The Validity and Reliability of the Mi Band Wearable Device for Measuring Steps and Heart Rate.

The study objectives were to 1) evaluate the criterion validity and reliability of the Mi Band 2 wearable activity monitor to measure steps during a six-minute walk test (6MWT), a treadmill walking test at various speed (1.28 km/h, 1.92 km/h, and 2.88 km/h) and a stair climbing test; 2) assess the validity and reliability of the monitor to measure heart rate during rest and exercise. Fourteen participants (females: n = 8; mean age ± SD: 23 ± 4.2) completed the study. The mean body mass index was 22 ± 3.6. The majority (~92%) of the Mi Band met the standard of 5% absolute percent error for measuring steps during the 6MWT. However, the Mi Band underestimated steps at slower walking speeds (< 2.88 km/h). Mi Band showed good internal consistency during the six-minute walk test and stairs climb (ICC: 0.83). The validity and reliability of the Mi Band to measure heart rate may not be suited for clinical or research use. The Mi Band significantly underestimated heart rate during exercise. Overall, caution is required when interpreting the steps recorded (at slower speeds) and heart rate measurements.