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article imageFitness trackers underestimate calories

By Tim Sandle     May 25, 2017 in Health
A new assessment of fitness trackers reveals that the devices on the market are good at measuring heart rate but they are often poor at measuring calories burned.
The new study comes from Stanford University and it warns that users should be wary about using the devices to assess the number of calories they consume and in making decisions about they types of food to eat. The findings have come from tests on seven wrist devices using 60 volunteers.
The devices tested were:
Apple Watch, Fitbit Surge, Basis Peak, Microsoft Band, PulseOn and MIP Alpha 2, Samsung Gear S2
In terms of fitness, the research found six out of seven of the fitness devices were relatively accurate at estimating the heart rate of the person wearing it, with an error rate under 5 percent. However, the Samsung Gear S2 had an error rate outside of this range, recording an error rate of 6.8 percent.
What was of bigger concern was keeping track of energy used during exercise. Of the six devices, five had this functionality. Each device was found to be poor in terms of accuracy, with each device recording an error rate of above 20 percent. The most inaccurate device was PulseOn. The reason for the inaccuracy is due to the devices not assessing all of the necessary data, such as heart rate, height and weight. For example, 10,000 steps could equate to anything from 400 kilocalories to 800 kilocalories lost.
READ MORE: Fitness goal of many smart devices is 'meaningless'
Speaking with the BBC, lead researcher Dr Euan Ashley said: "People need to know that on energy expenditure they give rough estimates." This is because, the researcher exemplifies: "If you go to the gym, and you think you've lost 400 calories, then you might feel you've got 400 calories to play with."
Other findings of interest were:
The Apple Watch was the highest scoring in terms of heart rate and energy expenditure.#
The devices were better at measuring data collected during cycling than walking.
Errors also tended to be more common in men compared with women.
Errors were also worse for those with a greater body mass index and people with a darker skin tone.
READ MORE: Why your fitness wearable might be working against you
The study forms part of Stanford Medicine’s focus on precision health, the goal of which is to anticipate and prevent disease in the healthy and precisely diagnose and treat disease in the ill.
More about fitness apps, Fitbit, fitness tracker, Fitness, Exercise
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