What is my cardio fitness score?

VO2 Max is a measurement of how well your body uses oxygen when you’re working out at your hardest. It is widely accepted as the gold standard for grading cardiovascular fitness: the higher your VO2 Max, the more fit you are (source). This metric can also indicate performance potential for endurance-based activities including running, biking, and swimming (source).

VO2 Max is traditionally measured in a lab where you run on a treadmill or ride a stationary bike until exhaustion with a mask strapped to your nose and mouth to gauge the amount of air you inhale and exhale. While this method provides the most accurate measure of VO2 Max, your Fitbit device can estimate this value for you with less effort and discomfort.

Fitbit estimates your VO2 Max and refers to it as your cardio fitness score.

Your cardio fitness score is determined by your resting heart rate, age, sex, weight, and other personal information. For best results, make sure your weight is correct in your Fitbit profile. Also, wear your tracker or watch to sleep for a better resting heart rate estimate. Your cardio fitness score will be shown as a range unless you use GPS for runs.

If your Fitbit device connects to GPS, we can provide a more precise estimate of your score using the relationship between pace and heart rate during your runs. This is because individuals with higher VO2 Max have a lower heart rate while running at the same pace compared to individuals with lower VO2 Max. If you're able to run at a comfortable pace for at least 10 minutes, track a run with GPS. We recommend running on flat terrain as much as possible since only the flat sections of your run count toward your score estimate. You may need to go on several runs that are at least 10 minutes in length to affect your score.

For instructions on how to start in the Exercise app, check How do I track my workouts with my Fitbit device?

We use your cardio fitness score in combination with your sex and age to calculate your cardio fitness level. By helping you understand how you compare to other people who share your sex and age range, cardio fitness level is a holistic way to track your cardiovascular fitness over time.

Your cardio fitness score will fall into 1 of 6 cardio fitness levels that range from poor to excellent. These levels are based on published data that help show how your cardio fitness score compares to others who are the same age range and sex (source).

If your cardio fitness level is lower than you’d like, it may be due to several factors including a stationary lifestyle, which could have negative effects on long term health like an increased risk for developing high blood pressure and coronary heart disease (source).

The two ways to improve your score are exercise and healthy weight loss. Increased exercise may help you improve your score by up to 20 percent over a period of two to three months (check Kennedy, Phys. of Sport and Exer., 2012). Specifically, the American Heart Association recommends “at least 150 minutes per week of moderate exercise or 75 minutes per week of vigorous exercise (or a combination of moderate and vigorous activity)” to improve overall cardiovascular health (source).

While an increase in moderate exercise can be helpful, including high-intensity intervals in your workouts if you’re able can be an effective way to check noticeable improvement. Interval training includes any workout that alternates between intense bursts of activity followed by periods of lower intensity activity or rest. Both endurance training and interval training studies showed increases in participants’ VO2 Max, but interval training yielded more significant improvements (source). For more information on how to use intervals in your workout, check How do I track my workouts with my Fitbit device?

Additionally, healthy weight loss (primarily by lowering your body fat percentage) can contribute to an increase in your cardio fitness score. On the other hand, unhealthy weight loss (lowering your muscle mass) can have a negative effect on your score (source). If you’ve entered a healthy weight loss goal into your Fitbit profile, the graph shows the potential improvement to your score. If your weight loss goal would lower your Body Mass Index (BMI) into the underweight range, potential improvement to your score won’t be displayed. For more information about BMI ranges, check the American Heart Association.

If you're running with GPS, try the following tips for the best estimate:

• Go for long runs (at least 10 minutes long) on flat terrain.
• Complete multiple runs to help improve accuracy.
• Run at a faster pace if you’re able to do so. You don’t have to run at maximum speed but higher-intensity runs provide a more accurate estimate.

To check your cardio fitness score and cardio fitness level on certain Fitbit devices, swipe up on the clock face to open Fitbit Today. Swipe left on the heart rate tile to check your cardio fitness stats.

If your Fitbit device doesn't show your cardio fitness stats, you can check your stats in the Fitbit app.

If you don't check your cardio fitness stats in Fitbit Today, try these tips:

• Wear your device for at least 1 to 2 days. For best results, wear your device to sleep for a better resting heart rate estimate.
• Complete multiple GPS runs for a run-based measurement of your score.
• Wear your device correctly while on a GPS run. Check the troubleshooting tips in What factors can affect my heart-rate reading on my Fitbit device?