Intermonitor Variability of Garmin Vivofit® Jr. Wristband

The main objective of this study was to evaluate the reliability of Garmin Vivofit® Jr. physical activity (PA) wristbands during daily life physical activities. Six wristbands were randomly selected from a stock of twenty-four. The wristbands were worn by a single four-year-old participant, with three on the right wrist area and three on the left wrist area. To assess device reliability under laboratory conditions on a treadmill (Powerjog, model JM200, Sport Engineering Ltd., Birmingham, UK), the participant wore the six wristbands while performing five work conditions: sitting and standing (30 times per minute, controlled by a metronome), walking at 3 km/h, walking at 4 km/h, running at 5 km/h, and running at 6 km/h. Throughout the six minutes, variables related to physical activity provided by the device, step volume, and minutes of physical activity were recorded using the specific application of the wristband (Garmin International Inc., Olathe, KS, USA). The intraclass correlation coefficients (ICCs) were high for all six wristbands with each other, for both the number of steps taken (ICC = 0.991–0.998) and the number of minutes of PA (ICC = 0.892–0.977). The critical alpha value of the Cusum test was highest at.050 for all wristband associations. In conclusion, good reliability was found among the six wristbands, which could be adopted for field-based research to quantify physical activities.