Once reserved for elite athletes, VO2 max testing is now available to everyday fitness enthusiasts thanks to smartwatches. This measurement, which assesses aerobic fitness, was traditionally conducted in labs by trained professionals. However, advancements in technology have made it easier for users to estimate their VO2 max at home.

VO2 max refers to the maximum volume of oxygen that the body can utilize during intense exercise. It is typically expressed in milliliters of oxygen per kilogram of body weight per minute. For middle-aged men, the average VO2 max ranges from 32 to 38 ml/kg/min, while for women, it is between 28 and 33 ml/kg/min. A higher VO2 max indicates a greater ability to sustain energy during workouts.

In a lab setting, VO2 max is measured by having individuals run on a treadmill or pedal a stationary bike while wearing a heart rate monitor and a mask. As the intensity of the exercise increases, lab personnel monitor oxygen consumption and carbon dioxide output until the individual reaches exhaustion.

Elite endurance athletes, such as cross-country skiers and cyclists, often have the highest VO2 max scores. For instance, an 18-year-old cyclist from Norway recorded an impressive VO2 max of 97.5. Factors such as age, body weight, height, and sex influence VO2 max scores. Generally, men tend to have higher scores due to greater muscle mass, while age is associated with a decline in VO2 max due to metabolic slowdowns. Larger body sizes also require more effort to deliver oxygen to muscles.

VO2 max is not only a fitness metric but also an important indicator of cardiovascular health. Research shows that a higher VO2 max correlates with a lower risk of heart disease. Smartwatches estimate VO2 max by using built-in sensors to track heart rate and movement, along with user-provided data such as age, height, weight, and sex.

Users may notice fluctuations in their VO2 max scores displayed on their smartwatches. These changes can occur due to variations in workout frequency and intensity. A decrease in exercise can lead to a lower score, while increased activity may result in an improvement. However, it is important to remember that smartwatch calculations are estimates. Most brands do not disclose the algorithms used, making it difficult to understand how scores are derived.

Studies comparing smartwatch estimates with lab tests have shown that smartwatches often underestimate VO2 max in highly fit individuals and overestimate it in those with lower fitness levels. Additionally, changes in the algorithms used by smartwatches can disrupt the consistency of historical and current scores, leading to unexpected fluctuations.

Recovery and sleep also play crucial roles in maintaining or improving VO2 max. Elite athletes may experience a drop in their scores despite increased training intensity due to fatigue. Coaches often monitor VO2 max to determine if athletes need more rest rather than additional exercise.

While a high VO2 max is beneficial, it does not guarantee superior athletic performance. Other factors, including physiological, biomechanical, and psychological elements, also contribute to success in sports. Nevertheless, many top endurance athletes possess impressive VO2 max scores, often influenced by genetic factors.

For recreational athletes, tracking VO2 max serves as a health assessment tool. Smartwatches categorize VO2 max as high, above average, below average, or low, encouraging users to aim for an average or above-average rating. To enhance VO2 max, incorporating high-intensity exercises into workout routines is recommended. While long, steady workouts build endurance, pushing the body into higher intensity zones is essential for improving aerobic fitness.

With the rise of smartwatches, VO2 max tracking has become accessible to a broader audience, providing an additional means to monitor health and fitness levels.