Development of an ergonomics risk assessment tool for repetitive task assessment (RTRA)

Abstract

BACKGROUND:

Most ergonomics assessment tools for repetitive task have been used in industries which are mainly focused on assessing the biomechanical risk factors that affect musculoskeletal disorders (MSDs) rather than the psychosocial and work environment risk factors.

OBJECTIVE:

To develop a tool for Repetitive Task Risk Assessment (RTRA) and Rapid Upper Limb Assessment (RULA) that can identify biomechanical, physical stress and psychosocial risk factors, prioritize risk reduction action and systematic record keeping.

METHODS:

The study consisted of 2 phases; tool development and evaluation of the contents of risk factors by 7 ergonomic experts and intra-rater and inter-rater reliability and validity tests of the tool by 1 researcher and 9 Thai practitioners to assess 30 repetitive tasks.

RESULTS:

RULA was modified by adding more biomechanical risk, combining psychosocial and work environment risk factors lead to MSD become the first prototype of RTRA. The Item-Objective Congruence Index (IOC) validated 20 items on usability of each step of the RTRA ranged between 0.64 and 0.93. The examination of the overall intra-rater reliability was 0.932 (95% CI: 0.862–0.967) and the overall inter-rater was 0.956 (95% CI: 0.909–0.978).

CONCLUSION:

The tool has high test-retest reliability. There is a suggestion for researchers to understand more on the identification of multiple risk factors in one assessment tool and consider a risk-level rating and scoring for prioritizing risk reduction.

Keywords

Ergonomics risk assessment tool observation method risk prioritization

1 Introduction

Work-related musculoskeletal disorders (WMSDs) are a major occupational health injury and illness globally. Many countries and enterprises have voluntarily implemented ergonomics programs, and developed initiative activities to reduce MSDs [1]. Several studies support corporate ergonomic programs at manufacturing sites. The benefit of these studies has resulted in collaboration and participation among stakeholders, acceptance of ergonomic problems and risks, and improvement in understanding, worker’s occupational health, and significant improvement [2 –5].

The use of ergonomics assessment tools is one of the key elements of an ergonomics program in identifying risk factor(s) and rating the risk level to low, medium, or high risk. These tools allow organizations to reduce manual handling risks and make workplace improvement. The use of an assessment tool is required to provide an intuitive and relatively quick process to screen workplaces for high-risk activities, raise awareness of risk factors, demonstrate the presence of risk, and recommend areas for improvement [6].

A variety of risk assessment tools and methods for assessing and/or preventing the risks of musculoskeletal disorders are available, but not limited to tools, such as Manual handling Assessment Charts (MAC) [7], assessment tool for repetitive tasks of the upper limbs (ART), NIOSH equation, Strain index, Ovako Working Posture Assessment (OWAS), Rapid Upper Limb Assessment (RULA) [8 –10]. Quick Exposure Check (QEC) [11], rapid entire body assessment (REBA), Roger Muscle Fatigue Analysis, and WISHA Caution/Hazard Checklist Modified, Postural Ergonomics Risk Assessment (PERA).

The limitation of these presented assessment tools is that they mainly focus on external load whereas several sources indicate that psychosocial and work environment risk factors are among the main causes of the development of MSDs [12,13, 12,13].

The aim of this study was to develop a new observation method ergonomic assessment tool for repetitive tasks which enables the assessor:

To identify necessary information and risk factors; biomechanical, physical stress, concern and working environment.

To prioritize risk to further take corrective action for manufacturing sites where assessment of many workstations is required.

To systematically record all risk assessment results.

2 Material and methods

There were 2 process steps to develop new assessment tool as shown in Fig. 1.

Fig. 1

RTRA development flow.

2.1 Phase I: Tool development and validity test phase

This phase consists of review of literature, identification of all potential risk factors which cause MSDs, review of ergonomics assessment tools by searching through National Library of Medicine (PubMed), Google Scholar, country codes of practices, and country regulations along with guidance related to human factors or ergonomics, then analyzing those tools to identify limitations and develop a new observation ergonomics assessment tool to achieve the objectives.

2.1.1 Subject

Ten international ergonomic experts from the International Ergonomics Association were invited to perform the validly test of the tool. They had to have at least five years of experience in ergonomics risk assessment for repetitive tasks, physical risk, and/or, cognitive issues and work experience in the ergonomics field either in the private sector, university or government agency, and should be recognized by an ergonomics association in their country of practice. Seven experts accepted and participated in the validity test.

2.1.2 Data collection

The first completed prototype of repetitive task risk assessment (RTRA), a step by-step guide to use the tool and an online usability questionnaire of the tool was sent to the seven international ergonomics experts via email. Ergonomics experts reviewed and tested the tool and then completed an online usability questionnaire and provided their input and suggestions.

2.1.3 Data analysis

Descriptive statistics, number and percentage and the index of item-objective congruence (IOC) for validity usability of the tool [14] were used to evaluate content validity of the tool at development stage.

2.2 Phase II: Reliability and validity of the tool

2.2.1 Subject

Ten Thai ergonomics practitioners from Ergonomics Society of Thailand were recruited to perform the reliability test of the tool. They had to have at least 3 years of experience in ergonomics risk assessment for repetitive tasks, a university background in occupational health and safety, engineering or physiotherapy and work in the ergonomics field in the private sector, university, government agency or ergonomics association in the country. They were approached via email. Nine practitioners accepted and participated in the test.

2.2.2 Data collections

Intra-rater reliability (researcher): In the first round of the assessment, a researcher performed a blind and random video and job description to conduct risk assessment for 30 repetitive tasks by using the 2nd prototype of RTRA and record risk assessment result. The 2nd round assessment, at one month followed first round assessment, the researcher performed blind and random video and job description to conduct risk assessment for the same 30 tasks and record risk assessment result.

Inter-rater reliability test (ergonomics practitioners): All participants were given the rationale and objective of the study and gave informed consent. Then the researcher provided training on how to use the RTRA to the 9 practitioners to ensure that they had the same understanding of how to use the tool. All trained practitioners performed the assessment of the 30 tasks together and recorded the results. All practitioners completed the online usability questionnaire and provided suggestions for tool improvement.

2.2.3 Data analysis

Intraclass correlation coefficient (ICC) for reliability test-retest intrarater and interrater reliability analysis [15] was used with criteria based on the 95% confidence interval of ICC. Values less than 0.5, between 0.5 to 0.75, between 0.75 and 0.9 and greater than 0.90 are indicative of poor, moderate, good and excellent reliability respectively. The evaluation of reliability and validity is essential for the development of the exposure assessment method [11].

