| Although numerous studies have shown an association between operation of heavy construction equipment and symptoms of musculoskeletal disorders, very little research has been performed that characterizes the ergonomic exposures of operating engineers. It is believed that reducing ergonomic exposures, such as whole body vibration and postural stress, may be an important factor in improving the health, comfort and efficiency of these operators. The objectives of this study were to evaluate: (1) vibration at the seat/operator interface in three orthogonal axes; (2) transmissibility of vibration in the vertical axis; (3) psychophysical ratings of vibration level and vibration discomfort; and (4) postural requirements of the job. Vibration measurement and analyses were performed in accordance with the ISO 2631 standard. The psychophysical responses were collected using a visual analog scale. Posture was evaluated from videotape using the simulated real-time postural assessment system. The study was performed at several different construction sites in the Boston, Massachusetts area. Eight experienced journey-level operators employed by two major contractors participated in this study. The equipment evaluated for this study was categorized into three different sizes (small, medium, and large). The vibration levels and psychophysical responses were obtained both when the equipment was idling and performing dynamic tasks (e.g., digging). The postural requirements of the operator were evaluated only when the equipment was performing digging-related tasks. The results of this study indicate that the digging operation had higher levels of total weighted acceleration than high or low idling. The transmissibility data showed that the seat was amplifying vibration in the lower frequencies. Therefore the seats in the equipment may not be sufficient in protecting operators from long-term effects of vibration exposure. There was good correlation among the subjective ratings (vibration discomfort and vibration level), but weaker correlation between subjective ratings and quantitative vibration levels. The operator's subjective evaluation of discomfort from whole-body vibration appears to be a useful tool for quantifying the perceptions experienced by these operators. The postural evaluations revealed that the operators were required to assume awkward postures of the trunk, shoulders, and neck while performing their jobs. |
