What Good Are Wearable Computers if the Data Is Wrong?

Smartwatches from tech companies like Apple and Garmin make it easy to see a number that could reflect how old you are more accurately than your age: the VO2max, the maximum amount of oxygen that your body can use during intense exercise.

The higher your VO2max, exercise experts say, the better your cardiovascular fitness and, potentially, the longer your life. In the past, only serious athletes sought a traditional VO2max test, which involved wearing cumbersome sensors while exercising inside a lab, but now anyone can get an estimate by wearing a smartwatch and moving around.

Is it good to have access to this kind of information? And how accurate could a wearable be? In the last five months, when I fell down a VO2max rabbit hole, I learned some uncomfortable truths about my health and the limits of smartwatches.

First, let me tell you about my fitness journey. In November, while I was out celebrating my birthday, my Apple Watch delivered the most unwanted gift: a notification of a high heart rate. That led me to look at my VO2max, which the Apple Watch said was 32, well below average for a man in his late 30s.

In search of a quick solution, I bought a membership at a high-intensity interval gym, a type of training that specializes in boosting cardio fitness. Five months and many kettlebell swings and jump squats later, I felt progress. I burned fat, gained muscle and felt more energetic. The Apple Watch gave me a VO2max estimate of 40, just shy of average, and a Garmin watch that I also wore rated me at 45.

All that was left to do was to take a real VO2max test, so I found one. This is where the good news ends. A few hours after pedaling on an exercise bike with an oxygen mask strapped to my face, I got my lab results: 25, a rating of poor, far below the flattering results from the Apple Watch and Garmin. Devastating.