Human Factors & Ergonomics Society of Australia nd Annual Conference 6 1 The validity of using quick ergonomics assessment tools in the prediction of developing Workplace Musculoskeletal Disorders. Jennie J Window Postgraduate Student: Occupational Health & Safety Management, University of Adelaide Human Factors & Safety Management Systems, University of South Australia Keywords: Workplace Musculoskeletal Disorders, Rapid Entire Body Assessment, Manual Task Risk Assessment Tool, Stress Satisfaction Offset Questionnaire ABSTRACT The purpose of this study is to test the validity of quick ergonomics assessment tools by comparing the results of the posture risk analysis obtained from the Rapid Entire Body Assessment (REBA) and Manual Task Risk Assessment Tool (ManTRA) with historical injury data from an employer and industry data collected by WorkCover South Australia (now known as WorkSafe SA). Posture related observations have been made of three different work tasks, which were broken down into a total of 8 individual actions. There are issues regarding the accuracy of the data due to the small number of participants (17), and the reluctance of employees to report injuries, especially minor ones. REBA gives an overall assessment of two different body posture areas: Posture 'A' trunk, neck, and legs and Posture 'B' upper arm, lower arm, and wrist. Data interpretation issues arise when using this tool due to the grouping of different body areas such as the trunk and legs. ManTRA gives a more in-depth assessment of the legs, back, shoulder, and arms/wrist by providing individual cumulative risk scores for these body regions. To enable a comparison between REBA and ManTRA results, an assumption was made that all of the body regions for one posture ('A' or 'B') produced the same REBA result. Injury level results (low, medium, high) calculated from the employer injury data were similar to industry injury level results for the back, arms and legs. Results obtained from this study identified that REBA provided similar results to industry injury data for the back region for 6 of the 8 observed actions and shoulder region for of the 8 observed actions. ManTRA calculated higher risk levels than provided by industry injury data for the legs, back and shoulders for 7 of the 8 observed actions and for the arms 5 of the 8 observed actions. Results obtained from the observed worker s Stress Satisfaction Offset Questionnaire indicated that 65% of the test group were not experiencing psychosocial risk factors at work. Further studies are needed into the validity quick ergonomics assessment tools and the accuracy of injury data. Additional studies of larger work groups performing a variety of manual handling tasks should be carried out to compare with industry data and check the validity of these quick ergonomics assessment tools.
Human Factors & Ergonomics Society of Australia nd Annual Conference 6 1. INTRODUCTION The 3/ Statistical Review (WorkCover ) identified that up to 1% of male income injury claims and 1% female income injury claims are due to workplace musculoskeletal disorders. The highest incidence rates for this type of long term injury have been recorded in transport & storage (1.%) and finance (%) for males, while the highest long term injury rates for females were found in manufacturing (1%) and construction (33%).. BACKGROUND Historically, quick ergonomics assessment tools have been developed and used to identify the level of exposure to existing musculoskeletal risk factors in the workplace. REBA was developed to investigate work tasks associated with reported Workplace Musculoskeletal Disorders. ManTRA was originally developed to assist Queensland inspectors in auditing workplaces across all industries for compliance with the Queensland Manual Task Advisory Standard (Burgess- Limerick et al.,, p1.). The Stress Satisfaction Offset Questionnaire was developed by Dr. Martin Shain in collaboration with Health Canada to identify the underlying psychosocial factors effecting health and work capacity (Caple et al., 5. p.7). In an ideal world all person-made workplace musculoskeletal disorder risk factors would be eliminated or engineered out before the work tasks are put into practice. However, in the real world, business owners, supervisors and engineers with little or no knowledge of Workplace Musculoskeletal Disorder risk factors are making decisions about work tasks, machine layout and design. Many small to medium businesses do not have the funds available to employ the services of an Ergonomist, Occupational Therapist, or OHS Professional to design their work areas and tasks. There is a real need for accurate quick ergonomics tools that can be used by the layperson. 3. METHODOLOGY Postures used by seventeen workers performing three different work tasks were observed. The work tasks were broken down into individual actions. For example, the first work task observed was the removal of a small motorised plant (leaf blower) from its wall mounted storage hook. The observations were broken down into individual actions: (a) reaching out and grasping the motorised plant; (b) lifting the motorised plant up to clear the top of the hook; and (c) lowering it down before carrying it out of the storage room. Both REBA and ManTRA were used to identify the worker s potential high risk postures. Figure 1. Grasping leaf blower before lifting. Figure. Lifting leaf blower off storage hook.
