VO₂max vs. Lactate Threshold: Which Metric Matters More for HYROX Performance?

By Karyn Guidry, Karyn Guidry Fitness

When most athletes think about endurance performance, they immediately think about VO₂max.

It’s often treated as the gold standard of fitness.

The higher your VO₂max, the fitter you must be.

But if you’re training for HYROX, marathon running, or hybrid racing, VO₂max only tells part of the story.

After coaching athletes and competing myself, I’ve found that some of the biggest performance differences come from what an athlete can actually do with their aerobic capacity.

Two athletes can have similar VO₂max scores and completely different race results.

Why?

Because HYROX performance depends on much more than your ability to consume oxygen.

It depends on your ability to sustain a high percentage of your aerobic capacity, run efficiently, manage fatigue, and continue producing output after every station.

To understand what actually matters for HYROX performance, we need to look at three key factors:

1. VO₂max
2. Lactate threshold
3. Running economy

Let’s break down what each means and which one may matter most on race day.

VO₂max is the maximum rate at which your body can take in, transport, and use oxygen during intense exercise.

Think of it as the size of your aerobic engine.

VO₂max is influenced by factors including:

• Cardiac output
• Stroke volume
• Blood volume
• Capillary density
• Mitochondrial function
• The muscles’ ability to extract and use oxygen

A higher VO₂max generally gives an athlete greater aerobic potential.

Elite endurance athletes often have exceptionally high VO₂max values.

But here's the important part:

Having a bigger engine doesn't automatically mean you know how to use it efficiently.

That distinction becomes extremely important in HYROX.

VO₂max is useful.

But it's often overemphasized because it's relatively easy to measure and compare.

HYROX isn't a 5 minute maximal effort.

You have to run 8 kilometers while repeatedly completing demanding functional stations.

That means you need to maintain a high level of output without reaching your maximum capacity too early.

Two athletes could have the same VO₂max but very different HYROX performances.

Why?

VO₂max doesn't tell us everything about:

• How fast you can run at a sustainable effort
• How long you can maintain a high percentage of your aerobic capacity
• How efficiently you use oxygen while running
• How quickly you recover between efforts
• How well you manage fatigue
• How much energy you use to maintain your pace

That's where lactate threshold and running economy become so important.

Lactate threshold describes the intensity at which blood lactate begins to accumulate more rapidly because production is outpacing the body's ability to process and clear it.

As exercise intensity increases, lactate production increases too.

At lower intensities, your body can continuously produce, use, and clear lactate.

As intensity continues to rise, you eventually reach an intensity where maintaining that effort becomes much more difficult.

You'll notice:

• Breathing becomes harder
• Heart rate rises
• Muscular fatigue increases
• Maintaining your pace becomes more difficult
• Sustained efforts become increasingly challenging

For trained athletes, threshold intensity often occurs at a relatively high percentage of VO₂max, although the exact percentage varies significantly between individuals.

And this is where HYROX gets interesting.

HYROX requires you to repeatedly operate at challenging intensities while transitioning between running and functional stations.

You don't just need a big aerobic engine.

You need an engine you can use for a long time without blowing it up.

Think about two athletes.

Athlete A	Athlete B
VO₂max: 65 ml/kg/min Lactate threshold: 75% of VO₂max	VO₂max: 60 ml/kg/min Lactate threshold: 90% of VO₂max

Athlete A has the larger aerobic engine.

But Athlete B can sustain a much higher percentage of their capacity before reaching their threshold.

That can become a major advantage in a long, demanding event like HYROX.

This is why I care about more than just an athlete's VO₂max.

I want to know:

How fast can you go without falling apart?

Because that's what matters when you're trying to maintain your pace through all 8 kilometers and still have enough left to handle the stations.

A higher lactate threshold can help you:

• Sustain faster running speeds
• Maintain a higher output for longer
• Delay excessive fatigue
• Recover more effectively between hard efforts
• Maintain better pacing late in the race

This is one reason threshold training is so valuable for HYROX athletes.

There's another metric that deserves far more attention.

Running economy.

Running economy refers to how much oxygen and energy your body requires to maintain a given running pace.

Think of it as fuel efficiency.

Imagine two athletes running at the exact same pace.

Both have:

• Similar VO₂max
• Similar lactate threshold

But Athlete A uses less oxygen to maintain that pace.

Athlete A has better running economy.

That means they can potentially maintain the same speed with less energy expenditure.

Over 8 kilometers, that matters.

Now add:

• Sled pushes
• Sled pulls
• Burpee broad jumps
• Rowing
• Farmers carries
• Sandbag lunges
• Wall balls

The athlete who can run efficiently while fatigued has a major advantage.

HYROX isn't simply about how fast you can run fresh.

It's about how efficiently you can run after working hard.

Every kilometer starts with some level of accumulated fatigue.

Your legs aren't fresh after the sled push.

Your breathing isn't fresh after the SkiErg.

Your body isn't fresh when you start the final two kilometers.

Running economy becomes even more valuable as fatigue accumulates.

If your running mechanics become inefficient when you're tired, your energy cost increases.

That can make every subsequent station feel harder.

Improving running economy means becoming better at maintaining efficient movement even when you're fatigued.

That is a major HYROX skill.

If I had to look at the aerobic side of HYROX performance, I'd pay attention to three major qualities:

1. VO₂max Your aerobic ceiling. It tells us how much aerobic capacity you potentially have.

2. Lactate Threshold Your ability to sustain a high percentage of that capacity. It tells us how fast you can go before fatigue begins accelerating.