3 Results

3.1 Phase I: Tool development and validity test phase

3.1.1 Cause of MSD and limitation of assessment tools

Occupational health and safety and/or human factors and ergonomics related books, articles, government reports, several studies have indicated that WMSDs are associated with the following factors [16–19 , 20]: 1) personal factor; age, gender, height, dominant hand, smoking, alcohol, education, number of children, hobbies, sport and medical history, 2) biomechanical risk; awkward posture, repetitiveness statics efforts, previous workload especially when occurring at high levels or in combination [11 , 21–25], 3) physical stress; compression or contact stress, excessive vibration, working in cold or hot temperatures, use of personal protective equipment, low or high levels of lighting, glare or reflection, high noise level and long work hours [6 , 26–28] and 4) psychoorganizational factors and psychosocial factor, monotony, time pressure, lack of social support, work dissatisfaction, mental stress, lack of or poor communication, perception of low support from supervisor or coworker, incentives to skip breaks or finish early, high levels of attention and concentration, and insufficient training to do the job successfully.

There was evidence to support that the interaction between physical and psychosocial risk factors in the workplace increase the risk of reporting symptoms in the upper limbs. Psychosocial risk factors at work were more important when exposure to physical risk factor at work were higher than when physical exposure was low and suggested that ergonomic intervention strategies that aim to minimize the risks of work-related MSDs should not only focus on physical but also on psychosocial work factors [29, 30]. Moreover, the moden assessment approaches should address both physical and organizational aspects of the work environment, and consider the context complexities in which the worksites and the industry operate [31].

Four observation methods for repetitive task risk assessment most frequently used by practitioners were RULA, REBA, OWAS [32] and QEC [33]. The essential information and all risk factors contained in the tool were reviewed and analyzed to identify limitation and area where modification would better suit repetitive tasks and identify all risk factors in workplace as shown in Table 1.

Table 1
Comparison of the elements and risk factors of four observation assessment tools

Required information and all risk factors cause MSD Required information, risk factors are available in the assessment tool and limitation

RULA REBA QEC OWAS

1. General information of the job to be assessed Yes Yes Yes Yes

2. Biomechanical risk–Awkward posture–Frequency–Duration–Force/ load Yes, but do not cover foot and can evaluation only one site of body Yes, but do not cover foot and can evaluation only one site of body Yes, but do not cover leg, foot and can evaluation only one site of body Yes, but do not cover neck, hand & wrist

3. Physical stressor–Vibration–Soft tissue compression–Long work-hour–Wearing personal protective equipment No No Yesonly vibration and long work-hour but do not cover soft tissue compression, and wearing PPE Yesonly long work-hour but do not cover vibration soft tissue compression, and wearing PPE

4. Known ergonomics risk factor and there was WMSD case reported No No No No

5. Psychosocial risk factor concern from worker No No Yes No

6. Work environment–Cold temperature–Humidity–Lighting–Noise No No Yes No

7. Risk rating–Risk score for each body part–Comparing risk first and second round after intervention implementation–Overall risk rating Yesbut left and right side of body part are assessed indepently, do not have risk comparison Yesbut left and right side of body part are assessed indepently, do not have risk comparison Yesbut left and right side of body part are assessed indepently Yesbut do not have risk comparison

8. Prioritizing risk No No No No

9. Systematic record keeping No No No No

Required information and all risk factors cause MSD	Required information, risk factors are available in the assessment tool and limitation
	RULA	REBA	QEC	OWAS
1. General information of the job to be assessed	Yes	Yes	Yes	Yes
2. Biomechanical risk–Awkward posture–Frequency–Duration–Force/ load	Yes, but do not cover foot and can evaluation only one site of body	Yes, but do not cover foot and can evaluation only one site of body	Yes, but do not cover leg, foot and can evaluation only one site of body	Yes, but do not cover neck, hand & wrist
3. Physical stressor–Vibration–Soft tissue compression–Long work-hour–Wearing personal protective equipment	No	No	Yesonly vibration and long work-hour but do not cover soft tissue compression, and wearing PPE	Yesonly long work-hour but do not cover vibration soft tissue compression, and wearing PPE
4. Known ergonomics risk factor and there was WMSD case reported	No	No	No	No
5. Psychosocial risk factor concern from worker	No	No	Yes	No
6. Work environment–Cold temperature–Humidity–Lighting–Noise	No	No	Yes	No
7. Risk rating–Risk score for each body part–Comparing risk first and second round after intervention implementation–Overall risk rating	Yesbut left and right side of body part are assessed indepently, do not have risk comparison	Yesbut left and right side of body part are assessed indepently, do not have risk comparison	Yesbut left and right side of body part are assessed indepently	Yesbut do not have risk comparison
8. Prioritizing risk	No	No	No	No
9. Systematic record keeping	No	No	No	No

The analysis found all four tools contained common key elements; the job to be assessed, mainly focused on biomechanical risk identification and risk rating, and did not adequately allow to cover all elements.

RULA and REBA did not have physical stressor, known ergonomics risk factors, psychosocial risk, work environment, risk prioritization and systematic record keeping. QEC did not have known ergonomics risk factors, risk prioritization and systematic record keeping and OWAS did not have known ergonomics risk factors, psychosocial risk, work environment, risk prioritization and systematic record keeping.

A comparison of three observational techniques for assessing postural loads in industry, overall, OWAS and REBA were less sensitive to postural stress than RULA and OWAS and REBA underestimated postural load for the considered postures compared to RULA [8]. RULA and REBA were mainly applied to workers in manufacturing, REBA is not useful for the evaluation of repetitive movements [34, 35] and RULA can identify all information needed by ergonomist and practitioner and was widely used [10]. Finally, RULA was identified as the most suitable ergonomics assessment tool for modification and develop the new assessment tool.

The study researcher wrote to Dr. Lynn McAtamney (the developer and owner of the RULA tool) to gain permission to use and modify the RULA tool to specifically further develop RULA to enable identifying necessary information and risk factors; biomechanical, physical stress, concern and working environment, prioritizing risk in order to further take corrective action for manufacturing sites where assessment of many workstations is required, systematically recording all risk assessment results. Dr. McAtamney granted permission on 5 April2017.

3.1.2 Assessment tool base on RULA development

The background, objectives, and benefits of this study was discussed with a software and graphic designer to determine the possibility to develop a new assessment tool per the risks and required information then the ergonomic risk assessment tool called RTRA was developed as a software, application, or stand-alone program on Microsoft. Net Framework 4.0 or above by a software and graphic designer.

The RTRA contains 4 major steps: Step 1 Review task information, Step 2 Risk identification, Step 3 Physical stress and concerns, Step 4 Assessment Scoring before (first) and after(second) implementing intervention and total score. The RTRA provides two types of risk: 1) biomechanical risk and 2) physical, work environmental and psychosocial risk. Assessment flow is shown in Fig. 2.

Fig. 2

RTRA scoring layout.

The following modifications were undertaken allowing RTRA to identify all necessary information and risk factors, prioritizing risk for taking further corrective action and recording all risk assessment result systematically which able to close all gaps identified in item 3.1.1.

3.1.2.1 Assessment step

Step 1: Job information, a number of similar exposure group involved in the assessment task was added.

