Especially for athletes, VO2 Max is a metric of key importance for cardiovascular fitness. Many smartwatches, such as the Apple Watch, give estimates of VO2 max based on heart rate and pace. But if you’re someone like me who is generally working towards a healthy lifestyle, this measurement can be quite confusing and, at times, discouraging.
So, when I started focusing on my Apple Watch, giving me a lower VO2 max, not only did I get concerned, but I set out on my personal research to find if this number was accurate and if I needed some serious TLC or if this was just a fluke.
What the studies say:
- A study by JMIR Publications found out that the Apple Watch underestimated VO₂ max with a high mean absolute percentage error of 15.79%, indicating that there is a noticeable difference from lab measurements.
- Another study by West Texas A&M University concluded that the Apple Watch’s VO₂ max estimates were not very different from VO₂MasterPro measurements; however, they had a very weak correlation (r=0.2), indicating poor agreement.
- The same study also concluded that the Apple Watch overestimated VO₂ max by an average of 6 mL/kg/min in six cases but underestimated it by 10.4 mL/kg/min in ten cases, and when analysed by sex, Apple’s estimates were fairly accurate for males but not for females.
How the Apple Watch measures VO2 Max
Simply put, VO2 max is the maximum oxygen consumed by us during an intense exercise. This is a great indicator of the cardiovascular health of an individual. Some health experts even swear by this indicator.
While normally, it is calculated in millilitres of oxygen a minute per kilogram of body weight, the Apple Watch uses heart rate and motion sensors during a workout like an Outdoor Walk, Outdoor Run, or Hiking on the Workout app on Apple Watch. This metric can be calculated using any Apple Watch Series 3 or later.
The Apple Watch also takes into consideration my personal data, such as age, weight, gender, height, and any medications I take that can affect my heart rate.
My experience with the Apple Watch’s VO2 Max:
Judging by medical grade accuracy, the Apple Watch is just not it. This not only gave me some peace of mind and relief, but it also made it more concrete that fitness devices are not to be blindly followed. But I wasn’t done here; I tested out my VO2 max while doing workouts with my Apple Watch for a period of time to see if it improves or should I just stop bothering about this number altogether.
At first, the VO2 max was seriously low, and I couldn’t fathom why. I’m not a fan of cardio, but I do get through a HIIT workout without feeling like I wanna die. So there was my first indication that the number being displayed on my Health app was not correct.
But I wasn’t letting intuition lead the way, so I thought of training more and including more cardio in my rotation. Now, that would help me get this number up, right? Wrong! Not only was my Apple Watch underestimating my VO2 max, but it was going further down even after all that training.
According to my Apple Watch, my VO2 max was 28.6, which is considered ‘low.’ After several days of incorporating cardio into my gym routine, my VO2 max came down to 27.1, while in theory, it should’ve increased.
Although I have seen people test the Apple Watch’s VO2 max with a treadmill test and the results were pretty close. However, it is important to understand that the VO2 max data is only calculated by the Apple Watch with 20+ minutes of uninterrupted outdoor workouts.
So if my Apple Watch misses a reading because of its fit or I stop in the middle of my workout to play with a dog or something, that is going to affect my VO2 max reading. Not to say I’m way healthier than what my Apple Watch suggests, but I’m sure it is giving me a ballpark figure of my VO2 max, not the actual reading.
How to improve the accuracy of VO2 max readings on the Apple Watch
Even if it’s a ballpark figure, to get the most out of your Apple Watch’s VO2 max readings:
- Make sure the watch is snug on your wrist and not loose.
- Regularly update your personal data on your Health app.
- Make sure to pause your workouts on the Apple Watch whenever you take a break.
- Make sure to stop the workouts on the Apple Watch as soon as your main workout is over, right before cool down and stretching.
- Recalibrate your Apple Watch regularly for the most accurate readings.
- Make sure to check that you haven’t added any medications that can affect your heart rate if that is not the case.
To check this, head to Watch > Health > Health Details > Medications That Affect Heart Rate > if it is 0, it means there are no medications added.
Wrap Up
As with any other metrics that are only accurately measured using lab tests as a gold standard, Apple Watch gives a ballpark estimate and shouldn’t be taken too literally. However, these are good for the general upkeep of your health.
Personally, I have strived to get my Apple Watch’s VO2 max graph to go higher, but maybe it’s the breaks I take between my workouts that are not giving me the desired results. For an accurate test, though, a lab test is required.
