Musculoskeletal injury (MSI) as define by Part 4, section 4.46 of the Occupational Health and Safety Regulation of as an injury or disorder of the muscles, tendons, ligaments, joints, nerves, blood vessels or related soft tissue including a strain, sprain and inflammation, that may be caused or aggravated by work.
Musculoskeletal injury (MSI) has become, a common type of injury in the workplace resulting in lost in productivity in many industries.
There are a number of ergonomic tools available for assessing the risk of musculoskeletal injury. Of these tools, I have decided to focus and discuss three (3), they are:-
Rapid entire body assessment (REBA) was developed by Sue Hignett and Lynn McAtamney as a postural analysis system sensitive to musculoskeletal risks in a variety of tasks. It divides the body into segments to be coded individually with reference to movement planes. It provides a scoring system for muscle activity caused by static, rapid changing, dynamic or unstable postures.
REBA works by observing positions of individual body segments. The more deviations from the neutral posture, the higher the score of each body part. There are two (2) groups that are combined, group A includes trunk, neck and legs and group B upper and lower arms and legs. The 144 posture combinations are transformed to a general postural score. Additionally, load handed, coupling with the local handled and physical activity are observed and scored. These scores are total up to have one score for each observation and then compared to tables stating risk on five levels (negligible – very high) and actions needed (none – necessary now).
Quick Exposure Check (QEC) is scored by assigning values to a number of ‘Observer’ and ‘Worker’ factors. For each of four body parts (back, shoulder, wrist and neck), several pairs of variables are fed into a lookup table to produce a series of sub-scores that are then totaled to produce a score for that body part. You can assess both manual handling and non-manual handling tasks which do not involve back movement.
QEC follows five (5) steps:
Step 1 – Self Training – first time users must read the User Guide to understand the terminology and assessment categories that are used in the check-list.
Step 2 – Observer’s Assessment Check-list – the person observing a particular task uses the observer’s assessment check-list to conduct a risk assessment. One complete work cycle is observed before making an assessment. If a task cannot easily be broken down into tasks, the ‘worst’ event within that job when a particular body part in question is most heavily loaded should be observed. The assessment can be carried out by direct observation or by using video footage.
Step 3 – Worker’s Assessment Check-list – the worker being observed must complete the ‘workers assessment’ check-list.
Step 4 – Calculation of Exposure Scores – using the ‘table of exposure scores’ to calculate the exposure scores for each task.
Circle all the letters corresponding to the answers from the ‘observer’s assessment’ and the ‘worker’s assessment’.
Mark the numbers at the crossing point of every pair of circled letters.
Calculate a total score for each body part.
Step 5 – Consideration of Actions – QEC quickly identifies the exposure levels for the back, shoulder, arm, wrist, hand and neck and it evaluates an ergonomic interventions can effectively reduce these exposure.
2.3 Ovako Working Posture Analysis System – OWAS
Ovako Working Posture Analysis System (OWAS) is a method of coding the posture of a worker that allows the harmfulness of the posture to be categorized into four (4) action categories of increasing urgency. It is based upon expert judgements of the harmfulness of particular postures. A time based sampling approach can be used with it so that the categorization can take account of the length of time spent in any particular posture (Karhu et al., 1977, 1981, Kivi and Mattila, 1991, Vedder, 1998).
Putting the codes for the four (4) segments in the sequence of back, legs, loads and arms form the overall posture code. A rating system categorizes seventy two (72) different postures in terms of discomfort caused, and the effort on health. Back postures are defined as either straight bent, straight and twisted, or bent and twisted. OWAS identifies the most common work postures for the back, which includes four postures; arms three postures, legs seven postures and the weight of the load handled three categories.
The four (4) action categories listed below shows the health hazards of each work posture or posture combination in the OWAS method on the musculoskeletal system: –
Work postures are considered usually with no particular harmful effect on the musculoskeletal system. No actions are needed to change work postures.
Work postures have some harmful effect on the musculoskeletal system. Light stress, no immediate action is necessary, but changes should be considered in future planning.
