Understanding Adolescent Sedentary Behavior Using Accelerometry and Self-Report

Introductions: Physical inactivity is associated with a higher risk of obesity, type II diabetes, hypertension, stroke, psychological problems, and some cancers (1). Currently there are no recommendations in Ireland for sedentary behaviour (SB), however, Australian guidelines recommend <2hours a day in sedentary screen time (ST) behaviour (2).

Purpose: The purpose of this study was to identify the current levels of SB in a cohort of 11-13 year old adolescents.

Methods: s 266 participant’s wore Actigraph accelerometers for a period of 9days, and completed a self-report questionnaire to determine ST. Accelerometer data were included in analysis if they met the following inclusion criteria; >10hours wear time per day for a minimum of 3week days and 1weekend day. Data were then processed using the Evenson et al. (3) cut points. Data were subsequently filtered to give standardize average daily, weekday, weekend day, Before School (7:00-9:00), During School (9:00-16:00), After School (16:00-18:00), and Evening minutes (18:00-22:00) of SB.

Results: Accelerometer data showed participants spent on average 657.2minutes (10.95hours) per day in SB, with males accumulating significantly less time sedentary than females (p<0.001). Participants were significantly more sedentary on weekdays than on weekend days (p<0.001). Participants were significantly more sedentary in the During School period than the After School and Evening periods. Based on self-report data participants spent on average 1hour 54minutes per day on ST pursuits. A strong, positive correlation (r=.81, n=266, p<0.001) between levels of ST (self-report) and overall levels of SB (accelerometer) was found.

Discussion: This study illustrates youths are spending 10.95hours in SB per day, with 1hour 54minutes of this being spent on ST pursuits. As expected a positive relationship was identified between ST and time spent in SB. Although participants are not exceeding the sedentary guidelines (<2hours/day) the relationship between ST and time spent in SB would suggest that it may be fruitful to reduce ST in an attempt to reduce overall SB. The During School period provides opportunity for specific interventions and strategies aimed at encouraging physical activity participation. SB is difficult to classify adequately. In order to fully analyse and understand SB it is essential that a definition be developed, as well as global guidelines which consider total sedentary time in addition to ST guidelines.

References: 1. Centre for Disease Control and Prevention. Youth risk behavior surveillance. Rep. No. 49, United States. 2000. 2. Department of Health and Ageing. Get out and get active: Australia’s Physical Activity Recommendations for 12-18 Year Olds. 2004 3. Evenson, K. R., Catellier, D. J., Gill, K., Ondrak, K. S., & McMurray, R. G. Calibration of two objective measures of physical activity for children. Journal of Sports Sciences, 26, 1557-1565. 2008.

Contact danielle.powell4@mail.dcu.ie