Stanford study hails the Apple Watch’s heart rate monitoring function, points out shortcomings in calorie counting feature

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Date: Thursday, May 25th, 2017, 05:34
Category: Apple Watch, Hardware, News, Wearables

The good news is that the current Apple Watch features one of the most accurate heart rate monitors on the market.

The bad news is that its calorie counting feature could use some work.

A new medical study from Stanford University published in the Journal of Personalized Medicine on Wednesday sought to determine the validity of readings from commonly worn fitness trackers. The growing number of consumers buying and wearing devices with biometric capabilities presents a unique opportunity for preventative cardiovascular medicine, but error rates of these commercial products are largely unknown, the study says.

“People are basing life decisions on the data provided by these devices,” Euan Ashley, DPhil, FRCP, professor of cardiovascular medicine, of genetics and of biomedical data science at Stanford said in a statement. Ashley also stated that consumer devices are not bound by the same regulations as medical-grade equipment, making it difficult for doctors to quantify or otherwise apply generated data to diagnoses.


The study reviewed the limitations of the Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, MIO Alpha 2, PulseOn and Samsung Gear S2 against FDA approved equipment.

Within the study, a group of 60 volunteers – 31 women and 29 men – each tested up to four consumer devices and participated in 80 physical tests ranging from cycling to running. Test subjects were simultaneously monitored by a 12-lead electrocardiogram and continuous clinical grade indirect calorimetry, the latter measuring for expired gas.

Researchers conducting the study set an acceptable error rate of 5 percent. Within the study, the Apple Watch was able to achieve the highest heart rate accuracy, demonstrating an error rate of 2 percent while the Basis Peak and Fitbit Surge followed behind. Samsung’s Gear S2 exhibited the highest HR error rate at 6.8 percent, outside of the study’s acceptable limits.

All seven devices tested poorly in energy expenditure, or calorie counting, tests. The Fitbit Surge proved the most accurate, but demonstrated an error rate of 27.4 percent while the PulseOn clocked in at an error rate of 92.6 percent.

The research team has not offered an explanation as to why the energy expenditure/calorie counting feature was so far from the accepted gold standard for medical devices, albeit the study noted that each device uses its own proprietary algorithm for calculating calorie burn. These calculations are in large part based on individual user metrics like height, weight, BMI, fitness level, age and more. Whereas heart rate is measured directly from a user’s wrist, calorie burn is an estimate derived through complex algorithms.

The team is currently working on an extension of the study that applies its results to real world functions.

Stay tuned for additional details as they become available.

Via AppleInsider and the Journal of Personalized Medicine

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