The Sedentary Sphere is a method for the analysis, identification, and visual presentation of sedentary behaviors from a wrist-worn triaxial accelerometer.
This study aimed to introduce the concept of the Sedentary Sphere and to determine the accuracy of posture classification from wrist accelerometer data.
Three samples were used: 1) free living (n = 13, ages 20–60 yr); 2) laboratory based (n = 25, ages 30–65 yr); and 3) hospital inpatients (n = 10, ages 60–90 yr). All participants wore a GENEActiv on their wrist and activPAL on their thigh. The free-living sample wore an additional GENEActiv on the thigh and completed the Multimedia Activity Recall for Children and Adults. The laboratory-based sample wore the monitors while seated at a desk for 7 h, punctuated by 2 min of walking every 20 min. The free-living and inpatient samples wore the monitors for 24 h. Posture was classified from wrist-worn accelerometry using the Sedentary Sphere concept.
Sitting time did not differ between the wrist GENEActiv and the activPAL in the free-living sample and was correlated in the three samples combined (rho = 0.9, P < 0.001), free-living and inpatient samples (r ≃ 0.8, P < 0.01). Mean intraindividual agreement was 85% ± 7%. In the laboratory-based and inpatient samples, sitting time was underestimated by the wrist GENEActiv by 30 min and 2 h relative to the activPAL, respectively (P < 0.05). Posture classification disagreed during reading while standing, cooking while standing, and brief periods during driving. Posture allocation validity was excellent when the GENEActiv was worn on the thigh, evidenced by the near-perfect agreement with the activPAL (96% ± 3%).
The Sedentary Sphere enables determination of the most likely posture from the wrist-worn GENEActiv. Visualizing behaviors on the sphere displays the pattern of wrist movement and positions within that behavior.
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1Health and Use of Time Group, Sansom Institute for Health Research, University of South Australia, Adelaide, AUSTRALIA; 2Exercise for Health and Human Performance Group, Sansom Institute for Health Research, University of South Australia, Adelaide, AUSTRALIA; 3Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, UNITED KINGDOM; 4GENEActiv, ActivInsights, Cambridgeshire, UNITED KINGDOM; 5Centre for Research on Exercise, Physical Activity and Health, School of Human Movement Studies, University of Queensland, Brisbane, AUSTRALIA; and 6International Centre for Allied Health Evidence, Sansom Institute for Health Research, University of South Australia, Adelaide, AUSTRALIA
Address for correspondence: Alex V. Rowlands, Ph.D., Senior Research Fellow School of Health Sciences, University of South Australia, GPO Box 2471 Adelaide, SA 5001, Australia; E-mail: Alex.Rowlands@unisa.edu.au.
Submitted for publication August 2013.
Accepted for publication November 2013.
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