VO2 Master metabolic analyser worn on a mask
KZ Performance

MetabolicTesting

Coach reviewing live gas exchange data on a tablet beside a client wearing the VO2 Master mask
Live results, reviewed with you as the test runs
VO2 Master Analyser Measured by gas exchange, not estimated
Two tests, one metabolic picture

Your breath, measured
in real time.

The analyser sits on the mask and reads every breath as you take it: oxygen consumed, ventilation, tidal volume, breathing frequency. Nothing is inferred from your heart rate or your weight. What you see on screen during the test is your own gas exchange, second by second.

The VO2 Master analyser held above its case alongside the mask and filters
The analyserCalibrated before every test

What We Offer

Select a service to read the evidence

RMR Test

Energy expenditure at rest

VO₂ Max Test

How big is your engine?

VO₂ max is the most oxygen your body can take in, move and use in a minute. Think of it as engine capacity: a bigger engine cruises comfortably where a smaller one is redlining. It is measured, not guessed, by analysing the air you breathe out while the work gets progressively harder.

  1. Heart rate monitor fitted, mask fitted and the analyser calibrated
  2. Ten-minute warm-up on the treadmill or stepper
  3. Intensity increases in stages, every few minutes
  4. The test continues to exhaustion, and you decide when that is
  5. Thresholds and training zones are built from your own gas exchange
Firefighter in full kit and breathing apparatus wearing the VO2 Master analyser during a field test
Graded exercise testLab or field

Why measured beats estimated

Everything else is a guess
dressed up as a number.

Your watch, your treadmill and the calculator on a nutrition app all infer metabolism from heart rate, speed, age and bodyweight. None of them measure the one thing that actually defines it: the oxygen you consume and the carbon dioxide you produce. Here is what the validation research reports.

MethodReported errorWhat that means
Apple Watch VO₂ max 13.3% Mean absolute percentage error against indirect calorimetry, underestimating by an average of 6.1 ml/kg/min, with individual agreement running from 6 below to 18 above the lab value.
Apple Watch Series 10 14% correct In 40 adults tested against a metabolic cart, the watch placed only 14% of people in their correct fitness percentile band, and a further 34% one band away. Mean error 13.2%.
Wearables generally 10 to 15% An umbrella review covering 249 non-duplicate validation studies found wearables overestimated VO₂ max by roughly 15% in resting-based tests and 10% in exercise-based tests. Useful for trends, not for individual numbers.
RMR equations 1 in 3 wrong Mifflin-St Jeor lands within 10% of measured RMR more often than the alternatives, but roughly a third of individuals still fall outside that band. In athletes it significantly misestimates RMR at group level.
VO2 Master analyser 0.6% Mean percent error for oxygen uptake against a metabolic simulator in a 2025 independent assessment, tested alongside a COSMED Quark, which averaged 3.5%. Against a lab cart during cycling, mean differences were under 9%.

Combined assessment

Two halves of the same equation.

Fat loss is energy in against energy out. The RMR test tells you what your body actually spends at rest, so your calorie target starts from a measured number rather than a formula. The VO₂ max test tells you which intensities burn fat fastest and which build the engine. The two have opposite preparation needs, since RMR must be measured fasted while a maximal effort needs fuel in the tank, so we run the RMR first thing on arrival, then break for something to eat before the VO₂ max test later the same morning.

RMR sets the baseline

Your measured resting burn becomes the anchor for daily calorie targets, with no equation and no averaging you against a population.

VO₂ max sets the intensity

Your thresholds define the zones: where fat oxidation peaks, where you build aerobic capacity, and where you are simply accumulating fatigue.

What you take home

A report you can
actually train from.

VO₂ max, maximal heart rate, ventilatory thresholds and five training zones with the heart rates, speeds and calorie rates that define them, plus where you sit against population norms for your age and sex. Delivered the same day, with a session to walk through what it means for your training.

Graded exercise test report showing VO2 max, ventilatory thresholds and training zones
Sample reportGraded exercise test

Book an RMR test, a VO₂ max test, or both in one session.