The Feasibility of Reducing and Measuring Sedentary Time among Overweight, Non-Exercising Office Workers

Abstract

This study examined the feasibility of reducing free-living sedentary time (ST) and the convergent validity of various tools to measure ST. Twenty overweight/obese participants wore the activPAL (AP) (criterion measure) and ActiGraph (AG; 100 and 150 count/minute cut-points) for a 7-day baseline period. Next, they received a simple intervention targeting free-living ST reductions (7-day intervention period). ST was measured using two questionnaires following each period. ST significantly decreased from 67% of wear time (baseline period) to 62.7% of wear time (intervention period) according to AP (n = 14, P < 0.01). No other measurement tool detected a reduction in ST. The AG measures were more accurate (lower bias) and more precise (smaller confidence intervals) than the questionnaires. Participants reduced ST by ~5%, which is equivalent to a 48_min reduction over a 16-hour waking day. These data describe ST measurement properties from wearable monitors and self-report tools to inform sample-size estimates for future ST interventions.

Figures

Figure 1

Illustration of the under- and overestimation of sedentary time for each measure compared to the activPAL monitor for (a) weekend (b) weekdays. The closed circles are the bias and the lines illustrate the 95% confidence intervals. AG100 refers to the ActiGraph cut-point of 100 counts·min−1, AG150 refers to the ActiGraph cut-point of 150 counts·min−1, T-SQ is a single-item total sedentary time questionnaire, and D-SQ is a 5-domain sedentary time questionnaire. Data includes 13 participants with valid data for all measures during both the baseline and intervention period.