VO₂ Max Testing.
The maximum amount of oxygen your body can take in and use under effort. It is the most studied single marker of cardiorespiratory fitness, and the American Heart Association has proposed treating it as a clinical vital sign.
- Measured directly through gas analysis, not estimated from a wearable
- Establishes your ventilatory thresholds and true training zones
- The strongest predictor of mortality risk we can measure here
- Repeated later, so change is visible rather than assumed
One number, measured properly.
You wear a mask connected to a metabolic cart while cycling or running at progressively increasing intensity. The cart measures the oxygen you inhale and the carbon dioxide you exhale, breath by breath. The point where oxygen consumption plateaus despite increasing workload is your VO₂ max.
This is called indirect calorimetry, and it is the gold standard for assessing cardiorespiratory fitness. Everything else, from wearables to submaximal formulas, is an estimate of what this measures directly.
Breath by breath gas analysis · measured directly
Fitness is a mortality signal.
Of everything measured in longevity medicine, cardiorespiratory fitness has one of the strongest and most consistent relationships with how long people live. That is not a marketing line, it is what the epidemiology repeatedly shows.
It Predicts Mortality
Analysis of over 750,000 US veterans found each one MET increase in fitness, roughly 3.5 ml/kg/min, was associated with a 13 to 15 percent reduction in mortality risk. That held regardless of age, BMI, sex, or existing conditions.
- 13 to 15 percent per MET, across the whole range
- Independent of age, weight, and comorbidity
- No group was found too old to benefit
It Outweighs Body Weight
Pooled data from 398,716 individuals found that people with good cardiorespiratory fitness showed no significant increase in mortality risk regardless of BMI, while unfit individuals in every weight category carried substantially higher risk.
- Fit and heavier outperformed unfit and lighter
- Held for cardiovascular and all cause mortality
- Consistent across age groups
It Is Treated As A Vital Sign
In recognition of its predictive value, the American Heart Association advocates routine assessment of cardiorespiratory fitness and has proposed it as a clinical vital sign, alongside blood pressure and heart rate.
- Proposed as a clinical vital sign by the AHA
- More predictive than several conventional risk factors
- Rarely measured in routine care despite this
It Is Modifiable
Unlike age or genetics, this is a number you can move. Physical activity is the main modifiable determinant of VO₂ max, which is precisely why we measure it, build a protocol around it, and measure it again.
- Responds to training at any age
- Improvement is measurable within a protocol
- Gives your programme an objective target
More than one number.
The headline figure gets the attention, but the thresholds underneath it are what actually change how you train.
Your VO₂ max, measured rather than guessed
Your maximal oxygen uptake in ml/kg/min, compared against normative data for your age and sex. This is the ceiling on your aerobic capacity, and it is the figure the mortality research relates to.
Your ventilatory thresholds
The points at which your breathing pattern changes as intensity rises. These define where your training zones actually sit, and they frequently differ substantially from what a heart rate formula would predict for someone your age.
Your training zones, built from your data
Most people train using zones derived from an age based formula. Yours come from what your body actually did during the test. That is the difference between training in the right zone and training in one that was averaged from a population.
Who should be tested.
The short answer is almost everyone, though for different reasons.
Anyone training seriously who wants zones from data rather than a formula
People focused on longevity, where this is the single most informative measure
Anyone starting a protocol here, since it is the baseline everything is built from
People who suspect their fitness has declined and want to know by how much
Anyone relying on a wearable estimate who wants to know how accurate it is
Screening applies for cardiac conditions and certain medications
What to expect.
It is a maximal test, which means it ends when you cannot continue. That is the point rather than a warning.
Preparation
- Avoid hard training for 24 hours beforehand
- No caffeine within a few hours, and no heavy meal within three
- Hydrate normally and bring training clothing and shoes
- Tell our team about any cardiac condition or medication
The Test
- A mask is fitted and baseline readings taken at rest
- Intensity increases in stages, starting easy
- The last two to three minutes are genuinely hard
- You stop when you cannot maintain the workload. That is the endpoint
Your Results
- Cool down and recover, usually five to ten minutes
- Results the same day, with your zones explained
- Compared against normative data for your age and sex
- Retested at a defined point so change is measurable
Results the same day · zones built from your data
Stated as measurement, not outcome.
This is a test rather than a treatment. What it gives you is information, and what that information is worth depends on what you do with it.
