into energy. This engine is efficient and can keep going for a long time.

The second is your glycolytic engine. It produces energy from carbohydrates without needing oxygen, which means it can deliver power much faster — but lactate is a byproduct. The higher your VLamax, the more powerfully that second engine runs, and the more lactate your muscles produce per second.

Both engines are always running together, just in a different ratio depending on intensity. During an easy endurance effort, your aerobic engine does most of the work. During a sprint, your glycolytic engine kicks in hard.

Why a high VLamax can hold back your endurance performance

A powerful glycolytic engine sounds like it can only be a good thing. For short, explosive efforts, it is. But for endurance performance, a high VLamax has a downside.

The higher your VLamax, the more lactate your muscles produce at any given effort — even at fairly easy intensities. That has two consequences. First, the point at which your body can just about clear that lactate as fast as it's produced (your anaerobic threshold, also covered in our guide on training zones and the lactate test) ends up lower. Second, you burn proportionally more carbohydrate and less fat as fuel, since lactate is made from carbohydrate. That means burning through your glycogen stores faster, and slower recovery from lactate build-up in race situations where you need to surge repeatedly.

Two athletes with the exact same VO2max, body weight and efficiency can therefore still have a completely different threshold power — purely because of a difference in VLamax.

VLamax is trainable — which is exactly why we measure it

What makes VLamax interesting is that it isn't fixed. It's one of the most trainable traits we see on a lactate test, and it can shift quite a bit over a season: higher during an easy winter block, lower as you build specific endurance work toward your race, and higher again after a block of focused sprint or strength work.

That's exactly why we look at it at HYTX, alongside your VO2max and your thresholds. If we only looked at threshold power, we'd miss part of the story: a rising threshold power can be the result of a falling VLamax, which is great news for your endurance performance but less so for your sprint ability. By looking at both values together, we get a fuller picture of how your fitness is developing — and can shape your training accordingly.

Training it down: what most endurance athletes benefit from

For most runners, cyclists, swimmers and triathletes who train with us, a lower VLamax is the goal. Research and practical experience point to a handful of recurring principles:

Consistency. There's no shortcut. Lowering VLamax calls for regular, consistent training stimulus — usually three to six contributing sessions a week — rather than one long, hard session a week.
The right, moderate intensity. Too easy doesn't recruit the right muscle fibres, too hard triggers the opposite effect. The sweet spot sits just below your threshold, with enough force or resistance involved — for cycling, that can mean a slightly lower cadence than usual.
Avoiding short, hard peaks. Repeated short sprints or explosive surges activate exactly the glycolytic system you're trying to train down.
Refuelling on time, but not always completely. Training with slightly (never fully) lowered glycogen stores can help reduce your dependence on carbohydrate as fuel.

The first measurable shift usually shows up after six to eight weeks of consistent training. The full effect can take several months — which is why we retest your lactate values regularly.

Training it up: when that's actually the goal

For sprint power, a explosive finishing kick, or attacks during a race, the opposite is worth targeting. Think short, intense strength training (sets of roughly 12 to 30 seconds, with no rest between reps within a set), short sprint intervals with enough recovery in between, and staying well fuelled with carbohydrate to keep supporting that intensity. Here too: first effects after roughly six to eight weeks of focused training.

At HYTX, we work out together with you — based on your discipline, your target race and your test results — whether this is relevant for you. For most endurance athletes, a lower VLamax takes priority, but for anyone racing a sprint triathlon or needing a sharp finishing kick, a focused, temporary emphasis on the glycolytic system can pay off.

What this means for your training

VLamax isn't a stray number to skip past on your test results. Together with your VO2max and your thresholds, it gives us a fuller picture of how your body produces energy, and where the biggest gains are for you. We factor it into strength training, into nutrition coaching, and into how we build your programme with our running coaching, cycling coaching, duathlon coaching or triathlon coaching.

Curious about your own VLamax and what it means for your training? You'll find it on your own lactate test results, and your coach will walk you through it in plain language — not a stray number, but a concrete starting point for your next training block.

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