Why a VO₂ Max Number Alone Does Not Tell the Full Story

VO₂ max is one of the most well-known measures in endurance performance.

It is often seen as the ultimate fitness score. Many runners, cyclists, HYROX athletes and smartwatch users know their VO₂ max number, or at least have an estimate of it. But while VO₂ max is useful, it does not tell the full story.

At Perform180, we use VO₂ max testing as part of a wider performance profile. We are interested in the number, but we are even more interested in what sits behind it. This is because a high VO₂ max does not automatically mean someone will perform well and a lower VO₂ max does not automatically mean someone cannot be a strong endurance athlete.

What Is VO₂ Max?

VO₂ max is the maximum amount of oxygen your body can use during intense exercise, it reflects the combined ability of your lungs, heart, blood and muscles to take in oxygen, transport it, and use it to produce energy. It is an important marker of aerobic capacity but performance is not decided by VO₂ max alone.

Distance running, cycling, triathlon and HYROX performance depend on several interacting qualities, including:

• VO₂ max

• lactate threshold

• running economy

• movement efficiency

• strength

• power

• fatigue resistance

• body composition

• fuelling

• recovery

• injury history

• training history

This is why a VO₂ max score should never be interpreted in isolation.

Two Athletes Can Have the Same VO₂ Max and Perform Differently

Imagine two runners both have a VO₂ max of 60 ml/kg/min which would suggest that on paper, their aerobic ceiling looks similar. However, one runner may be able to sustain a much higher percentage of that VO₂ max before lactate begins accumulating rapidly. They may also use less oxygen at the same running speed, meaning they are more economical while the other runner may have the same VO₂ max but a lower threshold and poorer running economy.

The result?

Same VO₂ max.

Very different performance.

This is why we need to look beyond the headline number.

Threshold Matters

Lactate threshold gives us insight into how much of your VO₂ max you can actually use for sustained performance and for many endurance events, this is crucial. f your threshold occurs at a high percentage of your VO₂ max, you can sustain a harder intensity for longer. However, if your threshold is relatively low, you may have a good aerobic engine but struggle to use it efficiently during races or hard training sessions.

This is why threshold testing is so valuable.

It helps answer questions like:

• What pace can I sustain?

• Where should my tempo runs sit?

• What intensity is genuinely aerobic for me?

• How much of my VO₂ max can I use?

• Am I limited by capacity or sustainability?

VO₂ max tells us your ceiling.

Threshold tells us how close to that ceiling you can operate.

Running Economy Matters

Running economy is another key part of endurance performance, it relates to how much oxygen you use at a given running speed. A runner with good economy uses less oxygen at the same pace compared with a runner with poorer economy which means they can often run faster or longer for the same physiological cost.

Running economy can be influenced by many factors, including:

• biomechanics

• strength

• tendon stiffness

• neuromuscular coordination

• fatigue

• footwear

• training history

• body composition

• pacing

• running technique

By looking at oxygen uptake across different speeds, we can begin to understand how costly different paces are for the athlete.

Durability Matters

Performance is not just about what you can do when fresh, the difference between good an great is about what you can still do when tired. This is especially important for sports such as marathon runners, ultra-runners, triathletes and HYROX athletes.

An athlete may test well in a short controlled environment but struggle to maintain pace later in a race because their physiology, muscles or movement quality deteriorates under fatigue. This is where performance testing needs to be interpreted alongside training history, race demands, strength data and fatigue resistance.

At Perform180, we do not just ask, “What is your VO₂ max?”

We ask, “Can you use your fitness when it matters?”

Don’t forget Strength and Power

It widely known that endurance athletes often underestimate the role of strength and power in both their performance and injury prevention.

With HYROX athletes, strength and power are obvious factors due to the Sled push, sled pull, lunges, wall balls and compromised running all requiring more than just aerobic fitness. However, for runners, strength can influence tissue capacity, force production, stiffness, running economy and injury resilience.

This is why our full performance profiling can include ForceDecks and DynaMo testing alongside VO₂ and lactate testing.

We want to know whether the limiting factor is:

• aerobic capacity

• threshold

• economy

• strength

• power

• asymmetry

• fatigue resistance

• injury-related deficits

• fuelling or recovery

A VO₂ max score alone cannot answer that.

Wearables Can Be Useful — But They Are Estimates

Smartwatches can be helpful for tracking trends over time.

They can estimate VO₂ max, monitor heart rate, track training load and provide useful feedback.

But they do not directly measure oxygen uptake.

Most wearable VO₂ max estimates are based on algorithms using data such as heart rate, pace, GPS, age, sex and bodyweight. This can be useful, but it is not the same as measuring expired gases during an exercise test.

Wearables are best used as part of the bigger picture.

A lab-based test gives us a more direct view of your physiological response. A watch can then be useful for applying that information in day-to-day training.

Why We Use VO₂ Max as Part of a Bigger Test

At Perform180, we do not dismiss VO₂ max.

It is an important metric.

But we place it in context.

We may combine VO₂ max testing with:

• blood lactate testing

• treadmill speed calibration

• heart-rate response

• pace or power data

• running economy markers

• RMR testing

• ForceDecks testing

• DynaMo strength testing

• injury history

• training history

• event goals

This allows us to move from “here is your VO₂ max” to “here is what is most likely limiting your performance and what you should do next.”

That is the difference between testing and useful testing.

What a VO₂ Max Test Should Help You Understand

A good VO₂ max test should help answer questions such as:

• What is my aerobic capacity?

• How does my oxygen uptake respond to increasing intensity?

• What pace or power is costly for me?

• Does my heart rate match my physiological response?

• Is my VO₂ max actually limiting me?

• Would threshold training be more useful?

• Would strength and economy work help more?

• How should I structure my training zones?

This is much more valuable than simply chasing a higher number.

The Bottom Line

VO₂ max matters.

But it does not tell the full story.

Endurance performance is influenced by aerobic capacity, threshold, economy, durability, strength, power, recovery and training history.

At Perform180 in Knutsford, we use VO₂ max testing as part of a wider performance approach. We help runners, HYROX athletes and active people across Cheshire, Manchester, Northwich, Warrington and Chester understand not just how fit they are, but what is actually limiting them.

Because the goal is not just to know your number.

The goal is to know what to do with it.