I recently decided to put my fitness to the test by taking a short but intense assessment. To my disappointment, the results didn’t show what I had hoped for. Nevertheless, this experience has shed light on the significance of monitoring my physical activity.
In the past, I’ve always engaged in regular exercise without actually keeping track of my workouts. However, this year I acquired an Apple Watch, and suddenly I found myself immersed in a world of detailed statistics regarding my daily physical exertion. These numbers have become an obsession of mine.
Among the many metrics that the Apple Watch tracks is my estimated VO2 max. This metric represents the maximum amount of oxygen that one can consume during intense exercise. Widely considered by health experts as the most reliable indicator of cardiovascular fitness, research has even shown that it correlates with longevity. In fact, the American Heart Association emphasizes that fitness level should be treated as a vital sign.
VO2 max is measured in milliliters of oxygen per minute per kilogram of body weight. Determining your true VO2 max requires intense exercise while wearing an oxygen mask that measures oxygen consumption. Essentially, the more oxygen you burn, the higher your level of fitness.
While the Apple Watch doesn’t have an integrated oxygen mask, it utilizes multiple data points such as heart rate, weight, age, and walking or running speed to provide an estimate of your VO2 max. According to my watch, my VO2 max stands at 39.4, which it classifies as high for someone my age (66 years old). As higher values indicate better fitness, I’m pleased with this result.
To put this into perspective, a resting person typically consumes 3.5 milliliters of oxygen per kilogram, as measured by a MET (metabolic equivalent). According to my Apple Watch score, I have the capacity to burn nearly 11.2 times that amount, equivalent to 11.2 METs. The greater the number of METs you can burn, the higher your level of fitness. Apple claims that, on average, its estimates are accurate within one MET.
So, armed with my Apple Watch, I have become increasingly aware of the importance of monitoring my fitness. It has not only provided me with valuable insights into my current state of health but has also motivated me to strive for continuous improvement.
Testing the Apple Watch’s Accuracy
I should have stopped there, but I didn’t. I wanted to test out the Apple Watch’s accuracy. So I took an actual VO2 max test at a local sports medicine center for $200. No, insurance didn’t cover it.
Pushing My Limits
The woman administering the test attached EKG clips to my chest, put a mask over my face, and told me to walk on a treadmill. She gradually increased the speed to five miles an hour, and then she began increasing the incline. I lasted 11 minutes, until it was at a 12% slope. I could have gone another minute if I really needed to, but it was getting hard. My legs still felt tired hours later.
The Surprising Results
I thought I had done well. True confession: Vain man that I am, I also was hoping my measured VO2 max would be even better than Apple’s estimated score.
But the test isn’t just measuring effort, it is measuring how high your oxygen consumption goes before it plateaus. Mine stopped rising at 34.6 milliliters per kilogram of weight, below the 39.4 score estimated by my watch.
Whereas I was hoping my Apple Watch had underestimated my fitness, it had actually overestimated it by roughly 1.3 METs. That is a bit more than the average error cited by Apple, but still in the ballpark.
A Reality Check
Bottom line: My fitness level is above average, but it’s nothing stellar either. According to the Marathoner handbook table, I’m in the 75th percentile for my age. That means I’m in good health (knock on wood), but my fitness is way below the levels of a competitive endurance athlete my age.
Oh, well. Easy come, easy go.