How accurately does that smartwatch or fitness tracker you’re wearing measure your heart rate? Modern wearables are more popular now than ever, but, are they reliable? How does that device on your wrist measure the ebbs and flows of your heartbeat? “By standard convention, your heart rate is reported by how many times it beats per minute. How fast your heart beats depends on many factors, like your age, your level of fitness and your activities,” says Dr. Christopher Madias, Director of the Cardiac Arrhythmia Center at Tufts Medical Center. Most commonly, smartwatches and other wearables use optical heart rate sensors to measure heart rate, which detect the blood coursing through your veins, oftentimes via LED lights (using a technology called photoplethysmography).
According to Dr. Madias, this technology is proven to be quite accurate most of the time, but sometimes there can be variability in the accuracy of your reported heart rate.
“Another way some wearables measure your heart rate is by actual electrocardiograms (ECGs),” says Dr. Madias. “This allows the device to provide a more accurate heart rate and sometimes an interpretation of your heart rhythm, and these types of devices can actually be very useful in tracking symptoms associated with arrhythmias including a very common arrhythmia called atrial fibrillation.”
In addition to measuring your steps, tracking your sleep and sending reminders to get moving and stay active, becoming familiar with your heart rate’s spikes and falls can help you to analyze your performance. However, it’s important to understand the bigger picture of your overall heart health, rather than solely relying on the number on your wrist. A doctor is often the best person to guide you on these issues.
