PAI stands for Personal Activity Intelligence, a fitness metric built into Amazfit and Zepp smartwatches that converts your heart rate data into a single score. Instead of tracking steps or calories, PAI measures how hard your heart is actually working throughout the day and week, giving you one number to aim for: 100.
How PAI Works
PAI is based on continuous heart rate monitoring. Your watch tracks your heart rate throughout the day, and any time it rises above your resting level, you start earning PAI points. The harder your heart works, the faster you accumulate points. A brisk walk earns points slowly, while a run or cycling session at higher intensity earns them much faster.
The algorithm was developed by researchers at the Norwegian University of Science and Technology (NTNU) and is personalized to you. It factors in your age, sex, resting heart rate, and maximum heart rate, so two people doing the same workout won’t necessarily earn the same score. Someone who is less fit will earn points more quickly from moderate effort, while a highly trained athlete needs to push harder to accumulate the same amount. This makes PAI a more individualized measure than step counts, which treat every person the same regardless of fitness level.
The Rolling 7-Day Window
Your PAI score isn’t a lifetime total. It operates on a rolling seven-day window, meaning points you earned eight days ago drop off your score. This design rewards consistency over single big efforts. You can’t bank a massive workout on Monday and coast through the rest of the week without watching your score decline.
The practical effect is that your PAI score rises when you’ve been active recently and falls during inactive stretches. If you take several days off, you’ll see the number drop as older points expire. This keeps the metric forward-looking and always reflects your current activity level.
Why 100 Is the Target
The magic number is 100 PAI per week. This target comes directly from a large-scale study called the HUNT Study, which tracked tens of thousands of people in Norway over decades. Participants who consistently maintained a PAI score of 100 or higher had a 36% lower risk of dying from cardiovascular disease and a 24% lower risk of dying from any cause, compared to inactive individuals. These benefits held regardless of whether people met traditional exercise guidelines based on minutes per week.
You don’t need to hit 100 every single day. The goal is to keep your rolling seven-day total at or above 100. Some days you might earn 30 or 40 points from a tough workout, other days just a handful from normal daily movement. As long as the weekly total stays around 100, you’re in the health benefit zone. Going above 100 doesn’t appear to provide significantly greater protection, so there’s no pressure to chase extremely high scores.
How to Earn Points Faster
Intensity is the key driver. Activities that push your heart rate into higher zones earn PAI points at an accelerating rate. A 20-minute high-intensity interval session can earn as many points as an hour of moderate walking. This doesn’t mean you need to do intense exercise every day, but mixing in a couple of vigorous sessions per week makes it much easier to maintain 100 PAI without spending hours exercising.
Any activity counts as long as your heart rate rises. Swimming, dancing, playing with your kids, carrying heavy groceries upstairs. PAI doesn’t care what the activity is or whether you log it as a formal workout. It only cares about what your heart is doing.
Setting Up PAI on Your Amazfit Watch
For PAI to work accurately, your Amazfit watch needs to monitor your heart rate continuously or at frequent intervals. In the Zepp app (the companion app for Amazfit watches), make sure automatic heart rate detection is turned on and set to a frequent measurement interval, ideally every one to five minutes. If heart rate monitoring is set to manual only or at very long intervals, the watch won’t capture enough data to calculate a meaningful PAI score.
You can view your current PAI score directly on the watch face (many Amazfit watch faces display it) or in the Zepp app under your health data. The app also shows a breakdown of how your score has changed over the past seven days, so you can see which activities contributed the most and when older points are about to expire.
PAI vs. Steps and Calories
Step counting treats all movement equally and ignores intensity entirely. You could hit 10,000 steps by shuffling around a grocery store, which barely challenges your cardiovascular system. Calorie estimates on wearables are notoriously inaccurate and hard to interpret without context.
PAI simplifies things by tying your score directly to cardiovascular effort, which is the factor most strongly linked to long-term health outcomes. It also adjusts to your personal fitness, so it stays relevant whether you’re just starting to exercise or training for a marathon. For people who find it tedious to track multiple metrics, PAI offers a single number with a clear, research-backed target.