James Hewitt
3.5 minutes

What is V̇O₂ max., and why does it matter for everyone?

V̇O₂ max. is a critical measure of our body’s cardiorespiratory health, linked with longevity and quality of life. While certain declines in V̇O₂ max. are inevitable with age, effective training methods like HIIT and LSD can enhance it. With advancements in technology, accurately measuring V̇O₂ max. is more accessible than ever. Learn about the significance of V̇O₂ max, how to measure it, and strategies to boost it for wellbeing and performance.

If you’ve been reading my blog for any length of time, you’ll know that I’m a passionate advocate for maintaining and improving V̇O₂ max. V̇O₂ max. represents our body’s ability to take up & use oxygen. In many ways, it reflects overall physical health as it represents the outcome of many critical physiological systems working together. A recent study adds weight to this claim based on a meta-analysis of 37 cohort studies involving 2,258,029 participants. Being in the top 1/3 of cardiorespiratory fitness decreased the risk of death by 45% compared to being in the bottom 1/3. 

The study also indicates that increasing your V̇O₂ max by just 3.5 ml/kg/min could cut your risk of death by 11%.

VO2 max. may even predict when we will no longer be able to live independently in later life.  For example, someone in the 10th percentile for VO2 max. could expect to begin relying on other people due to reduced physical capacity in their early 70s. In contrast, someone in the 90th percentile could expect to remain independent for the rest of their life.

How can you measure V̇O₂ max.?

There are several ways to measure V̇O₂ max. The most accurate measurement requires a physical effort that is both long and intense enough to tax the aerobic energy system fully. This typically involves visiting a laboratory to endure a graded exercise test where exercise intensity is progressively increased. During this test, breathing rate and depth are measured along with the inhaled and exhaled air’s oxygen and carbon dioxide concentration. This is often done using a cardiopulmonary exercise test (CPX test) on a treadmill or cycle ergometer. However, there are also several ways to estimate V̇O₂ max., which don’t require a trip to the lab.


A recent study indicates that, for runners with a V̇O₂ max between 44 mL/kg/min and 55 mL/kg/min, Garmin wearables achieved a mean absolute percentage error of just 4.1% for Vo2Max estimation, relative to laboratory tests. However, accuracy was worse for participants with a V̇O₂ max, below or above this range.

Other wearable devices, such as the Firstbeat Bodyguard, can also provide reasonable estimations of V̇O₂ max. simply by wearing the device during regular walking and exercise. The error was below 3.5 ml/kg/min, evenly distributed around the mean value in most measurements.

Apple Watch:

Any Apple Watch from Series 3 onwards received an updated algorithm to estimate the user’s V̇O₂ max. providing the device features the WatchOS 7 software or later. The estimation is based on measuring the user’s heart rate response to physical activity. Updates to the algorithm extended estimates to lower ranges of V̇O₂ max. (14 to 60 ml/kg/min). Apple’s internal validation studies indicate that the V̇O₂ max. estimation method is accurate and reliable relative to commonly used techniques, with an average error of less than 1 MET (3.5 ml/kg/min).

What is a ‘good’ V̇O₂ max. for my age?

Once you’ve measured or estimated your V̇O₂ max., many people’s next question relates to understanding how they compare to others and whether there are standards to indicate what ‘good’ looks like. Several studies have examined this question. I’ve summarised the results of one study in the tables below. All values are expressed in ml/kg/min.

How can you improve V̇O₂ max.?

V̇O₂ max. can be improved in several ways. I’m providing some ideas below for informational purposes, but before you begin any exercise program, you should consult an appropriately qualified professional. Entire books have been written about the best way to improve V̇O₂ max., but it basically boils down to two complimentary methods. Most of your training should be Long and Slow, over extended Distances (LSD). A small amount should be based around High-Intensity Interval Training (HIIT).

Long, Slow Distance Training (LSD)


  • Percentage of Maximum Heart Rate (MHR): LSD workouts are typically performed at 60-75% of MHR.
  • Rate of Perceived Exertion (RPE): On the RPE scale, LSD workouts usually fall in the 4-6 range, representing a comfortable and sustainable effort.
  • As a rule of thumb, you should be able to speak in a complete sentence at this intensity, without taking a breath, but only just.


  • The length of LSD workouts can vary based on the individual’s fitness level and training goals. This might be a 30-minute continuous jog for beginners, while more advanced athletes might go for runs lasting 90 minutes to 2 hours or even longer.


  • LSD workouts can be done more frequently than HIIT due to their lower intensity. Depending on the individual’s training plan and goals, LSD sessions could be performed 3-5 times weekly.

High-Intensity Interval Training (HIIT)


  • Percentage of Maximum Heart Rate (MHR): Typically, HIIT sessions involve working at 85-95% of MHR during high-intensity intervals.
  • Rate of Perceived Exertion (RPE): On a scale of 1 to 10 (with 10 being the maximum effort), HIIT intervals often fall in the 8-10 range.


  • Intervals: The length of the high-intensity intervals can vary widely, from as short as 20 seconds to as long as 4 minutes. Common formats include 30 seconds of work followed by 30 seconds of rest or 4 minutes of work followed by 4 minutes of rest.
  • Total Session: A typical HIIT session, including warm-up, intervals, and cool-down, might last anywhere from 20 to 45 minutes.


  • Due to the intense nature of HIIT, most people should complete these workouts a maximum of 1 or 2 times per week, ensuring adequate recovery time between sessions. Also, people who have done little to no exercise or who are unfamiliar with high-intensity exercise should cautiously build up to completing HIIT under the instruction of an appropriately qualified professional.

Are declines in V̇O₂ max. inevitable?

The short answer is yes, but not as much as we once thought. Changes in training volume explain >50% of the reductions in V̇O₂ max. seen in athletes as they age. I.e., training less as we get older may be one of the most significant contributors to declines in cardiorespiratory fitness. Also, even if V̇O₂ max has decreased through reduced training, it can bounce back quickly. V̇O₂ max. increases of 9–13% were observed after eight weeks of high-intensity interval training (HIIT) in men & women aged 20 to 70+.

Hopefully, this blog has answered a few common questions about V̇O₂ max., why it matters, what is a ‘good’ V̇O₂ max., and how you can improve it!

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