Step 2: Biomechanical risk assessment

Awkward posture by adjusting and adding risk, covering all body part left and right side [34], scoring of before and after taking action for comparison, a clearer criterion for degree of awkward posture for

Step 2.1 Upper arm position. Added picture of 2.1. Adjusted shoulder is raised, upper arm is abducted, arm is support or person is leaning.

Step 2.2 Lower arm position. No changes made.

Step 2.3 Wrist position. No changes made.

Step 2.4 Wrist twist position. No changes made.

Step 2.5 Arm posture score in Table A. No changes made.

Steps 2.6 and 2.13 Muscle use score. Frequency by adjusting frequency of upper arm, lower arm, neck, back and leg.

Frequency > 2 times/ minute can cause MSD at shoulder, elbow, lower arm, neck, back and leg: Exposure to repetitive task with short (<30 seconds) cycles caused worker reported neck/ shoulder, hand and wrist pain/ symptom(s) [36 –39].

Frequency > 20 times/ minute can cause MSD at hand and wrist [11].

Steps 2.7 and 2.14 Load/Force score. No changes made.

Step 2.8 Arm, Wrist score. No changes made.

Step 2.9 Neck position. Added picture of 2.9. Adjust if neck is twisted, if neck is side bending and made it clearer on degree of bending at more than 20 degrees [27].

Step 2.10 Trunk position. Added picture of 2.10. Adjust if trunk is twisted, if trunk is side bending and made it clearer on degree of bending at more than 20 degrees [27]. Trunk or back unsupported. Sitting for a prolonged period on chairs that does not provide adequate lumbar support, or if there is no back rest the muscles of the back are trying to force the lumbar region out of its natural curve, which places pressure on the discs and reduces blood supply to the spinal tissue and muscle fatigue [24].

Step 2.11 Leg position. Added picture of 2.11. Adjust if legs and feet are supported, unsupported. Added new risks posture, no legs space, upper leg to body>,<90 degrees [40].

Step 2.12 Trunk posture score in Table B. No changes made.

Step 2.15 Neck, trunk, leg score. No changes made.

Step 3: Physical stressor, concerns, and work environment

Step 3.1 Work to be performed if > 8 hours more ergonomic risk [6,28,41 , 6,28,41] by adding+1 score.

Step 3.2 Known ergonomics risk factor and if there was WMSD case reported associated with the task be assessed by adding+2 score for WMSD case reported within x months means risk is already there but there is no action taken.

Step 3.3 Psychosocial risk factor by adding + 1 score for concerns from worker who involve the task on potential to have discomfort or MSD while and after performing the task, mental requirement, monotony, high work rate, time pressure, excessive work demands; high levels of attention and concentration, and insufficient training to do the job successfully, etc.

Step 3.4 Excessive vibration by adding + 1 score.

Step 3.5 Cold temperature mean working environment temperature is at least 16 degrees Celsius [42] by adding + 1 score.

Step 3.6 Lighting low or high levels of lighting, glare or reflect [43] may lead to awkward or sustained postures to improve vision or to avoid glare by adding + 1 score.

Step 3.7 Excessive noise cause headaches and increase blood pressure, muscle tension and fatigue [44,45, 44,45] by adding + 1 score.

Step 3.8 Tissue compression by adding + 1 score

Step 3.9 Wearing PPE such as glove or other by adding + 1 score. PPE such as wearing gloves which are too large, too small, or bulky for the user’s hand. It often leads to using more muscle force than would be required without gloves [9,17, 9,17].

Step 4 Assessment scoring. Risk rating, scoring and action level recommendation.

3.1.3 Assessment scoring system

The RTRA provides two types of risk; 1) biomechanical risk and 2) physical, work environmental and psychosocial risk level and then both are combined to overall risk level. Breaking these into two areas of risk allows the user to focus future corrective actions on the specific identified risk issue. Risk rating and scoring system of biomechanical risk referred to RULA, it can be used even adding more risk into each assessment step resulted not required to modify.

There was insufficient information to reference in risk rating and scoring for physical, work environmental and psychosocial risk. This study proposed if found any risk, one score is weighted and two score weighted for known as WMSD case reported at the assessed operation. And investigation and action are required if any risk was identified.

RTRA computerized system was developed to automatically calculate risk ratings, which provides uniformity, standardized an accurate calculation, and time efficiencies. The risk rating for considering action of both types is indicated below

3.1.3.1 Biomechanical risk level

Score 1-2 Green – Acceptable risk, no action required.

Score 3-4 Yellow – Low risk, further investigation and change may be needed.

Score 5-6 Orange – Medium risk which requires further investigation or change soon.

Score above 6 Red – High risk which required change as soon as possible.

3.1.3.2 Physical stress, work environment and psychosocial risk level (illustrated in Step 3)

Score 1 Orange – requires further investigation and change based on investigation results.

Score 2 Red – required further investigation and changes are required immediately regarding the high risk that resulted whenever a confirmed work-related musculoskeletal disorder was reported.

3.1.3.3 Overall risk level of RTRA – the RTRA scoring system combines the total score of biomechanical plus physical stress, work environment and psychosocial risk levels and applies an overall color code risk score as above based on the risk present after completing Step 2 of the risk assessment.

RTRA combines the risk identified in Step 2 and Step 3 to produce a grand total score, as shown in Table 2. The process illustrates a minimum and maximum score and trigger score of the above step. The table reminds the user to consider issue if an investigation and focus on the driving cause of potential MSD. The trigger score comes from at least two risks such as posture and frequency or posture and duration which can cause MSD to that body part.

Table 2
Minimum, maximum and trigger risk score for considering action

Assessment step Possible score Trigger score Recommendation action

Min. Max.

Step 2 Posture, duration, frequency force/ load risk assessment

Step 2.5 Posture score in table A 1 9 4 It is possible to exposure to a combination risk from posture, frequency, load which can contribute to MSD

Step 2.8 Wrist arm score 1 15 4

Step 2.12 Trunk posture score in table B 1 9 5

Step 2.15 Neck, trunk and leg score 1 14 4

Step 3 Physical stress and concerns

Step 3 Physical stress and concerns 0 10 1 Required investigation and take action based on root cause identified

Step 4 Assessment scoring

Total score (left, right) of Step 2 1 7

Grand total score (total score+Step 3) 1 17

Assessment step	Possible score	Trigger score	Recommendation action
Step 2 Posture, duration, frequency force/ load risk assessment
Step 2.5 Posture score in table A	1	9	4	It is possible to exposure to a combination risk from posture, frequency, load which can contribute to MSD
Step 2.8 Wrist arm score	1	15	4
Step 2.12 Trunk posture score in table B	1	9	5
Step 2.15 Neck, trunk and leg score	1	14	4
Step 3 Physical stress and concerns
Step 3 Physical stress and concerns	0	10	1	Required investigation and take action based on root cause identified
Step 4 Assessment scoring
Total score (left, right) of Step 2	1	7
Grand total score (total score+Step 3)	1	17

3.1.4 Assessment result record keeping

At manufacturing sites, there are many hundreds of manual handling tasks, RTRA was developed to assist user by gathering the results of assessment and rating them so that the user can prioritizing intervention and the order of implementation.

