Meeting Physical Activity Guidelines Does Not Result In Less Sedentary Time

Background: Physical activity (PA) has long been associated with reduced all-cause and cardiovascular disease (CVD) mortality. More recently, time spent in sedentary behaviours has emerged as an independent risk factor for all-cause and CVD mortality. It is not well known if meeting PA guidelines reduces the amount of time spent in sedentary behaviours.

Purpose: To determine if meeting PA guidelines is associated with less time spent daily in sedentary behaviours.

Methods: Subjects (n=84; age 45.5±20.5 yr, BMI 24.9±4.5 kg/m2) wore an initialised (60Hz) ActiGraph GT3X+ accelerometer, positioned at their right hip, for a minimum of 4 days with 10 hours valid wear-time per day. Raw accelerometry data were processed in ActiLife v6.8.0 using a 60s epoch. Cutpoints developed by Freedson et al. (1998) were used with uniaxial accelerometer data for the determination of sedentary time (9642 cpm]). MVPA was determined by summing the daily minutes in moderate, vigorous, and very vigorous over one week. Relative time spent in sedentary behaviour was calculated as a percentage of the total valid wear-time. Subjects were classified as active or inactive based on the criteria of accumulating >150 minutes/week of MVPA, or >75 minutes/week of vigorous PA, in >10 minute bouts. Relative (%) and absolute (minutes) sedentary time were compared between PA classifications (active or inactive) using independent samples t-tests, with significance set at p<0.05.

Results: There were no significant differences between active and inactive subjects for relative (64% vs. 63%, p>0.05) or absolute (517±77 vs. 527±99 minutes, p>0.05) time spent in sedentary behaviours.

Conclusions: The results indicate that active and inactive subjects spent a similar length of time in sedentary behaviours. Studies looking at the prevalence of the population meeting PA guidelines should consider sedentary behaviour analysis in order to give a broader context to the understanding of activity-related risk factors among the general population.