Assessing Posture And Activity Intensity Agreement Between Wearable Camera Images And Criterion Direct Observation

PURPOSE: To compare posture and activity intensity estimates annotated from wearable camera images (WCI) to criterion video-recorded direct observation (DO). METHODS: 19 healthy adults were observed over 53 visits (mean visit length = 89.7 ± 19.2 minutes), in a location of their choice. During these visits, participants were video-recorded performing free-living activities of daily living, while wearing a wearable camera at chest level. The camera was set to a high capture rate, where it took first-person images. Researchers annotated the WCI and DO videos for posture (sitting, standing, and movement). Activity intensity (sedentary, light, moderate-vigorous) from DO videos was determined from posture, while WCI were coded using a schema with matching Taylor codes to the Compendium of Physical Activities to extrapolate activity intensity. For analysis, a linear mixed-effects model calculated statistical bias and 95% CIs of WCI posture and activity intensity time in minutes to DO. Cohen’s weighted Kappa statistic (Κ) was calculated to assess the agreement of posture and activity intensity annotations to criterion DO. RESULTS: 4754 minutes of WC and DO data were collected. Significant bias was calculated for all outcome measures except movement posture (Figure 1). Kappa showed substantial agreement between WCI and DO to assess posture (K = 0.76), and moderate agreement between WCI and DO for estimating intensity (K = 0.55). CONCLUSIONS: When assessing posture in healthy adults, WCI show substantial agreement with criterion DO. WCI show moderate agreement with DO when used to estimate activity intensity. Future studies should explore WCI’s estimates of posture and activity intensity in more diverse populations and validate WCI activity intensity estimations against gold standard measurements of energy expenditure.