Lactate threshold vs VO2max: which one HYROX actually taxes

VO2max is your ceiling. Lactate threshold is how much of that ceiling you can hold. A HYROX race lasts an hour or more, far too long to sit at VO2max, so the pace you can keep is decided mostly by your threshold, with VO2max setting how high that threshold can go. The one lab study of HYROX found higher VO2max went with faster finishes, but it didn't measure threshold, so the second half of that answer is an inference, not a finding.

hybridAF is not affiliated with HYROX.

Two different numbers#

VO2max is the most oxygen your body can use per minute, flat out. It's limited mostly by oxygen delivery, and it sets the upper limit for endurance performance: you can't work above 100% of it for long.¹

If you lift, I put it this way: VO2max is your 1RM for cardio, a ceiling you can't hold. Lactate threshold is the last clean rep before the set turns into a grind, the line between "I can hold this" and "I'm about to blow up."

The science is messier than the analogy. A 2009 review counted 25 different lactate threshold concepts.² Most fit into a two-breakpoint model. The first is where blood lactate starts rising above resting levels. The second is the maximal lactate steady state: the highest intensity where lactate production and clearance still balance, so you can hold it. Above that, lactate keeps climbing until you slow down. When people say "threshold pace" they usually mean something near that second breakpoint, but different labs and different watches mean different things by it.

They also improve through different routes. Training raises VO2max mainly by increasing how much blood the heart can pump at max. The threshold side moves mostly through changes inside the muscle, like more mitochondrial enzymes, which let you burn more fat and pile up less lactate at the same oxygen use.¹ Different routes is part of why different sessions train them.

How they fit together#

The cleanest model comes from physiologists who study champions. Three things decide endurance performance: VO2max, lactate threshold, and efficiency (how much oxygen a given speed costs). VO2max and threshold together set your "performance VO2", the oxygen use you can sustain for the length of the event. Efficiency then turns that into speed.³

Put in numbers: if your VO2max is 50 and you can hold 80% of it for an hour, your sustainable oxygen use is 40. Raise VO2max to 55 at the same 80% and it becomes 44. Hold 85% of the original 50 instead and it's 42.5. Both routes move the same number. That's a worked illustration, not data, but it's the logic behind the model.

The older review says it more bluntly: speed at lactate threshold, which already folds in VO2max, economy and how much of VO2max you can use, is the best single physiological predictor of distance running performance.¹ That's why two runners with the same VO2max can race very differently. There's a fourth piece, oxygen uptake kinetics (how quickly you get up to speed aerobically), and training shifts the whole speed-and-duration curve to the right.⁴

What a HYROX race actually costs#

Brandt and colleagues ran the first lab study of HYROX in 2025: 11 recreational athletes, tested for VO2max first, then sent through a simulated Open race with heart rate tracked and blood lactate sampled after every run and station.⁵

The median finish was 86.5 minutes, with 51.2 minutes running and 32.8 at the stations. Average heart rate was 170.9 bpm, against a median max of 186 in their pre-test. They spent most of the race above 90% of max heart rate.

Share of a simulated HYROX by heart-rate zone

	Value (% of time)
Very hard (90 to 100%)	79.5
Hard (70 to 90%)	19.6

Median share of race time in each zone, 11 recreational athletes in a simulated Open race. Very hard is 90 to 100% of max heart rate, hard 70 to 90%. Source: Brandt et al., Front Physiol 2025.

Blood lactate averaged 6.3 mmol/L across the race, 6.2 after the runs and 6.6 after the stations, and peaked at 8.5. The highest heart rate, lactate and effort ratings all came at the last station, the wall balls.

