Your PAI score is based on your age, sex, resting heart rate, and your past 7 days of heart rate data, so it’s personalized for your body. You earn PAI points by elevating your heart rate, so the more intense your workout (i.e. the higher your heart rate), the faster you'll earn PAI points. Anything that gets your body moving and your heart pumping counts (not just exercise and steps).
The higher your heart rate and the longer your heart rate is elevated, the more PAI you earn, allowing you to get healthy in less time by increasing the intensity.
Each morning any points accrued 7 days ago will expire, so you may see your score reduce on some days. You will need to earn PAI (i.e. exercise) regularly in order to maintain your PAI score. And if you know you can't exercise on some days, you can 'bank' your PAI points by exercising harder on the days that suit you so you can still reach 100 PAI points in a 7-day period.
As your PAI score increases, it will also become slightly more difficult to earn PAI points. You may notice that the exact same workout or run earns you half as many PAI points when you're starting from 0 PAI compared to starting from 100 PAI.
PAI is designed to strengthen your heart over time and adapts to your fitness level. As you get healthier and your resting heart rate decreases, PAI points become harder to earn. Just like if you started lifting weights, eventually you would increase the weight or number of repetitions to continue challenging yourself, similarly, PAI gets more difficult over time, too.
As you continue to earn PAI points, your score takes into account other factors such as past PAI scores, so it’s not as straightforward as simply adding your PAI score each day. While the exact formula is a secret, you can trust that the algorithm was created from analyzing 25 years of health data on 45,000 people. It has been scientifically validated and matches the American Heart Association's 2018 Physical Activity Guidelines.
PAI is meant to help improve your cardiorespiratory fitness (your heart’s health). Maintaining 100 PAI will reduce your risk of cardiovascular disease, but even reaching just 50 PAI still gives you 60% of the associated health benefits.
Also note that you can only earn a maximum of 75 PAI in a single day, so plan to exercise more than once a week to earn 100 PAI.