The Apple Watch has been found to have the most accurate heart rate sensor in a new research study conducted by Standford University and the Swedish School of Sport and Health Services. The heart rate tracking functionality of the Apple Watch was measured alongside six other fitness trackers including the Microsoft Band, PulseOn, Samsung Gear S2, Basis Peak, Fitbit Surf, and Mio Alpha 2.
60 participants took part in the study which comprised of 29 males and 31 females, with many of them wearing multiple fitness trackers. The data collected from all the wearables was compared to the data collected from an ECG machine and a clinical grade indirect calorimetry for the energy/calories burned.
Six of the devices achieved a median error below 5% for HR on the cycle ergometer task; the Samsung Gear S2 achieved a median error rate of 5.1% (2.3%–7.9%). For the walking task, three of the devices achieved a median error rate below 5%: the Apple Watch, 2.5% (1.1%–3.9%); the PulseOn, 4.9% (1.4%–8.6%); and the Microsoft Band, 5.6% (4.9%–6.3%). The remaining four devices had median error between 6.5% and 8.8%. Across devices and modes of activities, the Apple Watch achieved the lowest error in HR, 2.0% (1.2%–2.8%), while the Samsung Gear S2 had the highest HR error, 6.8% (4.6%–9.0%).
In the research, the Apple Watch had the lowest overall error in both heart rate measurement and energy expenditure, with the Gear S2 doing the worst. A median error of only 2 percent is well within the margin of error and makes the HR readings from the Apple Watch highly accurate and good enough for use in medical purposes.
Overall though, the research notes that while most wearables are able to track heart rate with a 5 percent error of margin in laboratory-based activities like walking, running, and cycling, they fail to properly estimate the calories burnt. The media error rates across all wearables varied from anywhere between 27.4 percent to 92.6 percent, which makes the data from them highly inaccurate. The Apple Watch did post the best results, but again, its data was wildly inaccurate.
So, while the heart rate data collected from them can be used for clinical purposes, the energy expenditure data should not be trusted.