Moreover, RTRA was developed to assist users with record keeping in soft copy. Doing this allows user to revise, perform re-evaluation after intervention implementation and update the risk history. This can be achieved by simply opening the file and updating the result to compare risk levels before and after.

RTRA software had been reviewed, revised, and refined many times. The major issues that have been discussed often were the need for clearer illustration to ensure users understand clearly, the illustration and auto calculation score to be precise and accurate.

3.1.5 Step-by-step instruction how to use the RTRA and training material development

The step-by-step guide was developed after the 1st prototype development completion and trial. The training material was created after the 2nd prototype development was completed. The RTRA guide in Appendix A provides users information on how to get the RTRA assessment system, download RTRA system into a computer and adjust computer screen, pre-assessment of the task and video record and steps to complete the RTRA.

3.1.6 RTRA questionnaire development

A questionnaire was developed using Google Docs to allow panelists to complete questionnaires effectively and efficiently for getting agreement and input from the ergonomics panelists that each stage of development. The questionnaire consists of 25 questions as shown in Appendix B. Question 1–3 ask about participant’s information, email address, organization, and country they were living and working. Question 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24 ask for their agreement and input to assist with the development of the RTRA. There are 4 levels of agreement; totally agree, partially agree, partially disagree, and totally disagree. Question 5, 7, 9, 11, 13, 15, 19, 21, 23, 25 ask participants for suggestions to improve content of the RTRA tool in question 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24 respectively. Question 17 asked if the illustrations of body parts neededimprovement.

3.1.7 RTRA validity test by ergonomics panelists and tool improvement

The Item-Objective Congruence Index (IOC) was set to validate 20 items on the tool’s usability and the process flow. The questionnaire provided four potential values; Disagree, Partially Disagree, Partially Agree, and Totally Agree for each item. The twenty IOC indicated between 0.64 and 0.93.

Each question scored higher than 0.5; which indicated that the panelists confirmed each as appropriate to assess the repetitive task ergonomics risk assessment. The highest group IOC scores showed between 0.86–0.93 as shown in Table 3.

Table 3
The validation results of RTRA by ergonomic experts

Usability questionnaire Totally agree n(%) Partially agree n(%) Partially disagree n(%) Disagree n(%) IOC

1. The tool is able to identify details of job information. 5 (71.4) 2 (28.6) 0 0 0.86

2. The tool is able to identify risk specific on body part (left and right side). 4 (57.1) 3 (42.9) 0 0 0.79

3. The tool is able to identify risk on duration of exposure. 3 (42.9) 4 (57.1) 0 0 0.71

4. The tool is able to identify frequency of exposure “>2.5x/minute can cause MSD at shoulder”. 5 (71.4) 1 (14.3) 0 1 (14.3)¹ 0.71

5. The tool is able to identify risk on physical stress exposure. 5 (71.4) 2 (28.6) 0 0 0.86

5.1 Work hour > 8 hours 4 (57.1) 3 (42.9) 0 0 0.79

5.2 WMSD case reported 4 (57.1) 3 (42.9) 0 0 0.79

5.3 Ergo concerns 4 (57.1) 2 (28.6) 0 1 (14.3)² 0.64

5.4 Vibration 4 (57.1) 3 (42.9) 0 0 0.79

5.5 Cold and hot temperature 4 (57.1) 2 (28.6) 1 (14.3)³ 0 0.64

5.6 Tissue compression 4 (57.1) 3 (42.9) 0 0 0.79

5.7 Glove too large or too small 4 (57.1) 2 (28.6) 0 1 (14.3)⁴ 0.64

6. The tool contain a clear picture of posture. 5 (71.4) 2 (28.6) 0 0 0.86

7. The tool is able to identify risk factor on force and load. 5 (71.4) 2 (28.6) 0 0 0.86

8. The tool is able to provide overall risk rating for prioritizing action. 5 (71.4) 2 (28.6) 0 0 0.86

9.1 A step-to-step guide to assessment tool ease to understand. 6 (85.7) 1 (14.3) 0 0 0.93

9.2 Will you use the new assessment tool for repetitive task? 5 (71.4) 1 (14.3) 0 1 (14.3)⁵ 0.71

9.3 All risk assessment result able to be kept? 5 (71.4) 1 (14.3) 0 1 (14.3)⁶ 0.71

10.1 The assessment tool is benefit to use. 5 (71.4) 2 (28.6) 0 0 0.93

10.2 Will you recommend ergonomics practitioners use this new tool for their further assessment? 5 (71.4) 2 (28.6) 0 0 0.93

Usability questionnaire	Totally agree n(%)	Partially agree n(%)	Partially disagree n(%)	Disagree n(%)	IOC
1. The tool is able to identify details of job information.	5 (71.4)	2 (28.6)	0	0	0.86
2. The tool is able to identify risk specific on body part (left and right side).	4 (57.1)	3 (42.9)	0	0	0.79
3. The tool is able to identify risk on duration of exposure.	3 (42.9)	4 (57.1)	0	0	0.71
4. The tool is able to identify frequency of exposure “>2.5x/minute can cause MSD at shoulder”.	5 (71.4)	1 (14.3)	0	1 (14.3)*¹	0.71
5. The tool is able to identify risk on physical stress exposure.	5 (71.4)	2 (28.6)	0	0	0.86
5.1 Work hour > 8 hours	4 (57.1)	3 (42.9)	0	0	0.79
5.2 WMSD case reported	4 (57.1)	3 (42.9)	0	0	0.79
5.3 Ergo concerns	4 (57.1)	2 (28.6)	0	1 (14.3)*²	0.64
5.4 Vibration	4 (57.1)	3 (42.9)	0	0	0.79
5.5 Cold and hot temperature	4 (57.1)	2 (28.6)	1 (14.3)*³	0	0.64
5.6 Tissue compression	4 (57.1)	3 (42.9)	0	0	0.79
5.7 Glove too large or too small	4 (57.1)	2 (28.6)	0	1 (14.3)*⁴	0.64
6. The tool contain a clear picture of posture.	5 (71.4)	2 (28.6)	0	0	0.86
7. The tool is able to identify risk factor on force and load.	5 (71.4)	2 (28.6)	0	0	0.86
8. The tool is able to provide overall risk rating for prioritizing action.	5 (71.4)	2 (28.6)	0	0	0.86
9.1 A step-to-step guide to assessment tool ease to understand.	6 (85.7)	1 (14.3)	0	0	0.93
9.2 Will you use the new assessment tool for repetitive task?	5 (71.4)	1 (14.3)	0	1 (14.3)*⁵	0.71
9.3 All risk assessment result able to be kept?	5 (71.4)	1 (14.3)	0	1 (14.3)*⁶	0.71
10.1 The assessment tool is benefit to use.	5 (71.4)	2 (28.6)	0	0	0.93
10.2 Will you recommend ergonomics practitioners use this new tool for their further assessment?	5 (71.4)	2 (28.6)	0	0	0.93

The ergonomics panel’s suggestions were reviewed, and modification was made to the tool. Modifications were made to the step-by-step guidance which were enhanced and refined, and the tool became prototype II. The 2nd prototype was then shared with 3 of the panel for review. The panelists acknowledged and agreed with the revision.

