A VO₂max test can produce an impressive report: maximal oxygen consumption, heart rate, ventilation, pace or power, training zones and several graphs. The difficult part is deciding what numbers are important, which are just data, and which if any you should be using to guide your training.
For fitness and longevity, the highest number is only one part of the result. VO₂max describes the upper limit of your aerobic system, while your ventilatory thresholds, and lactate thresholds, show how much of that capacity you can use at sustainable intensities. Together, they help distinguish easy aerobic work, moderately demanding exercise and genuinely hard intervals.
This article explains how to read those results and turn them into a practical training plan.
It will not go deeply into the oxygen-transport physiology behind VO₂max; that will be covered in depth in future resources.
What Is VO₂max?
VO₂max is the highest rate at which your body can take in, transport and use oxygen during intense exercise. It is an integrated measure of cardiorespiratory fitness: your lungs, heart, circulation and working muscles all contribute to the final result.
VO₂max is usually reported in two ways:
Absolute VO₂max, measured in litres of oxygen per minute (L/min), describes your total oxygen-using capacity.
Relative VO₂max, measured in millilitres of oxygen per kilogram of body mass per minute (mL/kg/min), divides that capacity by body weight. This is the number most often used to compare people or place a result within age- and sex-based reference values.
Relative VO₂max is useful, but the denominator matters- it is relative to your entire body mass. Losing body fat can raise the relative value even if absolute oxygen consumption is unchanged and gaining muscle can have the opposite effect (if it is not accompanied by increases in aerobic fitness). I prefer to interpret both values alongside body composition and the exercise modality used.
Furthermore, treadmill and cycling results should not be compared as if they were interchangeable. Running typically recruits more total muscle mass and often produces a higher VO₂max than cycling. Also, you are going to be able to reach higher numbers in the modality that you are more comfortable with. This means for a runner like me, there is going to be a large gap between my running and bike numbers, because I am much more comfortable running hard than cycling hard, and it uses more muscle mass. Large reference datasets therefore publish separate norms for treadmill and cycle testing.
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A direct graded test measures breathing and oxygen use as workload increases. A smartwatch estimates VO₂max from variables such as heart rate, speed and profile data. Estimates from things like watches can help track trends, but they are not equivalent to direct measurement. Watch based estimates have too many confounding variables such as weather, terrain, accuracy of heart rate data, GPS accuracy, topography and elevation, etc.
Next, interpret the result in context:
Use appropriate reference data. Age, sex and test modality affect the expected range. A percentile describes your position within a reference population; it is not a diagnosis.
Consider whether the effort was maximal. If local fatigue, mask discomfort or unfamiliarity with the equipment ended the test, the highest observed value may be better called VO₂peak. It remains useful, but the limitation matters.
Look beyond one score. Cardiorespiratory fitness is strongly associated with long-term health outcomes, but blood pressure, metabolic health, strength, body composition, symptoms and medical history still matter.
Use the first test as a baseline. Ask what you should train and whether your fitness improves over time—not simply whether the number is “good” or “bad.”
A high VO₂max is valuable physiological reserve, but two people with the same value can have very different capacities for sustained exercise because their thresholds occur at different fractions of that maximum. Therefore, knowing your VO₂max is a very useful data point when it comes to understanding your overall health and performance capacity, but it is only one data point. An expert in the interpretation of exercise physiology data can help walk you through what other measures you should also be focused on in addition to your VO₂max.
LT1 and VT1: Your First Exercise Threshold
The terminology around thresholds is unnecessarily confusing, so an important distinction comes first.
Lactate thresholds are identified from blood lactate; ventilatory thresholds come from breathing and respiratory data. LT1 and VT1 often occur near one another, as do LT2 and VT2, they are not identical measurements, but can generally be used interchangeably.
In a VO₂max assessment that does not collect blood samples, the directly assessed points are VT1 and VT2. They can provide practical estimates of the intensity domains commonly discussed using LT1 and LT2, but it is more accurate to report them as ventilatory thresholds. Because we generally use heart rate at a given threshold, and it is more of a range than a specific number, this distinction matters very little in the real world outside of hyper-elite athletes.