Human Factors & Ergonomics Society of Australia nd Annual Conference 6 3 The REBA and ManTRA scores were calculated for each of the three observed different work tasks. The different maximum possible scores obtained for REBA and ManTRA highlighted that it would be impossible to compare the raw data obtained from these different quick ergonomics assessment tools. REBA produces a maximum score of 9 for body region 'A' (trunk, neck, legs) or body region 'B' (arms and wrist). ManTRA produces a maximum score of 5 for each individual body region (arms, legs, back, shoulders). To facilitate the comparing of data obtained from the quick ergonomics assessment tools and the historical injury data, it was decided to convert the raw data results into a ratio of the maximum posture risk values. Transfer of these ratios was then carried out to represent low ( -.3), medium (.31 -.6), high (.61 -.9) or very high (.91-1.) posture risks. Below is an example of the data conversion processes used in the study. In this example the Manual Task Risk Assessment Tool was used to assess two work task actions. The cumulative posture score for each of the four body regions is recorded (Table 1). action legs back shoulder Arms 5 19 16 17 19 6 18 15 17 Table 1. Example of ManTRA cumulative scores for two actions. The scores were then calculated as a ratio of the maximum possible cumulative posture score (Table ). action legs back shoulder Arms 5.76.6.68.76 6.8.7.6.68 Table. Example of Table ManTRA scores converted to a percentage of maximum possible cumulative posture score. The percentages are then allocated a risk level of 1 for low, for medium, 3 for high and for very high (Table 3). This then made it possible to make a comparison between the quick ergonomics assessment tools, industry injury data (South Australian WorkCover Injury Classification: SAWIC), and injury data provided by the employer. ManTRA legs back shoulder Arms Action 5 3 3 3 3 Action 6 3 3 3 3 Industry injury data 1 1 1 Employer injury data 1 1 Table 3. Comparison of risk proposed risk levels between the Manual Task Risk Assessment Tool, industry & employer injury data. The Stress Satisfaction Offset Questionnaire was filled in by the seventeen participants after the observations had started. The results of the questionnaire were used to identify if confounding psychosocial factors were present in the workplace. 3.1 DIFFICULTIES WITH THE METHODOLOGY The workplace musculoskeletal disorder data used for this study has different underlying factors and comes from different areas. The industry injury data refers to SAWIC data collected from recorded long term workplace musculoskeletal disorder lost time injuries. The injury data does not
Human Factors & Ergonomics Society of Australia nd Annual Conference 6 identify the specific work task being carried out when the injury occurred. The employer injury data refers to all workplace musculoskeletal disorder injuries (recorded by the employer of the study participants), both long term and short term, which perform similar work tasks to the ones used in this study. For example, the actions observed for working with the small motorised plant (leaf blower) is performed by both the waste management employees and horticulture employees, but the industry data (SAWIC) was only obtained for the Waste Management Industry. 3.1.1 ACCURACY & INTERPRETATION OF INDUSTRY & EMPLOYER INJURY DATA For the purpose of this study, it is assumed that all workplace musculoskeletal disorder injuries have been reported, and the industry and employer injury data is accurate. However, experience has shown that the rate of reporting minor physical problems is quite low unless encouraged ( Safetyline Institute 1998). Furthermore, many employers discourage the reporting of minor injuries, fearing that it may result in an increase in their injury insurance premiums. A common problem in interpreting data statistics is that sudden-onset injuries (such as sprains and strains resulting from a fall) are often in the same category as gradual-onset injuries diagnosed as some kind of musculoskeletal disorder (Macdonald, p.38). 