Overall, comments and suggestion from panelists and improvement lead to the final tool being more beneficial and user-friendly.

3.2 RTRA reliability test by a researcher, practitioners, and improvement

3.2.1 A comparison of the assessment score between two times assessment by the researcher

Researcher conducted the risk assessment twice one month apart. Thirty randomly selected repetitive tasks were selected from the participating Thailand based electronic manufacturing site. The user reviewed job information and completed risk assessment.

The results of intra-observer of both the first and second assessment are presented in Table 4. The overall intra-observer reliability was 0.932 (95% CI: 0.862–0.967). Left and the right posture assessment score on part 4.1 and 4.2 were 0.90 (95% CI: 0.80–0.95), and 0.93 (95% CI: 0.87–0.97). Neck, trunk, and leg score left, and right side were 1.00 (95% CI:1.00–1.00). Trunk posture score on the left and the right side in step 2.12, and 2.12 were 0.86 (95% CI: 0.73–0.93) and 0.84 (95% CI: 0.687–0.919) respectively. These results showed very good consistency [15] between the two RATA assessmentscore.

Table 4
Intraclass reliability test by Researcher 2 times

Assessment steps Agreement between Researcher 1st and 2nd time evaluation number (%) Disagreement between Researcher 1st and 2nd time evaluation number (%) Mean time 1±SD Mean time 2±SD Intra ICC p-value of risk score

Wrist, arm posture score left 18 (60.0%) 12 (40.0%) 4.63±1.066 4.60±0.894 .734a (0.512–0.864) 0.000

Wrist, arm posture score right 18 (60.0%) 12 (40.0%) 5.00±1.145 4.93±0.868 .601a (0.313–0.788) 0.000

Wrist arm score left 18 (60.0%) 12 (40.0%) 5.67±1.269 5.70±0.952 .685a (0.436–0.837) 0.000

Wrist arm score right 16 (53.3%) 14 (46.7%) 6.10±1.398 6.10±0.885 .572a (0.272–0.770) 0.000

Trunk posture score left 21 (70.0%) 9 (30.0%) 4.67±1.971 5.07±1.701 0.862a (0.730–0.932) 0.010

Trunk posture score right 21 (70.0%) 9 (30.0%) 4.73±1.982 5.03±1.712 .838a (0.687–0.919) 0.000

Neck, trunk and leg score left 23 (76.7.0%) 7 (23.3%) 5.80±1.846 6.03±1.810 1.000a (1.00–1.00) 0.000

Neck, trunk and leg score right 22 (73.3%) 8 (26.7%) 5.87±1.852 6.00±1.819 1.000a (1.00–1.00) 0.000

Posture assessment score left 24 (80.0%) 6 (20,0%) 6.27±1.015 6.40±0.932 .901a (0.802–0.951) 0.000

Posture assessment score right 27 (90.0%) 3 (10.0%) 6.40±0.855 6.50±0.820 0.934a (0.870.97) 0.000

Total assessment score 25 (83.3%) 5 (16.7%) 8.07±1.048 8.23±1.006 .932a (0.862–0.967) 0.000

Assessment steps	Agreement between Researcher 1st and 2nd time evaluation number (%)	Disagreement between Researcher 1st and 2nd time evaluation number (%)	Mean time 1±SD	Mean time 2±SD	Intra ICC	p-value of risk score
Wrist, arm posture score left	18 (60.0%)	12 (40.0%)	4.63±1.066	4.60±0.894	.734a (0.512–0.864)	0.000
Wrist, arm posture score right	18 (60.0%)	12 (40.0%)	5.00±1.145	4.93±0.868	.601a (0.313–0.788)	0.000
Wrist arm score left	18 (60.0%)	12 (40.0%)	5.67±1.269	5.70±0.952	.685a (0.436–0.837)	0.000
Wrist arm score right	16 (53.3%)	14 (46.7%)	6.10±1.398	6.10±0.885	.572a (0.272–0.770)	0.000
Trunk posture score left	21 (70.0%)	9 (30.0%)	4.67±1.971	5.07±1.701	0.862a (0.730–0.932)	0.010
Trunk posture score right	21 (70.0%)	9 (30.0%)	4.73±1.982	5.03±1.712	.838a (0.687–0.919)	0.000
Neck, trunk and leg score left	23 (76.7.0%)	7 (23.3%)	5.80±1.846	6.03±1.810	1.000a (1.00–1.00)	0.000
Neck, trunk and leg score right	22 (73.3%)	8 (26.7%)	5.87±1.852	6.00±1.819	1.000a (1.00–1.00)	0.000
Posture assessment score left	24 (80.0%)	6 (20,0%)	6.27±1.015	6.40±0.932	.901a (0.802–0.951)	0.000
Posture assessment score right	27 (90.0%)	3 (10.0%)	6.40±0.855	6.50±0.820	0.934a (0.870.97)	0.000
Total assessment score	25 (83.3%)	5 (16.7%)	8.07±1.048	8.23±1.006	.932a (0.862–0.967)	0.000

3.2.2 A comparison of assessment results between the researcher and the practitioners

The consistency of the RTRA tool was reviewed between researcher and nine Thai ergonomics practitioners. All the Thai ergonomics practitioners had received training in the RTRA tool prior to them taking part in the assessments. The results of inter-rater reliability are presented in Table 5. The overall inter-observer reliability was 0.95 (95% CI: 0.90–0.97). Left and the right posture assessment score on part 4.1 and 4.2 were 0.95 (95% CI: 0.90–0.97) and 0.85 (95% CI: 0.72–0.93).