VT1 is the first clear transition in your breathing response as exercise becomes progressively harder. It broadly separates the moderate-intensity domain from the heavy-intensity domain.
Below VT1, oxygen consumption and lactate settle into a steady state. The effort should feel controlled, breathing is rhythmic, and conversation is possible in full sentences. This is where most people can accumulate aerobic training with relatively manageable fatigue.
That makes VT1 a useful upper anchor for easy aerobic sessions. It is often close to what coaches mean by “easy,” “aerobic base” or “Zone 2,” although zone terminology varies between three-, five- and seven-zone systems. Your watch’s Zone 2 is not necessarily the same as exercising below your measured VT1, as companies use their own algorithms to calculate these zones, and we have already discussed the general inaccuracy of watch estimates.
VT1 is not a razor-thin boundary. Your physiology does not transform one beat above the reported heart rate- it is a gradual transition between energy systems. This is why understanding the heart rate, work rate and perceived level of exertion at these thresholds is more accurate, as any one of those variables can change day to day.
LT2 and VT2: Your Second Exercise Threshold
VT2 is the second major change in the ventilatory response. It broadly marks the transition from the heavy-intensity domain into the severe-intensity domain. It is also called the respiratory compensation point in some testing systems.
Between VT1 and VT2, exercise is demanding but oxygen consumptions and lactate production can still reach a delayed steady state at appropriate workloads. Breathing is deeper, conversation is limited to a few words at a time and fatigue accumulates faster. However, breathing and mechanics are still under control in this training range. Sessions here may be described as steady, tempo or sub-threshold training.
At and above VT2, the effort becomes much less sustainable. Breathing rises disproportionately, talking becomes uncomfortable, and oxygen consumption may move toward VO₂max. This domain is useful for hard intervals, but it produces substantially more fatigue.
LT2 is sometimes described as the point where lactate suddenly “goes anaerobic” or where the body stops using oxygen. Neither description is accurate. Aerobic and anaerobic energy systems are always contributing; their relative contributions change continuously as intensity increases. Thresholds are useful transition markers, not metabolic on-off switches. LT2 is the point where lactate production is no longer at a steady state, not the point where you switch completely from using oxygen to producing lactate.
Turning VT1 and VT2 Into Training Zones
The cleanest way to use the thresholds is to start with three physiological intensity domains rather than forcing the results into a particular commercial zone system.
These descriptions are deliberately broad. Threshold heart rate, speed and power depend on the testing method, and a workload observed during a rapid graded test may not be sustainable during a longer constant-intensity workout.
How to Use Your Results in a Training Plan
1. Anchor easy aerobic work below VT1
For general fitness and longevity, the bulk of cardiovascular training should be repeatable and recoverable. Use VT1 heart rate as an upper guide, not a target you must constantly touch.
Heart rate rises gradually at the beginning of a workout and may drift upward during longer exercise because of heat, dehydration and fatigue. Use pace or power, breathing and perceived effort alongside heart rate. If the same pace suddenly requires a much higher heart rate and feels harder than usual, forcing the planned number may be counterproductive.
Using VT1 as the upper anchor ensures that you are still gaining some cardiovascular adaptation from your exercise, but not overloading your legs for your next lifting day or disproportionately increasing your risk of injury.
2. Use the middle domain deliberately
Training between VT1 and VT2 is not a forbidden “grey zone.” It is useful for tempo sessions and longer intervals. The problem arises when easy days repeatedly drift into this range, creating more fatigue without the focus of a planned quality workout.
Overusing this domain is going to limit how fast you recover from your longer runs, and significantly increase your risk of injury if you complete too much volume in this zone by just "grinding it out".
3. Reserve work near or above VT2 for focused sessions
Intervals around VT2 can develop sustainable high-end aerobic capacity, while shorter intervals above VT2 can stimulate VO₂max. Neither needs to dominate the week. The right combination depends on training history, injury tolerance, goals and recovery.
These workouts need to be deliberately positioned in your week because they are going to require dedicated recovery time. They are great workouts because they are very physiologically demanding, but they are also dangerous in terms of overdoing them for the same reason. Build them in intelligently, and they can really add rocket fuel to your workout program.
