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. 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.
Each day any points earned 7 days ago will expire and your PAI Score will be recalculated. You will need to earn PAI regularly in order to maintain your PAI Score. 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 hit your goal in a 7-day period.
As your PAI Score increases, it will also become slightly more difficult to earn more PAI. You may notice that the exact same workout or run earns you half as many PAI when you're starting from 100 PAI compared to starting from 0 PAI.
PAI is designed to strengthen your heart over time and adapt to your evolving fitness level. As you get healthier and your resting heart rate decreases, PAI becomes 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.