Table 5
Inter-rater reliability test for RATA assessment score between ergonomic practitioner and researcher

Assessment step Agreement between practitioner and researcher number (%) Disagreement between practitioner and researcher number (%) Practitioner mean (SD) Researcher mean (SD) ICC p-value of risk score

Arm, wrist posture score left 17 (56.7) 13 (43.3) 4.67±1.12 4.60±0.89 .735a (0.5141–0.8644) 0.000

Arm, wrist posture score right 15 (50.0) 15 (50.0) 5.10±1.21 4.93±0.87 .471a (0.1390–0.7076) 0.0004

Wrist arm score left 17 (56.7) 13,0(43.3) 5.77±1.22 5.70±0.95 .772a (0.5748–0.8847) 0.000

Wrist arm score right 16 (53.3) 14,0(46.7) 6.23±1.36 6.10±0.88 .560a (0.2559–0.7633) 0.001

Trunk posture score left 23 (76.7) 7,0(23.3) 4.77±1.77 1.03±0.18 0.873 (0.7501–0.9373) 0.000

Trunk posture score right 24 (80.0) 6 (20.0) 4.87±1.76 5.03±1.71 .953a (0.9041–0.9774) 0.000

Neck, trunk and leg score left 25 (83.3) 5 (16.7) 5.80±1.79 6.03±1.81 .886a (0.7750–0.9442) 0.000

Neck, trunk and leg score right 26 (86.7) 4 (13.3) 5.90±1.77 6.00±1.82 0.964 (0.926–0.983) 0.000

Posture Assessment Score Left 23 (76.7) 7 (23.3) 6.30±0.88 6.40±0.93 .859a (0.7250–0.9303) 0.000

Posture assessment score right 28 (93.3) 2 (6.7) 6.43±0.86 6.50±0.82 0,954 (0.9064–0.9780) 0.000

Total assessment score 27 (90.0) 3 (10.0) 8.13±1.04 8.23±1.01 .956a (0.9090–0.9786) 0.000

Assessment step	Agreement between practitioner and researcher number (%)	Disagreement between practitioner and researcher number (%)	Practitioner mean (SD)	Researcher mean (SD)	ICC	p-value of risk score
Arm, wrist posture score left	17 (56.7)	13 (43.3)	4.67±1.12	4.60±0.89	.735a (0.5141–0.8644)	0.000
Arm, wrist posture score right	15 (50.0)	15 (50.0)	5.10±1.21	4.93±0.87	.471a (0.1390–0.7076)	0.0004
Wrist arm score left	17 (56.7)	13,0(43.3)	5.77±1.22	5.70±0.95	.772a (0.5748–0.8847)	0.000
Wrist arm score right	16 (53.3)	14,0(46.7)	6.23±1.36	6.10±0.88	.560a (0.2559–0.7633)	0.001
Trunk posture score left	23 (76.7)	7,0(23.3)	4.77±1.77	1.03±0.18	0.873 (0.7501–0.9373)	0.000
Trunk posture score right	24 (80.0)	6 (20.0)	4.87±1.76	5.03±1.71	.953a (0.9041–0.9774)	0.000
Neck, trunk and leg score left	25 (83.3)	5 (16.7)	5.80±1.79	6.03±1.81	.886a (0.7750–0.9442)	0.000
Neck, trunk and leg score right	26 (86.7)	4 (13.3)	5.90±1.77	6.00±1.82	0.964 (0.926–0.983)	0.000
Posture Assessment Score Left	23 (76.7)	7 (23.3)	6.30±0.88	6.40±0.93	.859a (0.7250–0.9303)	0.000
Posture assessment score right	28 (93.3)	2 (6.7)	6.43±0.86	6.50±0.82	0,954 (0.9064–0.9780)	0.000
Total assessment score	27 (90.0)	3 (10.0)	8.13±1.04	8.23±1.01	.956a (0.9090–0.9786)	0.000

Neck, trunk, and leg score left, and right side were 0.88 (95% CI: 0.77–0.94) and 0.96 (95% CI: 0.92–0.98). Trunk posture score on the left and the right side in step 2.12, and 2.12 were 0.87 (95% CI: 0.75–0.93) and 0.95 (95% CI: 0.90–0.97) respectively. These results showed very good consistency [15] between the RATA assessment score two by researcher and practitioners.

After practitioners completed assessment using the RTRA, they have completed the RTRA usability questionnaire and provided suggestions for further enhancement and improvement. Suggestions from the ergonomics practitioner were reviewed, the tool was enhanced and refined and become the 3rd prototype as shown in Fig. 3.

Fig. 3

Final prototype of RTRA.

Once the 3rd prototype was completed, the same ergonomics practitioners were invited for retesting and consensus and then RTRA single worksheet was also developed to support when a user wants easy use as it as pen-and-paper-based observational technique [33] as shown in Fig. 4.

Fig. 4

RTRA single worksheet.

3.2.3 RTRA validity test by the practitioners for the final prototype

The same group of the Thai ergonomics practitioners were invited to test the 3rd prototype of the RTRA for consensus after changes per their suggestions. Eight of them participated. Training on how to use the RTRA was given and trial assessment to 3–4 tasks. All practitioners agreed and came to consensus with the 3rd prototype. Then they completed a usability questionnaire, the same one as they did previously but some content in the questionnaire was changed to align with changes of content in the 3rdprototype.

Table 6 explains a total of 20 questions and found only question no. 13 (the tool contained a clear picture of posture) was improved with a significant difference with p-value 0.011.

Table 6
The RTRA usability evaluation by Thai ergonomic practitioners to 2nd and 3rd prototype

Tool usability questionnaire After evaluated 2nd prototype After evaluated 3rd prototype p-value <0.005

3 Totally agree 2 Partially agree 1 Partially disagree 0 Disagree 3 Totally agree 2 Partially agree 1 Partially disagree 0 Disagree

1. The tool is able to identify details of job information 7 (87.5) 1 (12.5) 0(0.0) 0(0.0) 8 (100.0) 0(0.0) 0(0.0) 0(0.0) 0.317

2. The tool is able to identify risk specific on body part (left and right side) 7 (87.5) 1 (12.5) 0(0.0) 0(0.0) 8 (100.0) 0(0.0) 0(0.0) 0(0.0) 0.317

3. The tool is able to identify risk on duration of exposure 7 (87.5) 1 (12.5) 0(0.0) 0(0.0) 7 (87.5) 1 (12.5) 0(0.0) 0(0.0) 1.000

4. The tool is able to identify frequency of exposure “>2.5x/ minute can cause MSD at shoulder” 7 (87.5) 1 (12.5) 0(0.0) 0(0.0) 8 (100.0) 0(0.0) 0(0.0) 0(0.0) 0.317

5. The tool is able to identify risk on physical stress exposure 6 (75.0) 2 (25.0) 0(0.0) 0(0.0) 7 (87.5) 1 (12.5) 0(0.0) 0(0.0) 0.317

