Fitness devices are unreliable at counting how many calories you burn during exercise, according to a report by The Guardian.
It stated that scientists working with Stanford University took seven consumer devices and measured their data against laboratory measurements, which revealed two distinct sets of results.
While fitness trackers performed “really quite well” when it came to measuring a wearer’s heart rate, the calorie estimates they produced were “poor”.
“They were really all over the map,” stated the researchers.
The seven devices which were tested were:
- Apple Watch
- Basis Peak
- Fitbit Surge
- Microsoft Band
- Mio Alpha 2
- Samsung Gear S2
31 women and 29 men each wore multiple devices at a time and were put on a treadmill and exercise bikes, and were also made to sit still.
The Apple Watch had the most accurate heart rate figures, with a median error rate of 2%.
“Errors on energy expenditure were far greater, ranging from the lowest at 27.4% for the Fitbit Surge to the highest error of 92.6% for the PulseOn device,” stated the report.