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 to 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-second epoch for the hip, and ≤105 counts per 15-second 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 (ICCs) were investigated.
Results
The hip and wrist accelerometer cut points and hip inclinometer function overestimated the number of hourly sit-to-stand transitions by approximately triple as compared to direct observation. ICCs between the ActiGraph methods and direct observation were all <0.12. Sit-to-stand transitions assessed from ActivPAL were within 17% of direct observation; ICC was 0.26.
Conclusion
Despite the common use of the 100 count hip-worn accelerometer cut point for assessing sedentary time, these processing decisions should be used with caution for assessing sit-to-stand transitions. Future research should investigate other processing methods for ActiGraph data, and studies investigating postural changes should consider including devices such as activPALs.
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