Postural Strategies of Bus Drivers During a Regular Work Shift in Urban Area: A Pilot Study

Bus drivers are forced to adopt constrained postures for a long time on a daily basis. This may cause discomfort and, in the long term, represent a co-factor for the onset of musculoskeletal disorders (MSDs), particularly in the low back. Objective measurements of biomechanical variables associated to sitting posture may be useful to better estimate the risk of MSD and, in this context, in recent times in chair movements (ICM) have been shown to represent a reliable tool to characterize sitting postural strategies. This study aimed to evaluate postural strategies of bus drivers during actual long-term driving session in urban area, through the analysis of ICM trend with shift time. Seven professional drivers were tested during regular 6- hours work-shift divided in 50 min point-to-point routes, interspersed by 10 minutes breaks at each last stop. Body-seat interface pressures were collected using a pressure sensitive mat and subjective discomfort rating was evaluated using a 2-parts questionnaire. The results show that, during the whole shift, most drivers report a constant increase in perceived discomfort and a correspondent increase in the overall number of ICM. However, it was interesting to observe that considering a single point-to-point route (i.e. the maximum amount of time in which the drivers must remain seated continuously) the number of ICM increase at the beginning of the period but then decrease significantly, probably when the optimal position to minimize discomfort is reached.