What is VO2 Max?
Every year our doctors check different parameters of our health. But what if I told you there was a parameter that could predict your overall health, function, longevity, and even all-cause mortality? And that it is not measured as part of a yearly physical. And you have full control on improving it without any medications, supplements, or hacks? Would you believe me? Well, believe me my friends. It exists and it is called a VO2 max. In today’s blog, we are going to learn about VO2 max, why it is important, and how we can control it.
What is VO2 Max?
VO₂ max is the highest rate at which your body can deliver and utilize oxygen during intense exercise. In practical terms, it reflects your cardiorespiratory fitness and how efficiently your lungs, heart, and muscles work together under maximal effort.1-3 It is reported in milliliters of oxygen consumed per kilogram of body weight per minute (mL/kg/min). In order for you to really understand, let’s pause for a brief medical biochemistry lesson.
I’ve mentioned ATP in prior blogs. Our body makes ATP under two separate pathways: one that uses oxygen and one that does not. The pathway that uses oxygen is preferred as it is highly efficient. VO2 max is the rate at which that oxygen is delivered and utilized in the mitochondria for ATP production. When the VO2 max is high, the body can continue to use the oxygen dependent pathway. When it is not, our bodies transition to the lactate pathway for ATP production which only produces 2 molecules of ATP. This pathway also attempts to convert some of the lactate back to glucose. Below is a simplified visual representation of the two processes and how VO2 max relates.
How Is It Measured?
The gold standard measure for performance athletes is a graded exercise test typically done on a treadmill or exercise bike that measures inhaled and exhaled gases through a mask.1 However, there is evidence that the Apple Watch may provide a rough underestimation of VO₂ max levels that is acceptable for general fitness tracking.4
Why Does VO2 Max Matter?
It matters because several studies have linked VO2 max levels to functional independence, longevity, risk of chronic disease, and all-cause mortality.
One of the first questions I ask every patient is “What do you want to be able to do when you are older?” Almost everyone says, “I don’t want to be dependent on anyone and want to be able to take care of myself.” Well, you need a minimum VO2 max of 15 mL/kg/min if you are a woman and 18 mL/kg/min if you are man.5 Functional independence is no longer possible once someone is below these thresholds.
There are several studies that have demonstrated that the higher the VO₂ max, the lower the risk of fatal or nonfatal heart attack. A study of 4808 men and women evaluating the effect of cardiorespiratory fitness on mortality found early-adulthood cardiorespiratory fitness was associated with a lower risk of all-cause mortality and lower risk of nonfatal and fatal cardiovascular events.6 Not in particularly great shape during early-adulthood? Not to worry. A separate study demonstrated that every 1 mL/kg/min increase in VO₂ max was associated with a 9% relative risk reduction of all-cause mortality.7 And even better, a study published in JAMA demonstrated that there is no ceiling effect of mortality benefit for VO₂ max, and cardiorespiratory fitness is a modifiable indicator of long-term mortality.8 Studies demonstrate similar findings when evaluating risk for diabetes, high blood pressure, and high cholesterol.9-15
There is also evidence that some of the hallmarks of aging can be reversed by increasing VO2 max. The most profound effect is on mitochondrial dysfunction. Increasing VO2 max leads to improvements in mitochondrial biogenesis, enzyme activity, and turnover in both young and elderly individuals.16-21 There is also evidence that a higher VO2 max is associated with longer telomere length, lessening the effects of telomere attrition.22 Furthermore, evidence suggests improving mitochondrial function may also mitigate oxidative stress and promote autophagy which impacts the hallmarks of loss of proteostasis and cellular senescence.21,23
How VO2 Max Changes with Age
VO2 max declines with age, so while many of us may feel fit now, it’s important to think not just about our current number but about its trajectory. For example, I am 47 and my current estimated VO2 max is 36.7 (I’m actively working on increasing it by the way). Research suggests VO2 max declines about 8% per decade after 30 and can accelerate to as much as 20% per decade after 50 in sedentary adults.24,25 Using those estimates, by age 50, my VO2 max will be 35.8. At 80, it will be at 19.5, which is still above the threshold associated with maintaining independence. These are averages and not guarantees. The actual trajectory depends heavily on activity level. A sedentary lifestyle accelerates decline, while maintaining or increasing training can significantly flatten the slope. Today’s level of activity greatly influences what your future will look like.
How To Improve Your VO2 Max
I am sure you’ve guessed it by now. Exercise is the key to improving VO2 max, but which exercises and how often? The answer depends on an individual’s baseline fitness level. If someone is “out of shape” or at a low baseline fitness level, working in Zone 2 is a great place to start. Zone 2 is defined as low-intensity exercise below the lactate threshold level.26 It can be measured through the talk test, which states you are in Zone 2 if you can speak but are too out of breath to sing. Heart rate ranges of 55%-75% of one’s maximal heart rate can also be used to estimate Zone 2.2
Individuals at moderate or high levels of fitness will have the highest impact on improving VO2 max with high-intensity interval training (HIIT). Protocols and exact exercise recommendations vary based on age and other comorbidities. Improvements in VO2 max can be seen when exercise is sustained for at least 4 weeks27 and can take up to 30 weeks in older, more sedentary people.28
VO2 Max as a Starting Point
The first data point I want is an individual’s current VO2 max. I prefer obtaining the direct measurement at my office, but I will accept a rough estimate from less accurate personal biometric devices such as an Apple Watch, especially for patients with significant cardiovascular risks where a direct measurement may be too strenuous. This provides me information about each patient’s current VO2 max for their age using the American College of Sports Medicine VO2 max chart. It also provides a baseline level of fitness. With that baseline, I can create individualized exercise plans designed to increase VO2 max and help patients maintain the level of fitness needed to do whatever they want as they get older.