So what did that tax? Nobody holds VO2max for 90 minutes. Lactate averaging around 6 mmol/L over a race that long looks like athletes sitting close to their personal ceiling for sustainable work and dipping above it at the stations. That's an interpretation built on the threshold model above, not a finding. Brandt didn't measure anyone's threshold, and there's no single lactate value that marks it for everyone.²

The stations were the harder part per minute. Average heart rate was higher at the stations than on the runs (173.7 against 168.9 bpm), so were lactate and perceived effort, and the heaviest stations were the shortest: a median 2.1 minutes for the sled push and 2.6 for the sled pull.⁵ The authors read those 2 to 3 minutes of heavy pushing and pulling as phases where anaerobic energy is a big contributor, inside a race that leans on both aerobic and anaerobic metabolism overall. Running took 51.2 of the 86.5 minutes, close to 60%, which is why the authors call HYROX a running-focused form of functional fitness racing.

That split matters for the question in the title. The stations spike you above whatever your sustainable ceiling is. The runs are where you either recover back under it or don't. An athlete with a higher threshold has more room to absorb the spike and still run the next kilometre at a decent pace. That last sentence is the model talking, not a measurement, but it's the reason threshold is the number most HYROX athletes should care about first.

What Brandt did measure was which athlete traits went with faster finishes. The strongest was VO2max (Spearman correlation minus 0.71, so higher VO2max, faster time), then weekly endurance training hours (minus 0.68), then body fat percentage (0.67, so more fat, slower). When they split the race, those links showed up for the runs and not for the stations.⁵ Eleven people is a small sample, and correlation isn't cause. But it's a running race with stations in it, and the engine matters most where most of the time is spent.

What a held pace looks like#

My first HYROX, Bangkok 2026, took 1:13:38, 197th of the 3,254 men in my race. The eight runs added up to 33:14, which ranked 127th. The stations added up to 33:39, which ranked 406th.⁶

Ken's eight runs, HYROX Bangkok 2026

	Value (min)
Run 1	4.58
Run 2	4
Run 3	3.92
Run 4	3.92
Run 5	4.08
Run 6	3.93
Run 7	3.92
Run 8	4.9

Run splits in minutes (4:35, 4:00, 3:55, 3:55, 4:05, 3:56, 3:55, 4:54). Run 8 includes the approach to the wall balls. Source: HYRESULT, men's results, read and checked 2026-08-19.

Look at runs 2 to 7. Six splits between 3:55 and 4:05, each one coming straight off a station. That's what holding a pace for an hour looks like, as opposed to visiting one. There's no lactate data from that race, so there's no way to say where that pace sat against my threshold. What the results do show is that the runs, the part of the race that's mostly engine, were where I placed best.

If you want your own split broken down this way, the HYROX splits analyzer does it from your results.

Training for both#

Training at threshold and training for VO2max aren't the same session. In the 4x4 trial, the group labelled lactate threshold, running continuously at 85% of max heart rate, improved VO2max significantly less than the two interval groups doing the same total work.⁷ Endurance training does improve things below the ceiling: it raises the muscle's mitochondrial enzymes, which means less lactate builds up at a given oxygen use.¹ That's the threshold side moving.

So the logic for a HYROX athlete is two jobs. Hard intervals to raise the ceiling, covered in how to raise VO2max without losing strength. And enough steady volume, including some sustained work near race effort, to raise the share of that ceiling you can hold. Brandt's link between weekly endurance hours and finish time points the same way, though it can't show cause.⁵ How much running you need for HYROX puts numbers on the volume side.

One caution. A 2007 review of the running research concluded there isn't enough direct evidence from trained runners to write precise prescriptions for VO2max, threshold or economy; most studies were small and loosely controlled, and recommendations lean on physiology as much as on trials.⁸ Anyone selling you an exact threshold protocol for HYROX is going past the data.

Which one to test#

If you can only measure one thing, measure what predicts the race. For an hour-long running event that's closer to threshold than to VO2max. In practice, a race or a hard time trial of 30 to 60 minutes probably tells you more about your HYROX engine than a VO2max number from your wrist. VO2max is still worth knowing, as long as you read it as a ceiling with an error bar. The VO2max by age chart shows how to read yours. Runs that fall apart after the stations are a different problem, covered in compromised running. The rest of the engine reading is on the engine hub.