3.1. ACCURACY OF THE RAPID ENTIRE BODY ASSESSMENT TOOL REBA divides the body up into two separate posture groups (A) trunk, neck and legs; and (B) upper arm, lower arm, and wrist. For the purpose of this study, it was assumed that the overall Posture (A) score was accurate for all of the body regions allocated to this designated posture. In real life, this is unlikely to be true. For example, a high risk posture for the legs does not necessarily translate to a high risk back posture at that point in time.. RESULTS Overall, the Waste Management Industry and employer statistics indicated a low level of risk for workplace musculoskeletal disorders for the legs, back and arms (Graph 1). The industry statistics indicated a medium level of risk for workplace musculoskeletal disorders of the shoulder region. Employer statistics indicated a high level of risk for workplace musculoskeletal disorders of the shoulder region in 5% of the recorded cases and a low level of risk for the other 5% of the cases. Employer vs Industry data 3 1 legs back shoulder arms employer data industry data Graph 1. Risk level comparison of employer and industry injury data. Data from REBA and ManTRA identified higher risk factors for leg injury (Graph ) than the employer and industry data for all of the observed actions. REBA provided similar results to the
Human Factors & Ergonomics Society of Australia nd Annual Conference 6 5 employer and industry injury statistics for the back region for 6 of the 8 observed actions. ManTRA provided higher results than the employer and industry injury statistics for for 6 of the 8 observed actions(graph 3). Potential Leg Injury ManTRA employer REBA SAWIC Graph. Leg Injury risk level comparisons Potential Back Injuries ManTRA employer REBA SAWIC Graph 3. Back Injury risk level comparisons Potential Shoulder Injuries ManTRA employer REBA SAWIC Graph. Shoulder Injury risk level comparisons Data from ManTRA identified higher risk factors for shoulder injury than the employer data 6 of the 8 observed actions and the industry data 7 of the 8 observed actions (Graph ). Data from REBA identified lower risk factors for shoulder injury than the employer and industry of the 8 observed actions (Graph ). ManTRA identified higher risk factors for arm injury than the employer and industry 5 of the 8 observed actions (Graph 5). Data from REBA identified lower risk factors for arm injury than the employer and industry 7 of the 8 observed actions (Graph ).
Human Factors & Ergonomics Society of Australia nd Annual Conference 6 6 Potential Arm Injuries ManTRA employer REBA SAWIC Graph 5. Arm Injury risk level comparisons. DISCUSSION The 3/ South Australian WorkCover Statistical Review identified that up to 1% of male income injury claims and 1% female income injury claims in South Australia are due to workplace musculoskeletal disorders. This statistic is unacceptably high. Many small to medium businesses do not have the funds available to employ the services of an Ergonomist, Occupational Therapist or OHS Professional to design their work areas and tasks. Proactive work must be done to successfully educate business owners, work supervisors, and engineers in identification and reduction of workplace musculoskeletal disorder risk factors. This highlights real need for accurate quick ergonomics tools that could be used by the lay-person after two or three hours training. In this study two of the available quick ergonomics assessment tools, the REBA and ManTRA were compared with both employer and industry injury data to test their validity. Postures used by seventeen workers performing three different work tasks were divided into actions and assessed. The different maximum possible scores for REBA (9) and ManTRA (5) highlighted that it would be impossible to compare the raw data obtained from the different tools. The raw data was calculated into a percentage of the maximum posture risk scores. These percentages were then transformed into a risk rating of low, medium, high or very high. It is doubtful that the historical injury data contains all Workplace Musculoskeletal Disorders. Experience has shown that the rate of reporting minor physical problems is quite low unless encouraged (Safetyline Institute 1998). Also, sprains and strains resulting from a fall are often in the same category as gradual-onset injuries diagnosed as some kind of musculoskeletal disorder (Macdonald, p.38). It is recognised that the employer injury data includes minor and lost time injuries where as the industry data only has lost time injuries. However, for the purpose of this study, it is considered that the data from the employer and the industry have the same reporting mechanisms. Due to the calculated employer injury results (for low, medium, high, and very high) being similar to the industry injury data for the back, arms and legs (Graph 1), it was decided to use only the industry data as a reference point in graphs 6 and 7. REBA gives an overall assessment of two different body posture areas: (A) trunk, neck, and legs and (B) upper arm, lower arm, and wrist. If we are looking to risk assess postures for individual parts of the body validity issues arise when using this tool. This is because of the grouping of different body areas such as the trunk and legs. ManTRA gives a more in-depth assessment of the legs, back, shoulder, and arms/wrist by providing individual cumulative risk scores for these
