Peer-reviewed study puts Apple Watch fitness tracking to the test: Here's the takeaway

Phone Arena

a day ago

A peer-reviewed meta-analysis published recently provides potential answers for Apple Watch users who have questioned the accuracy of their Activity Ring data. The researchers at the University of Mississippi examined 56 studies which measured Apple Watch performance against medical-grade devices and obtained both positive and warning signals.
Apple Watches tend to have some of the best heart rate tracking among wearables. | Image by PhoneArena Let's start with the good news first. According to the findings, Apple Watches are highly accurate when it comes to tracking heart rate and counting steps. This is in line with our own experience with Apple Watches, including during our Apple Watch Series 10 review (Apple's latest smartwatch).
The mean absolute percent error (MAPE) for these metrics in the meta-analysis was just 4.43% for heart rate and 8.17% for step count — both well below the 10% threshold typically used to define excellent performance in consumer wearables.
The researchers also noted that newer Apple Watch models performed better across the board. While the study doesn't specify model-by-model results, doctoral student Ju-Pil Choe (one of the study authors) says:
Smartwatches are still not that great at tracking calories, but that doesn't mean you can't use them for motivation. | Image by PhoneArena But not all metrics scored so well. The study found that estimates of energy expenditure — aka how many calories you burn — were far less reliable. The average error rate here jumped to 27.96%, with inaccuracies present across various activities, including walking, running, cycling, and high-intensity workouts.
That puts Apple Watch roughly on par with other wearables, like the Fitbit Surge, which also struggles with calorie estimates. This shouldn't come as a surprise, though, as it is an extremely difficult task to measure calories burned. There are all kinds of things to factor in like body weight, movement type, metabolic efficiency, and even skin tone. Smartwatches often rely on general algorithms that combine heart rate data, sensor input, and user profile info to estimate calorie burn. But that process leaves plenty of room for error. Other studies have found that calorie estimates on wearables can be off by as much as 40% to 80%, depending on the device and activity.
Use the Apple Watch — or any smartwatch, for that matter — as a guide, not gospel. The University of Mississippi study provides a helpful reality check: Apple Watches are excellent at tracking heart rate and step count but should not be relied on for precise calorie measurements. Personally, I find a smartwatch most valuable as a way to log workouts and monitor consistency. There's something genuinely motivating about seeing your progress visualized, whether it's a graph of completed runs or a streak of active days.That said, I've also left my watch behind on occasion, and there's a certain freedom in it. Without the pressure of stats or metrics, you start to tune into how your body feels in the moment — and sometimes, that's exactly the kind of workout you need.