Characterization of the dynamics of sitting during a sustained and mentally demanding computer task

Abstract

This laboratory study studied the dynamics of sitting during a sustained and mentally demanding computer task. Mental fatigue ratings, overall performance and kinetic were recorded in 20 asymptomatic computer users performing computer work for 40 min divided in 12 time epochs. The displacement of the center of pressure (COP) in anterior-posterior (AP) and medial-lateral (ML) directions was calculated. The average, standard deviation, and sample entropy values were computed from the COP time series to assess respectively, the magnitude, size and complexity of sitting dynamics. Fatigue ratings significantly increased from before to after the computer task while the overall performance did not change significantly over time. Likewise, the direction of displacement of the COP did not affect significantly the AVG but resulted in larger SD and SaEn values in the ML direction compared with AP direction. Time did not play a significant role on any of the outcome measures. The present study demonstrated that the sitting dynamics can be assessed in an ecological environment, e.g. in office chairs. Further, we found that 40 min seated computer work did not changed the dynamics of sitting. On the contrary, we observed increased size and structure of variability in the ML than the AP direction. This latter finding can be used to design office chairs or interventions aiming at preventing discomfort due to long time sitting.