Maximal oxygen uptake measured directly through breath by breath gas analysis
Comparison against normative data for your age and sex
Ventilatory thresholds identifying where your zones actually sit
Training zones derived from your data rather than an age based formula
A baseline that every subsequent protocol decision can be measured against
An objective retest, so improvement is demonstrated rather than assumed
Context for how accurate your wearable estimate has been
A marker with a well documented relationship to long term health outcomes
This is step one.
Every protocol here begins with measurement, and this is the measurement it begins with. Without it, everything that follows is a reasonable guess.
We establish the baseline
VO₂ max and InBody together give us where you actually are, alongside whatever your consultation surfaces about what you are trying to change.
We build from the data
Your zones and your capacity determine which modalities are prioritised and at what intensity. This is what stops a protocol being a package.
We retest
Typically at eight to twelve weeks. The second number is what tells you whether the protocol worked, which is the entire reason for taking the first one.
A century of evidence.
VO₂ max has been studied for a hundred years and the relationship with mortality is among the most replicated findings in exercise science. These are the papers.
Each one MET increase in cardiorespiratory fitness, roughly 3.5 ml/kg/min, was associated with a 13 to 15 percent reduction in mortality risk, regardless of age, BMI, sex, or comorbidities.
Cardiorespiratory fitness and longevity
Cardiorespiratory fitness, body mass index and mortality
Measured versus estimated fitness
Accuracy of Apple Watch VO₂ max measurements
Association, and what it does and does not mean
The relationship between cardiorespiratory fitness and mortality is one of the most consistently replicated findings in this literature, across very large cohorts. Worth holding as you read it: these are observational associations rather than proof that raising your number causes you to live longer. Fitness also reflects underlying health, and causality runs in both directions. What is well supported is that fitness is modifiable, that it responds to training at any age, and that it predicts outcomes better than several risk factors that receive far more clinical attention. That is enough reason to measure it properly.
Questions answered.
My watch already gives me a VO₂ max. Why test?
Because a wearable estimates it from heart rate and pace using an algorithm, while this measures the gas you actually exchange. Validation studies show estimates can differ meaningfully from measured values. If your watch has been close, that is useful to know. If it has not, that is more useful still.
Do I need to be fit to take the test?
No. The protocol starts easy and increases gradually, and it ends when you reach your limit rather than at a fixed workload. Someone unfit simply reaches that point sooner, and that result is exactly the information worth having.
How hard does it actually get?
The final two to three minutes are genuinely difficult. This is a maximal test and the number depends on you reaching your ceiling. Our team coaches you through it, and the whole thing is over in well under twenty minutes of actual effort.
Is it safe?
Maximal exercise testing is well established and routinely performed, and we screen beforehand. It is not appropriate for everyone, particularly with certain cardiac conditions, and screening exists to identify that. Tell our team about any heart condition or medication before booking.
What is a good number?
It depends on your age and sex, and we compare you against normative data rather than a single benchmark. The more useful framing is direction rather than position. Where you sit today matters less than whether it is rising or falling.
How quickly can it improve?
Meaningful change is typically measurable over eight to twelve weeks of consistent work, which is why we retest at that point. How much depends on your starting position, your training, and your genetics, and we will not predict a figure in advance.
Why does it matter more than my weight?
The 2025 meta-analysis of nearly 400,000 people found fit individuals showed no significant increase in mortality risk regardless of BMI, while unfit individuals in every weight category carried two to three times the risk. That does not make weight irrelevant. It does suggest fitness deserves more attention than it usually gets.
How often should I retest?
At the end of a protocol, typically eight to twelve weeks, and quarterly thereafter for members. Testing more often than that rarely reveals anything the previous test did not.
Is it included in membership?
Baseline and retest are included within protocols. For members, access depends on your tier. It can also be booked on its own if measurement is all you are after.
Measurement comes first.
This is where protocols begin. These are the things it usually sits alongside.
Advanced Longevity Testing
The wider diagnostic picture, from body composition through to physician led panels.
Hyperbaric Oxygen
One of the modalities most often prescribed once your oxygen capacity is established.
Oxygen & Capacity
See how this measurement anchors the system addressing delivery, extraction, and utilization.
Reserve Your Consultation.
Testing is where your protocol starts. In your consultation we will:
- Understand what you are actually trying to change
- Screen for cardiac conditions and medications
- Schedule your baseline testing
- Explain what your numbers mean once we have them
- Build a protocol across the systems that matter for you