Quantifying Localized Muscle Fatigue of the Forearm during Simulations of High Pressure Cleaning Lance Tasks
Localized muscle fatigue (LMF) has been proposed as a surrogate measure to injury, since the onset of fatigue is rapid rather than months or years required to the onset of work related musculoskeletal disorders (WMSDs). The objectives of this study were to estimate LMF and quantify muscle activity of select forearm muscles during simulations of high pressure cleaning lance tasks common in the chemical production industry. Twenty participants, twelve males and eight females, with no musculoskeletal injuries and meeting criteria for upper extremity fitness, performed the simulated task. Independent variables studied include work height (shoulder, waist, and knuckle), lance orientation (parallel to the operator and parallel to the ground), and duty cycle (33, 50, and 67%) based on task analyses of actual work tasks. Dependent variables included mean RMS and rates of change in mean RMS, mean and median power frequency, MVE, and subjective ratings of fatigue. Repeated measures ANOVA was used to test the main effects of the independent variables and appropriate interactions. In general it was found that working at waist height, at higher duty cycles, and with the lance oriented parallel to the operator resulted in higher fatigue measures. Subjective ratings of fatigue were not well correlated with objective measures, similar to findings in previous studies. The simulated task was found to be extremely fatiguing and modifications to task design or job rotation schedules are required to reduce risk associated with injury development.