Human Factors & Ergonomics Society of Australia nd Annual Conference 6 7 body regions. Results obtained from this study identified that REBA provided (a) similar results to industry injury data for the back region 6 of the 8 observed actions and shoulder region of the 8 observed actions and (b) markedly higher risk levels for the legs and arms (Graph 6). REBA vs Industry ManTRA vs Industry 1 5 legs back should arms 1 5 legs back should arms higher same higher same Graph 6. Rapid Entire Body Assessment Graph 7. Manual Task Risk Assessment Tool ManTRA provided higher risk levels than industry data for all body regions (Graph 7). In 5 of the 8 observed actions, the results obtained from ManTRA were at least twice as high as the employer and industry injury data. It is difficult to ascertain if the level of injuries reported in employer and industry data is a true reflection of the real-life situation. Research findings on Musculoskeletal injuries from complex postures published by Mason () identified that in the United Kingdom less than 5% officially reported a work-related injury or illness. However, over 85% experienced work-related symptoms, and 3% reported their lost time from work or work restrictions because of their ailment. Employers with a no blame culture are more likely to have data reflecting real-life situations. If we assume that Mason s findings holds true in the majority of workplaces, what multiplier do we use on the employer and industry data to obtain more accurate, real-life information? For example, if we increase the industry data by 5% (Table ), the recorded risk level increases from level 1 (low) to level (medium) for the legs and shoulder, but remains the same for the back (medium) and the arms (low). risk level legs back shoulder arms current 1 1 1 Table. Proposed posture risk levels if industry data was increased by 5% Potential Leg Injury ManTRA REBA industry Graph 8. Leg Injury risk level comparisons where industry data was increased 5% An example of this is the comparison between the original (Graph ) and the adjusted industry data graph (Graph 8) for REBA postures for leg injuries. Previously, the leg posture risk level for
Human Factors & Ergonomics Society of Australia nd Annual Conference 6 8 REBA was greater than the industry risk level in all observed cases (Graph ). When the industry data is increased by 5%, REBA identified the same posture risk levels as industry statistics for 6 of the 8 observed actions (Graph 8). On the other hand, the findings of ManTRA do not correspond at all with the industry posture risk levels (Graph 8). In Graph, the posture risk ratings of ManTRA only corresponded with the industry posture risk ratings for 1 of the 8 observed actions. 5. CONCLUSION Prevention of workplace musculoskeletal disorders is a far better option than rehabilitation. Quick ergonomics assessment tools which can be used by the lay-person are needed so that owners, supervisors and engineers (who may have little or no knowledge of workplace musculoskeletal disorders) can raise their awareness of and make reasonable decisions regarding workplace musculoskeletal disorder risk factors. The results obtained from the observations made in this study are limited due to both the small number of participants and the similarities in the type of work tasks performed. Additional studies of larger work groups performing a variety of manual handling tasks should be carried out to compare with industry data and check the validity of these quick ergonomics assessment tools. References: Burgess-Limerick, R. Straker, L. Pollock, C. and Egeskov, R. (). Manual Task Risk Assessment Tool (ManTRA) V. http://ergonomics.uq,edu.au/download/mantra.pdf Caple, D. Macdonald, W. & Evans, O. (5) Managing Psychosocial Hazards to Reduce the Risk of Work-related Musculoskeletal Disorders. An interactive Workshop. Centre for Ergonomics and Human Factors, Faculty of Health Sciences, La Trobe University. Macdonald, W (). Workload, stress and psychosocial factors as hazards for musculoskeletal disorders. Journal of Occupational Health Safety - Aust NZ, (1):37-7. Mason (). Musculoskeletal injuries from complex postures. HSE Research Report 67/ SafetyLine Institute (1998). Manual Handling - Self Reporting : Consult with employees and supervisors. www.safetyline.wa.gov.au/institute/level/course17/lecture9/18_3.asp WorkCover () Statistical Review 3/. WorkCover Corporation of South Australia