Many fitness vo2 max monitor  and sports watches now estimate your VO2 max, and the trend of increasing accuracy over time means it’s a useful feature. It helps you understand how fit you are, and it also provides motivation to continue to work on your fitness and see results in the form of a higher VO2 max.

VO2 max is a measure of your aerobic system’s capacity to take in and use oxygen at maximum exertion during intense exercise. It’s a complex figure that correlates with many other factors, including health benefits and cognitive function (though correlation does not establish causation).

Maximize Your Workouts: The Top VO2 Max Monitors for Precision Fitness Tracking

There are multiple ways to calculate your VO2 max, and while most of them can be done at home, the only way to get an accurate number is through lab testing. Fortunately, there are several gyms and holistic health clinics that offer VO2 max testing as a part of their membership or services. For example, TriFitLA in Los Angeles, California offers VO2 testing with several other performance and fitness tests.

Most smartwatches that include a VO2 max monitor use a variety of data to estimate your score, including your gender, age, GPS activity for speed and steps, heart rate, and resting heart rate. The most accurate smartwatches are those that use a chest strap heart rate monitor, because wrist-based optical sensors can be inaccurate and lead to over or underestimating your VO2 max estimate.

Garmin’s VO2 max estimates are available on most of its sports watches and running watches, including the Forerunner series starting at 245 and up and the Coros line of sports watches. The Apple Watch and the Google Pixel Watch also offer a VO2 max estimate, called your Fitness Level or Cardio Fitness Score, based on outdoor runs.