Zero Cadence as a Proxy Indicator of Sitting Behaviors in Objective Monitoring

Abstract

Consistent evidence has been presented regarding the potentially deleterious health consequences of prolonged sitting time independent of physical activity level. Zero cadence (0 steps/min) determined using accelerometers may be a suitable proxy measure of sitting behaviors since theoretically no steps should be registered in this position. PURPOSE: The purpose of the current study was to determine the capability of accelerometer-determined zero cadence to predict seated activities of daily living. METHODS: A total of 80 young adults (mean age 29.8±6.7 years), 10 men and 10 women representing each 5-year age-group category between 21-40 years (21-25, 26-30, 31-35, 36-40) performed lab-based simulated daily living activities (i.e., seated rest, watching a movie, computer work, folding laundry while standing, vacuuming, stair stepping and a self-paced over-ground walk) while concurrently wearing multiple (n=7) research-grade (e.g., ActiGraph, ActivPAL, ActiCal and StepWatch) and consumer-grade (e.g., Fitbit One and Vivofit2) accelerometers on manufacturer-indicated locations (i.e., hip, wrist, thigh or ankle). Receiver Operating Characteristic (ROC) analyses were conducted to examine the accuracy of zero cadence for classifying sitting behaviors (e.g., seated rest, watching a movie and computer work) among the performed activities. Sensitivity, specificity, accuracy and area under the ROC curve (AUC) values were compared for each device. RESULTS: All devices demonstrated the capability of using zero cadence to determine sitting activities with high combined sensitivity and specificity (e.g., ranges between 75-98%). AUC values of all devices were above 0.8 (p<.001) indicating good or excellent discrimination ability of zero cadence. Vivofit2 and wrist-worn ActiGraph provided the highest (93%) and lowest (75%) accuracy, respectively. CONCLUSION: In agreement with zero cadence, both research- and consumer-grade activity monitors provided valid capacity for discriminating seated activities from common daily living activities. Based on this preliminary analysis it appears that accumulated time spent at zero cadence obtained by activity monitors can be used as a proxy indicator of time spent sitting. Supported by NIH/NIA Grant 5R01AG049024-03 – CADENCE-Adults study