Assessing Trailer Material Handling Tasks: Biomechanical Modeling, Posture Categorization, Physiological Measure, and Subjective Rating

Many variations of conveyor, facility, and trailer designs are available to aid the human operator in manual materials handling (MMH). This thesis describes an investigation to determine which of four different designs used in trailer MMH place the least physical stress on the human operator when unloading materials. Each trailer MMH design was evaluated by the criteria of biomechanical loading, working posture, physiological measure, and subjective rating of exertion. These four methods were used to generate four dependent measures: L5/S1 Compression Force, OWAS Action Category, mean heart rate, and Borg CR-10 RPE.

While no single assessment method provided a clear means for quantifying level differences in physical stress among MMH conditions, the methods employed furnished insight into which techniques and protocols might be useful in studying similar working situations. Based on relative sensitivity, ease of application, and administrative and equipment costs, the OWAS method was recommended as an assessment method useful for evaluating similar MMH work. The summary results of the four methods provided information to meet the experimental goals of this research and allowed conclusions to be drawn for the major areas of interest. Specifically, statistically significant differences were found between the Drop-frame - Floor Rollers condition and all other conditions in the SSPM - Placement analysis, between the Flat-floor - Power and the Drop-frame - Suspended Rollers conditions in the OWAS - Acquisition analysis, and between the Drop-frame - Suspended Rollers and the Drop-frame - Floor Rollers conditions in the OWAS - Placement analysis.