Bottom Line
The information on VO2 max is not only fascinating but encouraging. We can potentially change the course of our health span and rate of biological aging with some exercise. It’s so simple. And no, it is not easy. I’ve said it time and again, I do not enjoy exercising. But my current dislike of exercise doesn’t come close to the feeling of dread and despair I feel at the thought of needing to be dependent on someone because I am too frail or a fall risk when I am older. I’ll put in the work now.
Disclaimer: Even though I’m a doctor, I’m not your doctor—and reading this blog does not establish a doctor–patient relationship. This information is intended for general educational purposes only and should not be taken as personalized medical advice. Always speak with your own healthcare provider before making decisions about your health.
References
- Raghuveer G, Hartz J, Lubans DR, et al. Cardiorespiratory Fitness in Youth: An Important Marker of Health: A Scientific Statement from the American Heart Association. Circulation. 2020;142(7):e101-e118. doi:10.1161/CIR.0000000000000866
- Fletcher GF, Ades PA, Kligfield P, et al. Exercise Standards for Testing and Training: A Scientific Statement From the American Heart Association. Practice Guideline. Circulation. 2013;128(8):873-934. doi:10.1161/CIR.0b013e31829b5b44
- Hunter SK, Angadi SS, Bhargava A, et al. The Biological Basis of Sex Differences in Athletic Performance: Consensus Statement for the American College of Sports Medicine. Translational Journal of the American College of Sports Medicine. 2023;8(4):1-33. doi:10.1249/TJX.0000000000000236
- Lambe R, O’Grady B, Baldwin M, Doherty C. Investigating the accuracy of Apple Watch VO2 max measurements: A validation study. PLoS One. 2025;20(5):e0323741. doi:10.1371/journal.pone.0323741
- Shephard RJ. Maximal oxygen intake and independence in old age. British Journal of Sports Medicine. 2009;43(5):342-346.
- Pettee Gabriel K, Jaeger BC, Lewis CE, et al. Analysis of Cardiorespiratory Fitness in Early Adulthood and Midlife With All-Cause Mortality and Fatal or Nonfatal Cardiovascular Disease. JAMA Network Open. 2023;6(2):e230842-e230842. doi:10.1001/jamanetworkopen.2023.0842
- Laukkanen JA, Zaccardi F, Khan H, Kurl S, Jae SY, Rauramaa R. Long-term Change in Cardiorespiratory Fitness and All-Cause Mortality: A Population-Based Follow-up Study. Mayo Clin Proc. Sep 2016;91(9):1183-8. doi:10.1016/j.mayocp.2016.05.014
- Mandsager K, Harb S, Cremer P, Phelan D, Nissen SE, Jaber W. Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing. JAMA Network Open. 2018;1(6):e183605-e183605. doi:10.1001/jamanetworkopen.2018.3605
- Carnethon MR, Gidding SS, Nehgme R, et al. Cardiorespiratory Fitness in Young Adulthood and the Development of Cardiovascular Disease Risk Factors. JAMA. 2003;290(23):3092-3100. doi:10.1001/jama.290.23.3092
- Williams PT. Vigorous Exercise, Fitness and Incident Hypertension, High Cholesterol, and Diabetes. Medicine and Science in Sports and Exercise. 2008;40(6):998-1006. doi:10.1249/MSS.0b013e31816722a9
- Momma H, Sawada SS, Lee IM, et al. Consistently High Level of Cardiorespiratory Fitness and Incidence of Type 2 Diabetes. Medicine and Science in Sports and Exercise. 2017;49(10):2048-2055. doi:10.1249/MSS.0000000000001319
- Jae SY, Kim HJ, Kunutsor SK, et al. Associations of Cardiorespiratory Fitness With Estimated Remnant Cholesterol and Non-High-Density Lipoprotein Cholesterol in Healthy Men. The American Journal of Cardiology. 2023;186:170-175. doi:10.1016/j.amjcard.2022.09.022
- Hassinen M, Lakka TA, Hakola L, et al. Cardiorespiratory Fitness and Metabolic Syndrome in Older Men and Women: The Dose Responses to Exercise Training (DR’s EXTRA) Study. Diabetes Care. 2010;33(7):1655-1657. doi:10.2337/dc10-0124
- Lovell DI, Stuelcken M, Eagles A. Is Maximal Oxygen Consumption an Appropriate Metric for Metabolic Health? European Journal of Applied Physiology. 2025;doi:10.1007/s00421-025-05875-2
- Holtermann A, Gyntelberg F, Bauman A, Jensen MT. Cardiorespiratory Fitness, Fatness and Incident Diabetes. Diabetes Research and Clinical Practice. 2017;134:113-120. doi:10.1016/j.diabres.2017.10.001
- Broskey NT, Greggio C, Boss A, et al. Skeletal Muscle Mitochondria in the Elderly: Effects of Physical Fitness and Exercise Training. The Journal of Clinical Endocrinology and Metabolism. 2014;99(5):1852-1861. doi:10.1210/jc.2013-3983
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- Rezaei A, Bhat SG, Cheng CH, et al. Age-Related Changes in Gait, Balance, and Strength Parameters: A Cross-Sectional Study. PloS One. 2024;19(10):e0310764. doi:10.1371/journal.pone.0310764
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