Cardiorespiratory fitness
CPET (cardiopulmonary exercise test).
The treadmill or bike test, with a mask, that measures the single strongest predictor of how long you will live and how well.
By [NEEDS YOUR INPUT: Local performance lab partner — e.g. "OrthoCarolina Sports Performance" or wherever you typically send patients] · 12 biomarkers
Why it matters
VO2 max is the most powerful single predictor of all-cause mortality in the medical literature. The test runs 8 to 15 minutes on a treadmill or bike with a mask that measures every breath. The output is your true aerobic ceiling, your anaerobic threshold (the intensity at which lactate begins accumulating), and the substrate mix your body uses across exercise zones. From a partnership perspective, it converts a vague training goal into a numeric one. I can write zones into your Plan that move the needle, not the watch.
The difference between a fitness watch estimate and a CPET is the difference between a guess and a measurement. Watches infer VO2 max from heart rate and pace using algorithms. A CPET measures the gases you exhale directly. The watch number can be off by 10 to 20 percent in either direction. The CPET number is the ground truth.
What I read for
VO2 max relative to your age and sex percentile. The anaerobic threshold expressed in heart rate, pace, or watts. The substrate crossover point where you stop burning fat and start burning carbohydrate. Symmetry of effort across the test. The delta from prior tests when you have one.
I read a CPET as five separate questions, each one writing a specific change into your training Plan:
- What is your true aerobic ceiling, and where does it sit against your age and sex?
- At what intensity does your body switch from fat to carbohydrate as fuel?
- Where is your lactate threshold, in heart rate, pace, and watts?
- How efficient is your gas exchange, and is anything limiting your ventilation?
- What is the trajectory across tests over time?
What it measures
A CPET reads three layers at once: how much oxygen your body can use at peak effort, where your thresholds sit, and what fuel mix you burn across exercise zones.
Aerobic capacity. Your VO2 max is the maximum volume of oxygen you can use per kilogram of body weight per minute. It rises with training and falls with detraining. It is the single number that best predicts your decade ahead. The mask measures it directly from the gases you exhale, which is why a CPET-measured VO2 max is the ground truth and a watch-estimated VO2 max is not.
Thresholds. Your anaerobic (or lactate) threshold is the intensity at which lactate begins accumulating faster than your body can clear it. It defines the upper boundary of sustainable effort. Below threshold you can hold effort for hours; above it, minutes. I read this in heart rate, pace, and watts so it can be written directly into training zones you can use the next day.
Substrate metabolism. The respiratory exchange ratio (RER) tells me what fuel you are burning at every intensity. At low intensities your body burns mostly fat. At high intensities it shifts to carbohydrate. The crossover point — where fat oxidation maxes out and carb oxidation takes over — is a marker of metabolic flexibility. Strong metabolic health stays in fat oxidation longer and switches later. Metabolic dysfunction crosses over earlier.
See all 12 biomarkers
Aerobic capacity
- VO2 max (ml/kg/min)
- VO2 max percentile for age and sex
- Peak heart rate
- Maximum minute ventilation
Thresholds
- Anaerobic (lactate) threshold
- Ventilatory threshold 1 and 2
- Heart rate at threshold
- Pace or wattage at threshold
Substrate metabolism
- Respiratory exchange ratio (RER)
- Substrate crossover point
- Fat oxidation rate
- Carbohydrate oxidation rate
Who this is for
CPET is the right test when fitness, performance, or longevity is part of the conversation, or when symptoms have an exertional component that watches and standard tests cannot explain.
Common reasons I order it
- Longevity-focused training, where you want zones written against real data
- Performance athletes targeting a specific outcome (race, season, body composition)
- Unexplained exertional fatigue or breathlessness
- A return-to-fitness milestone after illness or a cardiac event (with your cardiologist's clearance)
- Body recomposition projects where fat oxidation rate is a lever
- Establishing a baseline before a major training block
Most patients are surprised by what they learn. The number that comes back is rarely what their watch said, and the thresholds are almost never where they assumed.
How collection works
- 1
We decide it is the right test.
A short conversation to confirm CPET answers your question. If you have a cardiac history, I make sure your cardiologist clears the test first.
- 2
You schedule the visit.
[NEEDS YOUR INPUT: How patients book — do you place the order through Healthie and they call the lab? Direct walk-in? Note any required steps so the patient knows.] The test itself takes 8 to 15 minutes of progressive effort. Plan on 60 minutes total at the lab for setup, the test, and a brief cooldown.
- 3
You wear the mask.
A pneumotachograph mask attaches comfortably over nose and mouth. ECG leads track heart rhythm. You start at an easy pace and the workload increases every minute until you reach maximum effort.
- 4
We read the results together.
Results come back within [NEEDS YOUR INPUT: typical turnaround, e.g. "the same week"]. We sit down with them and translate the numbers into specific heart-rate, pace, and wattage zones for your training, written into your Precision Health Plan.
How to prepare
Preparation matters because the test asks for a true maximum effort. Anything that limits how hard you can push limits what the test can read.
Eat normally: no need to fast. A light meal 2 to 3 hours before is ideal. A maximal effort on an empty stomach is brutal and reads poorly.
Hydrate the day before: aim for clear urine the morning of the test.
Caffeine and stimulants: [NEEDS YOUR INPUT: Your preference — many CPET protocols hold caffeine 12 hours before, some clinics allow it. Pre-workout stimulants are typically held the day of since they inflate heart rate readings.]
Hard training: avoid intense exercise for 24 to 48 hours before. You want fresh legs and lungs.
Beta blockers and rate-limiting medications: [NEEDS YOUR INPUT: We may continue or hold depending on the indication. Note your standard — and always include "never stop a heart medication without clearing it with me or your cardiologist first."]
Clothing: wear what you would wear for a hard workout. Athletic shoes, athletic clothes, a sweat towel.
If you are sick, postpone. A viral infection skews every measurement.
Bring a list of any medications and supplements you take.
What you get
A written report from the performance lab with all measurements and graphs. A debrief with me where we translate those numbers into specific training zones written into your Precision Health Plan. Zones for easy endurance, threshold work, and VO2 max intervals, with heart rate, pace, and wattage targets where applicable.
A repeat test in 6 to 12 months tracks progress. The trajectory is more useful than the snapshot. Most patients see meaningful gains within 12 weeks of structured training, often much sooner if they are starting from a sedentary baseline.
Questions
Your watch infers VO2 max from heart rate and pace using algorithms. A CPET measures it directly from the gases you exhale. The watch estimate is typically off by 10 to 20 percent and the direction of error varies by individual. The CPET is the ground truth.
If you train without thresholds you have measured, you are guessing. Most people work too hard in their easy zones and not hard enough in their threshold zones. A single CPET clarifies both ends of that distribution and usually reshapes a training week within the first session.
The test is a controlled maximal effort under ECG monitoring with a clinician present. Adverse events are rare in screened individuals. I confirm you are appropriate for a maximal test before ordering, and if you have a cardiac history, I coordinate with your cardiologist first.
We pick whichever matches your training. Cyclists test on a bike to get watts that map directly to training. Runners test on a treadmill to get pace zones. If you do both, either is fine for a baseline.
6 to 12 months for most patients. Sooner if you are training for a specific event and want to confirm zones have shifted. Annual is sufficient for the longevity-focused use case.
[NEEDS YOUR INPUT: This is typically cash-pay through the performance lab; confirm and note any superbill option. CPET ordered for a cardiac workup may be billable through the cardiologist instead.]
How to order this
Part of the Precision Partnership baseline. Lab fee at vendor cost. I interpret the results into your written Plan.