Ergonomic Analysis of Work Related Musculoskeletal Disorder Risk to Plasterers Working in Ireland
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As a consequence of the organisational nature of the construction industry, and due to the dynamic nature of construction activities, construction workers are exposed to Work Related Musculoskeletal Disorders (WRMSDs) risk factors as an intrinsic part of their daily activities. Plasterers are one of the trades that experience high prevalence rates of the disorders when compared with other trades within the industry. Consequently, the quality of their work is affected. Additionally, due to associated absenteeism and early retirement, and costs associated with treatment, compensation, and insurance costs, the plasterer, their employer, and the economy experience a significant financial burden. Upon developing a research risk assessment protocol, it was used as a guide to develop an assessment methodology to evaluate if plasterers working in Ireland were at an increased risk of developing WRMSDs because of their tasks and working conditions. Psychophysical, physiological, and biomechanical assessment methods were selected based on their suitability to evaluate WRMSD risk. Visual Analogue Discomfort Scales (VADS) was used to evaluate psychophysical stress; Heart Rate Analysis (HRA) was used to evaluate physiological stress, and Electromyography (EMG) was used to evaluate biomechanical stress.. The VADS survey consisted of 100mm linear scales, a body map and questionnaires. It was used as an assessment method on active construction sites to measure subjective qualitative judgments of postural discomfort to determine if plasterers experienced discomfort over the course of a working day and working week. Further analysis of the VADS data was carried out to evaluate if the type of work being carried out, and the type of conditions plasterers worked in, influenced levels of discomfort intensity. Additionally, it was used to provide a snapshot representation of the type of work being carried out, and the type of conditions plasterers work in over a five-day work period. The dependent unit of psychophysical response is intensity of discomfort represented as a measure of millimetres ranging from 0-100mm. Eighteen plasterers participated in the VADS study. HRA and EMG were used to evaluate plasterers¿ responses when carrying out a plastering activity in four simulated working environments. Each environment was set up to represent combinations of independent variables - standing surfaces (e.g. ground, stilts, trestle, and hop-up), plastering surfaces (e.g. wall and ceiling), plastering tasks (e.g. Mix Plaster, Load Mortarboard, Load Hawk, Load Trowel and Plaster), and mortarboard stand heights (e.g. 775mm and 1270mm). HRA was used to evaluate and compare each plasterer¿s physiological response when they carried out a wet-plastering task in each of the four assessment workstations. The dependant variables of physiological response were mean heart rate (bpm), Heart Rate Zone (HRZ) activity, Relative Heart Rate (RHR) and Recommended Rest Period (RRP). EMG analysis was used to evaluate muscle activity levels to evaluate the plasterers¿ biomechanical response of for each for each sub-task for each variable condition. The muscles assessed were the right and left sternocleidomastoid muscles in the neck, right and left trapezius muscles in the shoulder, and the right and left erector spinae muscles in the back. The dependent variable of biomechanical response was mean/maximum muscle activity level represented as a percentage of peak muscle activity. Statistical analysis was carried out to describe details about aspects of the sample population and compare independent variables with dependent variables. The results indicate that in most cases independent variables significantly influences change in the dependent variables and plastering activities and working conditions increase plasterers¿ risk of developing WRMSDs. For example, in the VADS study (psychophysical analysis) it was found that plasterers experienced an increase in perceived discomfort intensity levels over five consecutive workdays. A decline in intensity levels was observed after a period of rest i.e. lunch break or overnight break. In the HRA study (physiological analysis), plasterers experienced the highest physiological stress when carrying out a wet-plastering activity on a wall while standing on the ground and a hop-up, and using a low mortarboard stand. When working on ceiling, plasterers experienced their lowest physiological stress when standing on stilts and using a high mortarboard stand. In the EMG study (biomechanical analysis), activity levels were highest when plasterers worked on a ceiling when compared with working on a wall. The neck muscles had the highest activity level when standing on a trestle, whereas the shoulder and back muscles had the highest activity levels when standing on the ground. The neck, shoulder, and back muscles had the highest activity levels when tasks were carried out when using the low mortarboard stand. The findings from the data analysis were used to provide recommendations for control interventions to minimise the adverse effects that the plastering task and working conditions has on the musculoskeletal system and decrease the probability of plasterers developing WRMSDs.