Using Activity Monitors to Measure Sit-to-Stand Transitions in Overweight/Obese Youth

Introduction: Reducing sedentary behavior has emerged as an important health intervention strategy. Although hip-worn, and more recently wrist-worn, accelerometers are commonly used for measuring physical activity and sedentary behavior, they may not provide accurate measures of postural changes. The current study examined the validity of commonly used hip- and wrist-worn accelerometer cut points and the thigh-worn activPAL activity monitor for measuring sit-to-stand transitions as compared with direct observation in youth with overweight and obesity. Methods: Nine children wore three activity monitors while being directly observed. The monitors included a hip- and wrist-worn ActiGraph and thigh-worn activPAL. The hip-worn ActiGraph was processed with the normal- and low-frequency filters and the inclinometer function. Cut points of ≤25 counts per 15-s epoch for the hip and ≤105 counts per 15-s epoch for the wrist were applied to the vertical axis to identify sit-to-stand transitions. Epoch-level absolute agreement, Bland–Altman plots, mixed-effects linear regression, and intraclass correlation coefficients (ICC) were investigated. Results: The hip and wrist accelerometer cut points and the hip inclinometer function overestimated the number of hourly sit-to-stand transitions by approximately triple as compared with direct observation. ICC values between the ActiGraph methods and the direct observation were all

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