Significant Variation in the Accuracy of Smart Watch Fitness Data – Consumers Are Advised to Use the Data Only for Reference

15 January 2019
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Significant Variation in the Accuracy of Smart Watch Fitness Data –  Consumers Are Advised to Use the Data Only for Reference

Living a healthy lifestyle is crucial to stay fit, thus many consumer chose to wear smart watches and fitness bands to keep track of their daily activities and even calories burnt.  However, in a test of smart watches and fitness tracking bands in which the Consumer Council participated, the accuracy of their fitness data was shown to deviate widely compared with professional measuring instruments for example by over 60% in step counts and distance based on steps, and by a high of 88% in calories burnt.  Consumers are reminded that smart watches and fitness tracking bands are not precision measuring instruments.  Deviation between the data provided and the actual results is inevitable, so the data recorded should be used only for reference.

The so-called fitness data provided by smart watches and tracking bands are calculated based on user movement information gathered from the built-in sensors in the devices.  The fitness data estimated include step count, distance calories burnt and heart rate, as well as distance based on GPS, and even to measure height above sea level.

The test was coordinated by International Consumer Research and Testing (ICRT) on 20 models available in Hong Kong, comprising 17 smart watches, priced from $479 to $6,090, and 3 tracking band models, priced from $219 to $1,298.  Their overall performance rating was between 3 and 4.5 points.  The test focused on fitness data, smart functions, ease of use, apps, battery performance, and versatility.

The test compared the fitness data collected by smart watches and tracking bands with data collected by professional measuring instruments.  The results revealed that for counting walking steps, 9 samples were found to have significant deviations, ranging from 11% to 49%, and the most expensive sample was found to perform the worst.  In the test of the walking step count in daily life, 12 samples recorded a considerable deviation of 14% to 46%, though the models performed well in running step count accuracy, with only 1 model deviating 18%.

Regarding the accuracy in recording the calories burnt in walking, running, cycling and daily movement, none of the models tested was found to deviate by less than 10% in all estimates of calories burnt.  Of the 20 models, in the estimated number of calories burnt when cycling, 3 deviated as much as 87% and 88% respectively. Only 1 model deviated less than 10% in the estimated number of calories burnt when walking, and 2 deviated less than 10% for routine activities. 

The test also measured the deviation in estimated walking and running distance on specially selected winding routes and paths with no satellite signal for GPS.  1 model was found to deviate almost 42% in running distance, and another deviated up to 60% in walking distance.  Only 5 models were found to deviate less than 10% in both walking and running estimates.

Of the 13 samples that could measure altitude, 2 deviated over 35%, only 4 others did not exceed 5%.  Of the 13 samples that could measure distance based on GPS, the deviation in 1 sample was 55%.

Consumers should note that, GPS can usually operate more accurately in open spaces measuring distance, but factors such as winding routes and location tracking frequency of the device can result in wide data discrepancies.

Battery performance is also of concern to consumers.  The test showed a wide variation of twofold to fully recharge a battery, from 1.4 to 3.2 hours; and an even greater discrepancy of over tenfold in the battery life after the battery is fully charged, from 29 hours (over 1 day) to 294 hours (over 12 days).  The model with the shortest battery life, which lasted only 1 day, took 2 hours to recharge, which is worth noting particularly for frequent users of the device.

On the evaluation of versatility and other smart features, the performance was satisfactory on the whole. For instant messaging, all models were able to emit a clear vibration alert upon receipt of messages, but none could send out a valid alert regarding messages from Facebook as a social media. 

When shopping for smart watches and tracking bands, consumers should note that trendy devices with multiple smart features are not precision measuring instruments and that the fitness data provided by these devices are only estimations.  If they would like to get fitness data for health assessment, they should consult professional healthcare practitioners.


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