6. Work hour > 8 hours 7 (87.5) 1 (12.5) 0(0.0) 0(0.0) 8 (100.0) 0(0.0) 0(0.0) 0(0.0) 0.317

7. WMSD case reported 6 (75.0) 2 (25.0) 0(0.0) 0(0.0) 8 (100.0) 0(0.0) 0(0.0) 0(0.0) 0.157

8. Ergo concerns 7 (87.5) 1 (12.5) 0(0.0) 0(0.0) 7 (87.5) 1 (12.5) 0(0.0) 0(0.0) 1.000

9. Vibration 6 (75.0) 2 (25.0) 0(0.0) 0(0.0) 6 (75.0) 2 (25.0) 0(0.0) 0(0.0) 0.564

10. Cold and hot temperature 6 (75.0) 2 (25.0) 0(0.0) 0(0.0) 5 (62.5) 3 (37.5) 0(0.0) 0(0.0) 0.317

11. Tissue compression 5 (62.5) 3 (37.5) 0(0.0) 0(0.0) 6 (75.0) 2 (25.0) 0(0.0) 0(0.0) 0.564

12. Glove too large or too small 5 (62.5) 3 (37.5) 0(0.0) 0(0.0) 6 (75.0) 2 (25.0) 0(0.0) 0(0.0) 0.564

13.The tool contain a clear picture of posture 1 (12.5) 6 (75.0) 1 (12.5) 0(0.0) 8 (100.0) 0(0.0) 0(0.0) 0(0.0) 0.011

14. The tool is able to identify risk factor on force and load 4 (50.0) 3 (37.5) 1 (12.5) 0(0.0) 8 (100.0) 0(0.0) 0(0.0) 0(0.0) 0.059

15. The tool is able to provide overall risk rating for prioritizing action 4 (50.0) 3 (37.5) 1 (12.5) 0(0.0) 7 (87.5) 1 (12.5) 0(0.0) 0(0.0) 0.102

16. A step-to-step guide to assessment tool ease to understand 6 (75.0) 2 (25.0) 0(0.0) 0(0.0) 5 (62.5) 3 (37.5) 0(0.0) 0(0.0) 0.317

17. Will you use the new assessment tool for repetitive task? 3 (37.5) 5 (62.5) 0(0.0) 0(0.0) 6 (75.0) 2 (25.0) 0(0.0) 0(0.0) 0.083

18. All risk assessment result able to be kept? 6 (75.0) 2 (25.0) 0(0.0) 0(0.0) 7 (87.5) 1 (12.5) 0(0.0) 0(0.0) 0.564

19. The assessment tool is beneficial to use 7 (87.5) 1 (12.5) 0(0.0) 0(0.0) 7 (87.5) 1 (12.5) 0(0.0) 0(0.0) 1.000

20. Will you recommend ergonomics practitioners use this new tool for their further assessment? 6 (75.0) 2 (25.0) 0(0.0) 0(0.0) 7 (87.5) 1 (12.5) 0(0.0) 0(0.0) 0.317

Tool usability questionnaire	After evaluated 2nd prototype	After evaluated 3rd prototype	p-value <0.005
1. The tool is able to identify details of job information	7 (87.5)	1 (12.5)	0(0.0)	0(0.0)	8 (100.0)	0(0.0)	0(0.0)	0(0.0)	0.317
2. The tool is able to identify risk specific on body part (left and right side)	7 (87.5)	1 (12.5)	0(0.0)	0(0.0)	8 (100.0)	0(0.0)	0(0.0)	0(0.0)	0.317
3. The tool is able to identify risk on duration of exposure	7 (87.5)	1 (12.5)	0(0.0)	0(0.0)	7 (87.5)	1 (12.5)	0(0.0)	0(0.0)	1.000
4. The tool is able to identify frequency of exposure “>2.5x/ minute can cause MSD at shoulder”	7 (87.5)	1 (12.5)	0(0.0)	0(0.0)	8 (100.0)	0(0.0)	0(0.0)	0(0.0)	0.317
5. The tool is able to identify risk on physical stress exposure	6 (75.0)	2 (25.0)	0(0.0)	0(0.0)	7 (87.5)	1 (12.5)	0(0.0)	0(0.0)	0.317
6. Work hour > 8 hours	7 (87.5)	1 (12.5)	0(0.0)	0(0.0)	8 (100.0)	0(0.0)	0(0.0)	0(0.0)	0.317
7. WMSD case reported	6 (75.0)	2 (25.0)	0(0.0)	0(0.0)	8 (100.0)	0(0.0)	0(0.0)	0(0.0)	0.157
8. Ergo concerns	7 (87.5)	1 (12.5)	0(0.0)	0(0.0)	7 (87.5)	1 (12.5)	0(0.0)	0(0.0)	1.000
9. Vibration	6 (75.0)	2 (25.0)	0(0.0)	0(0.0)	6 (75.0)	2 (25.0)	0(0.0)	0(0.0)	0.564
10. Cold and hot temperature	6 (75.0)	2 (25.0)	0(0.0)	0(0.0)	5 (62.5)	3 (37.5)	0(0.0)	0(0.0)	0.317
11. Tissue compression	5 (62.5)	3 (37.5)	0(0.0)	0(0.0)	6 (75.0)	2 (25.0)	0(0.0)	0(0.0)	0.564
12. Glove too large or too small	5 (62.5)	3 (37.5)	0(0.0)	0(0.0)	6 (75.0)	2 (25.0)	0(0.0)	0(0.0)	0.564
13.The tool contain a clear picture of posture	1 (12.5)	6 (75.0)	1 (12.5)	0(0.0)	8 (100.0)	0(0.0)	0(0.0)	0(0.0)	0.011
14. The tool is able to identify risk factor on force and load	4 (50.0)	3 (37.5)	1 (12.5)	0(0.0)	8 (100.0)	0(0.0)	0(0.0)	0(0.0)	0.059
15. The tool is able to provide overall risk rating for prioritizing action	4 (50.0)	3 (37.5)	1 (12.5)	0(0.0)	7 (87.5)	1 (12.5)	0(0.0)	0(0.0)	0.102
16. A step-to-step guide to assessment tool ease to understand	6 (75.0)	2 (25.0)	0(0.0)	0(0.0)	5 (62.5)	3 (37.5)	0(0.0)	0(0.0)	0.317
17. Will you use the new assessment tool for repetitive task?	3 (37.5)	5 (62.5)	0(0.0)	0(0.0)	6 (75.0)	2 (25.0)	0(0.0)	0(0.0)	0.083
18. All risk assessment result able to be kept?	6 (75.0)	2 (25.0)	0(0.0)	0(0.0)	7 (87.5)	1 (12.5)	0(0.0)	0(0.0)	0.564
19. The assessment tool is beneficial to use	7 (87.5)	1 (12.5)	0(0.0)	0(0.0)	7 (87.5)	1 (12.5)	0(0.0)	0(0.0)	1.000
20. Will you recommend ergonomics practitioners use this new tool for their further assessment?	6 (75.0)	2 (25.0)	0(0.0)	0(0.0)	7 (87.5)	1 (12.5)	0(0.0)	0(0.0)	0.317

4 Discussion

Most of the assessment tools mainly focus on evaluating external load on biomechanical risk, including posture, frequency, load/ force for specific body part or whole body part, and different work types [46]. Several sources indicated that beside biomechanical factors, psychosocial and work environment ones are among the main cause of the development of MSD [13 , 48]. In comparison with the assessment tool [12], the RTRA can identify risk factors causing MSDs, which included:

Biomechanical: awkward posture, frequency of movement, duration of static posture,

Physical stress (vibration, tissue compression, wearing PPE, work environment (cold temperature)),

Psychosocial risk factor (work hours, concern of worker) that were identified following the scientific literature review. This stage also involves worker providing their identified psychosocial risk factor and opportunity for improvement [49].

