The effects of posture, whole body vibration, and personal factors on reported discomfort levels of operators during a simulated underground haulage vehicle ride

The purpose of this study was to examine the effects of posture on the reported discomfort levels of operators of simulated underground haulage trucks with the goal of developing and testing a discomfort questionnaire that can be used in the field. Thirty male subjects between the ages of 19 and 30 years, with no prior history of back or neck disorders, volunteered to participate in the study. For a 1-hour period, subjects drove a driving simulator that mimicked the vibration characteristics of an underground haulage truck. During that period, subjects rated their perceived discomfort levels every 15 minutes using a Body Map and the 50-Point Category Partitioning Scale. Body posture of the subjects' left side was also measured by developing a 14-point link segment model of the subjects from videotaped data of the simulation. Information was also collected on the subjects' previous musculoskeletal history, anthropometric measurements, perceived fitness levels, and their exposure to whole body vibrations. Major findings of the study indicated (a) that there was a positive linear relationship between reported discomfort and the duration of driving; (b) that postures that deviated from a neutral position resulted in more reported discomfort; and (c) that during the simulation, with the exception of the left elbow and knee angle, the postures of the operators remained relatively static. It was also found that factors such as the positioning of the backrest, previous musculoskeletal problems, anthropometric measurements of the subjects, perceived fitness levels of the operators, and exposures to whole body vibration, all played a factor in reports of discomfort. Further, due to the relationship found between the reported discomfort of the subjects and their posture, the discomfort questionnaire used in the study is appropriate for field-testing.