New study shows the limitations of fitness and health tracking devices

Smartwatches and fitness trackers adorn more wrists than ever before, and the majority of users are as interested in their health and fitness stats as their smart tools. Here at Android Authority, we consistently give equal weight to a device’s capabilities and accuracy when reviewing a new watch or band. However, it’s important to remember that wearables are intended to guide users, not provide pinpoint accuracy or medical-level feedback. A recently published umbrella review underscores the limitations of health and fitness tracking stats and reminds users to consider their stats with a grain of salt.

Starting with the positives, the review found that most wearable devices can measure your heart rate within 3% accuracy and can record equally reliable heart rate variability as well as potential signs of arrhythmia. Wearables can also provide solid estimates related to cardiorespiratory fitness, typically referred to as VO2 max on your device. These metrics are central to a broad range of health and fitness monitoring, and heart rate sensor accuracy is often a focus of new launches.

On the flip side, the review found far less accuracy regarding calorie data. We’ve discussed the hurdles of this metric in the past, but while it’s no surprise to see these findings, roughly 15 to 21% inaccuracy is worth noting. Calorie burn is a metric most often used by those closely managing their weight, and incorrect data used without skepticism can have negative consequences.

Likewise, the study also found sleep time and sleep efficiency inaccurate by more than 10% and sleep latency as high as 180% inaccurate when comparing wearables to polysomnography. Sleep tracking platforms have been expanding across the wearables field, but most reviewers consistently voice disclaimers about how closely these stats should be relied upon. Again, the best practice is to use your wearable for general guidance when trying to build better sleep habits, not as exact, concrete data.

In short, wearables are imperfect tools. While companies continue to refine and improve their capabilities, many provide health and fitness details that are not medically validated. When used with caution, however, smartwatches and fitness trackers are fantastic health companions. The most important thing shoppers can do is choose quality devices at checkout to reduce the unavoidable margin of error.