Methods for objective measure, quantification and analysis of sedentary behaviour and inactivity

The purpose of this study was to develop and test a generic technique to robustly quantify the pattern of sedentary behaviour from objective records. The technique was applied to four groups of subjects: a healthy group with an active occupation (N = 54), a healthy group with a sedentary occupation (N = 53), a group of subjects with chronic low back pain (N = 5) and a group of subjects with chronic fatigue syndrome (N = 14). This study presents the first evidence that bouts of sedentary activity are power law distributed. Results showed that there was no significant difference in total sedentary time between the groups, however, the patterns of accumulation of sedentary time were significantly different for the groups. Sedentary groups accumulated their total sedentary time from a small number of longer sedentary bouts. Active groups tended to break their sedentary time into a greater number of shorter bouts. This suggests that the power law exponent a and the GINI index G, used to describe the pattern of accumulation of sedentary time, could be used to evaluate and quantify sedentary behaviour. (C) 2009 Elsevier B. V. All rights reserved.