Cardiorespiratory fitness

A clinical vital sign for a long and healthy life

The PAI Health app guides you to improve your cardiorespiratory fitness (CRF) for maximum protection from cardiovascular disease, showing you the heart health impact of physical activity.

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Why is CRF important?

Cardiorespiratory fitness (CRF) measures how well your body is able to transport and utilize oxygen during any sustained physical activity. The primary measure of CRF is VO2 max.

Good CRF is not only important for your overall health and quality of life, such as your energy levels, sleep, and mood, but it also reduces the risk of heart disease, diabetes, strokes, and other lifestyle diseases.


Both the American Heart Association and British Journal of Sports Medicine advocate CRF as a clinical vital sign that should be routinely assessed.

A growing body of evidence demonstrates that CRF is a potentially stronger predictor of mortality than established risk factors such as smoking, hypertension, high cholesterol, and type 2 diabetes.

American Heart Association

CRF was more strongly associated with all-cause mortality than physical activity.

British Journal of Sports Medicine

Are you as fit as you think you are?

For a long-term view of your cardiorespiratory fitness level, the Cardiac Exercise Research Group at the Norwegian University of Science and Technology developed the Fitness Age Calculator.

Your Fitness Age is an estimate of your CRF (also known as your VO2 max) as it compares to other adults of your age and sex. You can take the free online Fitness Calculator by clicking the button below, or get your Fitness Age assessed by signing up for the PAI Health app.

Think of your Fitness Age like your overall CRF report card, while PAI is your lesson plan to improve it — by consistently maintaining 100 PAI or more over sustained periods of time, you may be able to improve (lower) your Fitness Age.

Calculate my Fitness Age

PAI reduces cardiovascular disease mortality risk for everyone

Studies have shown that earning 100 or more PAI is associated with reducing the risk of cardiovascular disease mortality on average by 25%, and adding up to 5 years to life.

Science of PAI

Personal profile

PAI works with popular wearable devices to customize to your profile factoring in sex, age, and resting/maximum heart rate.

PAI Score

The proprietary algorithm calculates a PAI Score using personal profile data and heart rate data on a rolling 7-day basis.


Maintaining a weekly PAI Score of 100 or more is associated with an average 25% risk reduction in cardiovascular disease mortality.

What moves you?

Improving your cardiorespiratory fitness isn’t just through traditional step-based activities like running — you can bike, swim, dance; do anything that gets your heart rate up.

Check out the ‘Earn More PAI’ section of the app to learn what other activities you can do to earn PAI and improve your CRF.

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