The exposure scoring system of each assessment tool is different. The range of exposure data is converted into code, table, or equation. The system provides action level categories which indicate the level of intervention required to reduce the risk of injury. The RTRA was developed based on RULA, the code, table and four action levels are used for Step 2: Risk identification. Physical work environment risk factor and psychosocial risk factor could not be combined as there is still insufficient data to define exactly how exposure to different risk factors should be combined and weighted with respect to their contribution to WRMSD [50]. This study proposed color coding for Step 3: Physical stress and concerns which required investigation and action based on root cause. The RTRA will require further revision and refinement based on its application in the workplace and more sufficient data support.

The RTRA was developed based on RULA and it was classified to Level 3 expertise [9] that the tool is much more complex, takes longer to use and mostly requires videotaping and specific skills in methodology. It means the RTRA user should be trained in basic ergonomic knowledge to understand causes of MSD, how to use the tool and intervention to reduce risk. The training also can reduce analysis time associated with video-based posture assessment methods and making these type of approaches feasible for larger-scale field studies [51].

The first phase of the study was to test the usability and validity of RTRA. A panel of seven international experts/ professional with knowledge of similar assessment tools assessed with the review and development [11, 52], found the IOC over than 0.5 of all questions, which means the panelists confirmed that RTRA can be used to assess repetitive task.

At the second phase, the intra-rater and inter-rater evaluation was conducted by researcher twice at an interval of 4 weeks. Thirty tasks and nine practitioners assess the same set of tasks. An overall intra-observer reliability was good to excellent 0.932 (95% CI: 0.862–0.967) and inter-observer reliability was 0.95 (95% CI: 0.90–0.97) respectively [11 , 52–55] which demonstrated that the RTRA is valid to use to assess repetitive tasks.

In comparison between intra-observer and inter-observer reliability, the consistency of assessment results of inter-rater was higher than intra-observer because of researcher was more familiar with the tool in conducting inter-rater reliability.

Number of observers, most studies use only one or two observers, however more information use several observers [56] and there was evidence suggests that a consensus group estimate by multiple ergonomics assessor, or an average of their estimates, improves posture assessment [36]. When multiple assessors estimate or rate posture severity, the average of these ratings is likely to be more accurate than most individual ratings, but this approach is more time and resource intensive because of the need for multiple observers, and it will decrease the speed of the posture assessment method. It may be feasible in a research application, but it may be less practical in an industrial application. This study used nine practioners from multiple sectors performing assessment together which allowed them discussion and consensus risk rating more accuracy and they could complete thirty tasks in one day.

Discrepancies, 12.5% of intra-rater reliability, and 10% of inter-rater reliability occurred when a body segment posture was at a border between 2 ranges, usually when assessing the lower arm and wrist posture [11, 57]. A critical angle of 15° showed that observers had difficulty in distinguishing between wrist posture below and above this angle.

Other investigators have confirmed that approximately 30% of assessment performed by practitioners had errors [58], it is not possible to estimate wrist angle very precisely in the workplace [59]. However, the Kinovea program could be helpful to identify the actual angle, before rating the score in the RTRA if users need to get a more accurate evaluation result. However, this tool can evaluate only the angle of posture, and frequency but does not cover all needs from the repetitive work, such as load and force which need measurement equipment.

The RTRA validity test found only one area on picture of posture was improved with a significant difference while other areas were not required improvement. The improving posture picture by adding border, shading and color to the posture categories effect on posture selection error rates and decision times of novice analyst [60].

With a clear and precise given job information on work hours, concerns of employees, WRMSD case reported, vibration, cold temperature and wearing PPE, lead both researcher and practitioner rating ergonomics risk score are entirely consistent.

The certain limitations were present throughout the study. The major limitations included obtaining a permit from a manufacturing company regarding proprietary information policy for collecting 30 repetitive job descriptions, taking videos and interviewing participants. Furthermore, timing constrainst of the national practitioners to do assessment together in one day with long hours together with group gathering during the COVID-19 pandemic was not encouraged.

5 Conclusion

The study’s goal was to review the observational ergonomics risk assessment tools which are frequently used in industry to identify potential areas for improvement. The review’s findings with input from an international ergonomics professional experts and practitioners was then used to modify and improve observational ergonomics risk assessment tool for repetitive tasks.

Validity tests by ergonomics panel and intra and inter-rater reliability test confirmed that the RTRA is a systematic assessment tool able to identify most risk factors which cause MSD for repetitive tasks, prioritize risk to further take corrective action and systematically record all risk assessment results.

More strengths and weakness of RTRA found in the study are:

RTRA can be widely used and will help users in record keeping and allows for risk prioritization and ongoing reviews.

RTRA assessment efficiency is beneficial, especially for manufacturing where hundreds to thousands of tasks are spread across a large location.

RTRA assessments can be performed in both a worksheet format and using a computerized system.

RTRA computerized system was developed to automatically calculate risk ratings, which provides uniformity, standardized an accurate calculation, and time efficiencies.

RTRA’s computerized system automates risk exposure level and rating is filed and easily retrieved for ongoing work and future reviews, to compare with other tasks and locations across a global company’s sites.

Training material and step-by-step guidance allowed new RTRA users to learn and undertake ergonomics assessment process and refresher training.

Using RTRA will provide users with ergonomics knowledge and will allow them to build on their experience and knowledge.

The RTRA tool (with worker’s collaboration) will improve and provide the employees with ownership and knowledge of the organization’s ergonomics challenges and potential solutions. Video recorder (camera or mobile phone) is a critical resource.

The RTRA was developed by using a Microsoft operating system required a Net Framework 4.0 or above to operate. This requirement limited the user who did not use Microsoft PC operating system.

There is a suggestion for researchers to understand more on the identification of multiple risk factors in one assessment tool and consider a risk-level rating and scoring to prioritize risk reduction.

Footnotes

Acknowledgments

This study has been made possible with the support of Dr. Lynn McAtamney (RULA owner), seven ergonomics experts from Australia, Singapore, Switzerland, Thailand and USA for review and advice on the new tool design and two engineers from HDD Company for help with the drawing and design of the worksheet assessment tool. Their kind support is gratefully acknowledged.

Funding

This study was supported by Thammasat University Research Fund for Graduate Students, Contract No. 8/2562, Fiscal Year 2019.

Ethics statement

This study was approved by the Ethics Review Sub-Committee of Thammasat University (Project code 199/2560).

Informed consent

Not applicable.

Conflict of interest

Not applicable.

Supplementary materials

The appendices are available from .

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