Accuracy and cross-validity of the Xiaomi Mi Band 2, 3, 4, and 5 wristbands in evaluating physical activity in adolescents according to WHO 2020 guidelines: School-Fit study.

Abstract

Background: The aims of the present study were to examine the accuracy and cross-validity of Xiaomi Mi Band (XMB) 2, 3, 4 and 5 activity wristband-measured daily physical activity thresholds related to achieving at least the recommended 60 minutes per day of moderate-to-vigorous intensity physical activity in adolescents.

Methods: Following a cross-sectional design, 70 adolescents (final sample=62; 54.84% females), aged 11-17 years old, from a public high school wore the activity wristbands XMB 2, 3, 4 and 5 (non-dominant wrist; index tests=steps, slow- and/or brisk-pace walking, total physical activity and moderate-to-vigorous physical activity) and ActiGraph wGT3X-BT accelerometers (right hip; reference standard=moderate-to-vigorous intensity physical activity) for a day. 29.03% of the adolescents achieved the moderate-to-vigorous intensity physical activity recommendation.

Results: The results of the Receiver Operating Characteristic curve analyses showed that the accuracy of the activity wristband-measured daily steps thresholds was excellent (e.g., Sensitivity=1.00, Specificity=0.91, k=0.85), being higher than those with intensity-related physical activity outputs. The cross-validity results showed that thresholds from 8,521 to 9,070 steps/day had excellent values (e.g., Sensitivity/Specificity ≥0.90, k≥0.75).

Conclusions: Activity wristband-measured daily steps thresholds are more accurate than those with intensity-related physical activity outputs for evaluating the recommended 60 minutes per day of moderate-to-vigorous intensity physical activity. A 9000-step-per-day recommendation is a simple and accurate activity wristband-based recommendation for adolescents.