False step? Why you can’t count on data from some smartwatches, fitness trackers

Consumers should not rely on smartwatches to track their fitness levels for medical purposes, a Hong Kong watchdog has warned, after a test showed the data could deviate by as much as 74 per cent.

The Consumer Council revealed on Thursday that three models out of 44 tested smartwatches and fitness trackers that were locally available had deviations of between 59 per cent and 74 per cent when counting steps taken by the user, which could be caused by including minor hand movements.

Heart-rate measurements also varied, with two models showing deviations of more than 11 per cent for most activities and as much as 21 per cent during cycling.

“The health and fitness data collected by smartwatches or fitness trackers is for estimation only and not necessarily accurate. Thus, they are suitable only for reference and not for medical use,” said Chung Chi-yung, chairman of the council’s research and testing committee.

The test, which was conducted by a European laboratory, included 38 smartwatch models that cost between HK$199 and HK$9,799 (US$25 and US$1,255) and six fitness trackers priced from HK$139 to HK$498.

Three assessors wore a sample of each model during various activities, including resting, low-intensity walking, high-intensity running and cycling. The recorded data was then compared with figures obtained from precision instruments used at the same time.