Objective measurement of sedentary behaviour using accelerometers: A survey of University of Otago employees working in sedentary occupations

Background: Prolonged sitting is associated with poorer cardio-metabolic health. Furthermore, repeated and regularly performed short bouts of activity interrupting prolonged sitting reportedly have a positive effect on cardio-metabolic health. Employment in an office-based occupation commonly involves prolonged sitting, therefore, regular activity breaks in office workers may be beneficial. To help design intervention studies aimed at encouraging regular activity breaks, detailed information on office workers’ existing patterns of sedentary behaviour and physical activity is required. Objective: To describe the amount and patterns of sedentary behaviour and physical activity of University of Otago employees who self-identify as having sedentary occupations. Methods: University of Otago employees (n = 78; mean age 45 years; body mass index 26.4 (5.2) kg/m2; 23% male) who self-identified as being employed in sedentary occupations were recruited. Participants were required to wear both the ActiGraph GT3X+ and the activPAL3 accelerometers during waking hours for seven consecutive days. Absolute and percentage time spent in sedentary behaviour, light-intensity physical activity and moderate-to-vigorous physical activity were summarised using the ActiGraph. Absolute and percentage time spent sitting/lying, standing and stepping, and number of sit-to-stand transitions were summarised using the activPAL. The mean number of breaks in sedentary time, prolonged sedentary bouts of at least 30 minutes and steps were calculated using both devices. Sedentary outcome measures were compared between workdays and non-workdays, work hours and non-work hours and between occupation categories. Results: The ActiGraph revealed participants spent between 65% and 79% of their work hours sedentary – using the vector magnitude and y-axis respectively, 16% of time participating in light-intensity physical activity and 4% of time participating in moderate-to-vigorous physical activity. The activPAL revealed participants spent 76% of their work hours in a sitting/lying position, 16% standing and 8% stepping. On average, participants accumulated 18 to 29 total breaks in sedentary time per day during hours of work using both devices. Defining a break as having to be preceded by at least five minutes of sedentary time reduced the number of breaks identified to 10 to 12 per day during hours of work. Administration staff accumulated an additional 6 to 7 breaks in sedentary time per day than other occupation categories (P < 0.001). Participants accumulated 13% to 16% more sedentary time during work-hours compared to non-work hours on a workday, and 7% to 9% more sedentary time on workdays compared to non-workdays (P < 0.001). The average number of breaks in sedentary time was higher during work hours compared to non-work hours and on workdays compared to non-work days (P < 0.001). Conclusion: The findings of this study confirm that office workers spend a high proportion of their work hours sedentary, however, this sedentary time is frequently interrupted with breaks, especially for those in administration roles