Work postures have a distinctly harmful effect on the musculoskeletal system. The working methods involved should be changed as soon as possible.
Postures during work have a high harmful effect on the musculoskeletal system. Solutions should be found immediately to reduce these postures.
2.4 Advantages and Disadvantages of Tools
Provides health and safety practitioners with a user friendly assessment tool with good validity.
Helps persuade organizations to make ergonomic changes.
Involves both the practitioner and the worker in the assessment, thereby providing a fuller understanding of working practices.
It is straightforward, quick and easy to use.
Is compatible with HSE risk assessment.
Hypothetical exposure scores with the suggested ‘action levels’ need validating.
Additional training and practice may be needed for novice users to improve assessment reliability.
Method focuses on physical workplace factors only.
Low cost and an effective method.
If valid or accurate can provide valuable insight into working conditions.
Validity and reliability may be low in relation to specific needs for ergonomic assessment.
Can be biased.
Time consuming (both right and left hand have to be assessed separately).
Enables comparisons with previous research in similar settings.
Easy to use and apply with high reliability in field investigations.
It is suitable to assess dynamic, hazardous working postures of workers while moving about their workstations.
Does not separate right and left upper extremities.
Requires thorough training.
Assessments of neck, elbows and wrists are missing.
Does not consider repetition or duration of the sequential posture.
2.5 Critical Analysis of Tools
REBA, QEC and OWAS are all check-list type tools. The only tools needed to perform this type of assessment are a pencil and paper. All three (3) REBA, QEC and OWAS also exist as computer programs, so you can input data collected straight into the software to calculate the overall score.
REBA can assess posture, load, force and movement frequency whereas, QEC assesses posture, load, force, movement frequency, duration, recovery, vibration, etc. and OWAS only assesses posture, load and force.
REBA, QEC and OWAS use ordinal scoring systems and then combine the scores for different risk factors. REBA and OWAS were design to produce an assessment of the urgency of remedial action for the task being assessed using action categories. QEC has an exact mathematical model implicit in its structure with variations in weighting between factors.
REBA and OWAS are performed by one person who understands how the assessment tool is used, whereas QEC is carried out both by the affected employee and the person doing the assessment.
When performing anyone of these three (3) tools, the user must understand fully the function and terminology used, or the assessment will not be accurate.
OWAS has a wide range of uses but the results can be low in detail. REBA was developed specifically with sensitivity to unpredictable working postures.
REBA does not deal in detail with lower limb position. REBA distinguishes between greater or less than 20 degrees of flexion of the head and neck but not further. Both REBA and QEC create overall scores from a mixture of risk factors specific to the upper limb and to the lower back.
These three (3) techniques (REBA, QEC and OWAS) are easy and quick to use, comprehensive and reliable to assess exposures and can be flexible enough to be applied to a range of jobs.
Observational or subjective judgement techniques such as REBA, QEC and OWAS are not more reliable than direct measurement techniques.
There are a number of tools used in the assessment of musculoskeletal injury in the workplace. It is important to assess these situations in order to prevent injury to workers.
The three tools discussed earlier are a good example of common check-list type tools that can evaluate the risk of musculoskeletal injuries in the workplace in a quantitative way. It is important when choosing an ergonomic tool, that it is right for the job. There is no, best tool for any one job but, one must decide on the best approach to what needs to be done.
Rapid Entire Body Assessment (REBA), Quick Exposure Check (QEC) and Ovako Working Posture Analysis System (OWAS) use ordinal scoring systems and then combine the scores for different risk factors. Rapid Entire Body Assessment (REBA) and Ovako Working Posture Analysis System (OWAS) uses action categories based on four (4) and five (5) point ordinal scales to give an assessment of the urgency of remedial action for the task. While the Quick Exposure Check (QEC) has an exact mathematical model implicit in its structure with variations in weighting between factors.
Even though Quick Exposure Check (QEC) has not yet been validated it has been wildly and frequently used along with Rapid Entire Body Assessment (REBA) and Ovako Working Posture Analysis System (OWAS).
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