Accuracy of Xiaomi Mi Band 2.0, 3.0 and 4.0 to measure step count and distance for physical activity and healthcare in adults over 65 years.

Background: The measurement of step count and distance covered are of interest in healthcare and rehabilitation medicine, so fitness trackers and smartwatches have incorporated these metrics. In 2014, the introduction of new brands of these devices peaked, although the highest number of new devices was introduced in 2015. Even though Mi Band Xiaomi was among the top 5 regarding sales, it is not at the top of the fitness bands considered in research articles.
Research Question: this study aimed to assess the validity of Xiaomi Mi Band 2.0, 3.0 and 4.0 for recording steps and distance covered.
Method: The data were recorded from 26 elderly adults (71.2 ± 3.2 years old; 169.3 ± 5.8 height; 72.1 ± 9.2 weight), who covered the maximum distance possible at walking speed in a delimited outdoor space following different trajectories to compare data with the criterion measure, using three wristband devices (Xiaomi Mi Band versions 2.0, 3.0. and 4.0.).
Results: In step count, the average bias was small (<2.6 steps) and no statistical differences were found between instruments (p > 0.76; t=0.30). However, Xiaomi Mi Band 4.0 obtained questionable validity (ICC = 0.76) for distance estimation.
Significance: The accuracy of Mi Band Xiaomi 2.0., 3.0. and 4.0. may be considered as good to count the number of steps for physical activity monitoring, whereas distance estimation is considered questionable.
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