3. Running Economy How efficiently you use that capacity while running. It tells us how much energy it costs you to maintain your pace.

None of these metrics should be viewed in isolation.

A great HYROX athlete needs the combination.

A big engine.

A high sustainable output.

Efficient movement.

If you're asking me to choose one metric to focus on, I wouldn't tell you to obsess over your VO₂max.

I'd focus more on your ability to sustain a fast pace and maintain efficiency under fatigue.

That's why lactate threshold and running economy are so important for HYROX.

A higher VO₂max gives you potential.

But if you can't sustain a high percentage of it, that potential doesn't translate into race performance.

And if you're wasting energy every kilometer because your running economy is poor, you're making the race harder than it needs to be.

For most HYROX athletes, the goal isn't simply to build the biggest aerobic engine possible.

It's to become better at using the engine you already have.

You don't necessarily need expensive laboratory testing to become a better HYROX athlete.

VO₂max Testing

VO₂max can be assessed through:

• Laboratory metabolic testing
• Treadmill testing
• Cycling testing
• Performance based field estimates
• Wearable based estimates

Laboratory testing provides the most direct measurement, but field testing and performance data can still be useful for monitoring progress.

Lactate Threshold Testing

Lactate threshold can be assessed through:

• Blood lactate testing
• Laboratory threshold testing
• Field based threshold tests
• Structured time trials

For athletes without access to laboratory testing, consistent training data can also help identify changes in sustainable pace and performance.

The important thing is not becoming obsessed with one number.

Use testing to guide training, not define your fitness.

The good news is that you don't need completely separate training systems for each metric.

A well designed endurance program can improve both.

1. Build Your Aerobic Base

Zone 2 and other low intensity aerobic training help build the foundation that supports higher intensity performance.

Benefits include:

• Improved aerobic capacity
• Increased mitochondrial adaptations
• Improved ability to use fat as a fuel source
• Better recovery between hard efforts
• Increased endurance

For HYROX athletes, this foundation allows you to handle more training while improving your ability to sustain effort.

Depending on your training history and goals, this might include 2 to 4 aerobic sessions per week.

2. Train Your Lactate Threshold

Threshold training teaches your body to sustain a faster pace for longer.

Examples include:

• 3 x 10 minutes at threshold effort
• 4 x 8 minutes at threshold effort
• 20 to 40 minute tempo efforts
• Longer controlled intervals with short recovery periods

The exact pace should be individualized.

Threshold training should feel hard and controlled, not like an all out sprint.

The goal is to improve the pace you can sustain, not simply to make yourself exhausted.

3. Include VO₂max Intervals

Higher intensity intervals can help improve your aerobic ceiling.

Examples include:

• 5 x 3 minutes hard
• 6 x 800 meter repeats
• 4 x 4 minute intervals

These sessions are demanding, so they should be used strategically.

More intensity isn't automatically better.

Your goal is to create an adaptation, not accumulate unnecessary fatigue.

4. Improve Running Economy

Running economy improves through consistent running and better movement efficiency.

Focus on:

• Consistent running volume
• Strength training
• Running mechanics
• Appropriate running intensity
• Strides and controlled speed work
• Maintaining good form as fatigue increases

For HYROX athletes, I also want to see athletes practice running after stations.

Because running efficiently while fresh is one thing.

Running efficiently after a sled push is another.

5. Strength Train

Strength training can support both running economy and HYROX station performance.

Prioritize movements such as:

• Squats
• Deadlifts
• Split squats
• Lunges
• Carries
• Pulling movements
• Core stability

For most HYROX athletes, 2 to 3 well structured strength sessions per week can complement their running and aerobic work.

The goal isn't to become a powerlifter.

The goal is to become strong enough to handle the stations while maintaining your endurance performance.

If you're preparing for HYROX, I wouldn't build your entire training program around improving one metric.

Instead, I'd build the complete athlete.

Focus on:

Aerobic base

Build the engine.

Lactate threshold

Increase the pace you can sustain.

VO₂max

Raise your aerobic ceiling.

Running economy

Become more efficient.

Strength

Build the ability to handle the stations.

Race specific conditioning

Learn to maintain output while fatigued.

Pacing

Learn how hard you can actually race.

That's what turns fitness into HYROX performance.

The biggest mistake I see athletes make is chasing numbers instead of building performance.

They want a higher VO₂max.

A faster 5K.

A heavier squat.

A better SkiErg split.

Those numbers can be useful.

But none of them matter if you can't put them together on race day.

HYROX performance comes from combining these qualities.

You need to run well.

You need to handle the stations.

You need to recover between efforts.

You need to manage fatigue.

And you need to maintain output when your body starts telling you to slow down.

That's the real test.

If you're training for HYROX, don't obsess over VO₂max alone.

VO₂max gives you the potential.

Lactate threshold helps determine how much of that potential you can sustain.

Running economy determines how efficiently you use it.

The athletes who perform best aren't always the ones with the biggest aerobic engines.

They're the athletes who can sustain a high percentage of their capacity while moving efficiently under fatigue.

Build your aerobic base.

Improve your threshold.

Raise your aerobic ceiling.

Become a more economical runner.

Build enough strength to handle the stations.

Then learn how to put it all together.

Because HYROX isn't about having the biggest engine.

It's about knowing how to use it when the race gets hard.