4. Build the week around consistency
A practical starting week for a generally healthy adult combining cardiovascular and strength training might look like this:
Monday: Full-body strength training
Tuesday: 35–50 minutes below VT1
Wednesday: Rest, walking or mobility
Thursday: Full-body strength training
Friday: One focused cardiovascular session—either intervals between VT1 and VT2 or shorter intervals above VT2
The relationship between the measurements can be more informative than any number alone.
Lower VO₂max with proportionate thresholds: Improving overall aerobic capacity may be the main priority.
Reasonable VO₂max but a relatively early VT1: More consistent low-intensity aerobic volume may help improve sustainable capacity.
Strong VT1 but limited high-intensity capacity: A carefully introduced interval block may be useful if health, training history and musculoskeletal tolerance allow it.
Good laboratory numbers but poor real-world tolerance: The limitation may involve strength, movement economy, pain, fuelling, heat tolerance or the demands of a specific activity—not aerobic capacity alone.
These patterns generate hypotheses, not automatic prescriptions. A report should be interpreted alongside your goals and the type of exercise you actually perform.
When Should You Retest?
If you are following a focused training block, retesting after approximately 8–16 weeks can be reasonable. For general health monitoring without a major change in training, testing every 6–12 months is often sufficient.
Retesting should use the same exercise modality and a comparable protocol whenever possible. Similar sleep, fuelling, hydration, medication timing and recent training load also improve the comparison. Do not focus only on VO₂max: changes in heart rate, pace or power at VT1 and VT2 may show meaningful improvement even when the maximal value changes little.
Small changes should be interpreted cautiously because biological and measurement variability cannot be eliminated. A trend across repeated, well-standardized tests is more persuasive than a minor difference between two isolated results.
The Bottom Line
A VO₂max test should do more than tell you whether your aerobic fitness is above or below average. It should help answer three practical questions:
What is the current ceiling of my aerobic system?
Where do easy, moderate and hard exercise begin for me?
How should those intensities be distributed in my training?
VO₂max describes your maximal aerobic capacity. VT1 helps anchor sustainable aerobic work. VT2 helps define the transition toward high-intensity exercise. Used together, and interpreted as ranges rather than magical cut-offs, they can make training more individualized, purposeful and easier to evaluate over time.
A maximal exercise test is not appropriate for everyone. New or unexplained chest pain, fainting, marked breathlessness, palpitations with exercise or other medical concerns should be assessed before maximal testing or high-intensity training. This article provides general educational information and is not a substitute for individualized medical advice.
References
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Kaminsky LA, Arena R, Myers J, et al. Updated Reference Standards for Cardiorespiratory Fitness Measured With Cardiopulmonary Exercise Testing: Data From the FRIEND Registry. Mayo Clinic Proceedings. 2022;97(2):285–293. https://pubmed.ncbi.nlm.nih.gov/34809986/
Jamnick NA, Pettitt RW, Granata C, Pyne DB, Bishop DJ. An Examination and Critique of Current Methods to Determine Exercise Intensity. Sports Medicine. 2020;50:1729–1756. https://pubmed.ncbi.nlm.nih.gov/32729096/
Cerezuela-Espejo V, Courel-Ibáñez J, Morán-Navarro R, Martínez-Cava A, Pallarés JG. The Relationship Between Lactate and Ventilatory Thresholds in Runners: Validity and Reliability of Exercise Test Performance Parameters. Frontiers in Physiology. 2018;9:1320. https://doi.org/10.3389/fphys.2018.01320
Anselmi F, Cavigli L, Pagliaro A, et al. The Importance of Ventilatory Thresholds to Define Aerobic Exercise Intensity in Cardiac Patients and Healthy Subjects. Scandinavian Journal of Medicine & Science in Sports. 2021;31(9):1796–1808. https://doi.org/10.1111/sms.14007
Milanović Z, Sporiš G, Weston M. Effectiveness of High-Intensity Interval Training and Continuous Endurance Training for VO₂max Improvements in Healthy Adults: A Systematic Review and Meta-Analysis of Controlled Trials. Sports Medicine. 2015;45:1469–1481. https://pubmed.ncbi.nlm.nih.gov/26243014/
