The Accuracy of Wrist-Worn Activity Monitors at Measuring Energy Expenditure During Different Forms of Physical Activity

The accuracy of activity monitors are critical to the proper functioning of artificial pancreas (AP) systems. The objective of this thesis was to assess the accuracy of activity monitors at measuring energy expenditure (EE) during physical activity. In two separate studies, the Fitbit Charge 2 (FC2), Garmin vvosmart HR+ (GVHR+), Fitbit Ionic (FI), and Garmin vvosmart 3 (GV3) were assessed during 4-5 types of physical activity in 15-20 adults. In Study A, the GVHR+ displayed significantly less negative bias in EE than the FC2 (FC2: -19.3 28.9%, GVHR+: -1.6 30.6%, P<0.001). In Study B, the GV3 displayed less positive bias in EE than the FI (FI: 15.7 36.0%, GV3: 7.0 36.3%). The GV3 significantly overestimated EE in T1D subjects compared to healthy controls. None of the activity monitors tested are ready to be incorporated into an AP system, but the GV3 is approaching the accuracy required.