From Motion to Prevention: Evaluating Ergonomic Risks of Asymmetrical Movements and Worker Well-Being in an Assembly Line Work

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This work investigates the association between asymmetrical movements of assembly line and machining workers and their overall well-being. The idea and implementation of Motion Activity Index to measure movement intensity, asymmetry, and quality are novel, however, this work can improve in certain directions in order to achieve this study in a practical way. The manuscript has an impact on industries, however I have the following concerns and would like to receive answers from the authors.

  - The intricate details of the movements outlined in this document have not been revealed.

 - In the second section, does the motion state described vary among workers? How is personal variability ascertained?

 - Has a comparative analysis been performed in the research assessing workers' conditions, examining their state before and after the work?

 - The research highlights the tracking of the researchers' state for 30 minutes; does this mean that the workers' years of experience are outside the realm of consideration?

 - The authors have tracked assessments that occur triennially; do these evaluations evolve over time? Is there significant employee turnover within the experimental workforce?

  - Do the key motion patterns of assembly workers align with the measured data?

 - The annex materials are inaccessible; it is recommended to include photographs or videos of the workers' movements in the annex to validate the accuracy of the measurement data.

Author Response

This work investigates the association between asymmetrical movements of assembly line and machining workers and their overall well-being. The idea and implementation of Motion Activity Index to measure movement intensity, asymmetry, and quality are novel, however, this work can improve in certain directions in order to achieve this study in a practical way. The manuscript has an impact on industries, however I have the following concerns and would like to receive answers from the authors.

  - The intricate details of the movements outlined in this document have not been revealed.

• We appreciate the reviewer’s thoughtful feedback and the opportunity to address the concern raised regarding the intricate details of the movements examined in our study.
• To clarify, the movements analysed in the study are comprehensively described in the Methods section of the manuscript. To ensure absolute clarity and address the reviewer’s concerns, we have further elaborated on the descriptions of the intricate movement patterns in the revised manuscript. Now the section reads: “The current study systematically examined a series of standardised machining tasks. These tasks comprised the following steps: (1) lifting four components simultaneously—three with one hand and one with the other—from a metal container; (2) clearing metal chips from the clamping base; (3) securing components onto the clamping device; (4) performing the deburring process; (5) transferring the components to an engraving machine to initiate the marking cycle; (6) conducting a visual inspection to ensure task accuracy; and (7) placing the components onto a hanger. The manipulation processes were primarily unilateral, with the left limb performing active manipulative actions while the right limb played a stabilising and supportive role. Each component weighed approximately 520 grams before the operation and 380 grams after processing. These standardised tasks facilitated accurate motion capture using inertial sensors, allowing for detailed analysis of angular displacements, velocities, and asymmetries in the thoracic and lumbar regions. The experimental setup also included a series of standardised assembly tasks, specifically focusing on constructing the spring-piston unit. The task sequence consisted of the following steps: (1) retrieving the spring with the left hand from its designated container; (2) picking up the piston with the right hand from the corresponding piston box; (3) positioning the spring pack vertically within the centring sleeve; (4) placing the piston on top of the spring pack; (5) performing a visual inspection to verify the accuracy of the operation; and (6) transferring the completed spring-piston unit to the next assembly point. The weights of the components used in this process ranged between 100 and 400 grams.”

 - In the second section, does the motion state described vary among workers? How is personal variability ascertained?

• We have included an analysis of personal variability in the revised manuscript. Specifically, we calculated the interquartile range (IQR = Q3 − Q1) to quantify variability. This measure captures both within-subject and between-subject variability in the assessed movements.

 - Has a comparative analysis been performed in the research assessing workers' conditions, examining their state before and after the work?

• No, all measurements were taken during the work shift. Although the measurements were conducted only once, the GHQ questionnaire evaluates general psychophysiological states related to well-being experienced over the previous weeks. According to the instructions for this tool, the currently experienced mood does not significantly affect the reliability of the results. This clarification has been incorporated into the revised manuscript in the Methods.

 - The research highlights the tracking of the researchers' state for 30 minutes; does this mean that the workers' years of experience are outside the realm of consideration?

• Participants were required to have a minimum of six months of experience at their respective workstations to ensure familiarity with the tasks. Additionally, an age cap of 60 years was implemented to minimise variability due to age-related factors. However, differences in professional experience were not considered in the analysis of results.

 - The authors have tracked assessments that occur triennially; do these evaluations evolve over time? Is there significant employee turnover within the experimental workforce?

• The assessment conducted before the study focused solely on ergonomic measurement. We did not explore the relationship with employee turnover. According to the documentation, there were mild ergonomic improvements each year based on the company's established norms. Moreover, these evaluations are regularly updated to reflect advancements in ergonomic standards, technological improvements, and feedback from previous evaluations. Importantly, the systematically conducted (company internal) risk assessments (“ergo checks”) consistently indicate that the level of risk remains stable and within acceptable limits.

  - Do the key motion patterns of assembly workers align with the measured data?

• Yes, the key patterns of both MWE and AWE workers, as described in the Methods section, align with the measured data.

 - The annex materials are inaccessible; it is recommended to include photographs or videos of the workers' movements in the annex to validate the accuracy of the measurement data.

• Unfortunately, we did not have permission from the company’s management to record or publish any data, including photographs or videos, that could potentially identify the company or its manufacturing processes. For this reason, we could only include a schematic representation in Figure 1, which depicts the experimental setup. We hope that the detailed description of the workers’ movements provided in the Methods section will be sufficient to validate the accuracy of the data.
• Once again, we appreciate the reviewer’s thoughtful feedback, and we hope that our clarifications and revisions adequately address the reviewer’s concerns. We remain open to any further suggestions that could help improve the quality and clarity of our work.

Reviewer 2 Report

Comments and Suggestions for Authors

No comments.

Comments for author File: Comments.pdf

Author Response

No attached comments. Response to comments in the PDF file.

• We appreciate the reviewer’s thoughtful feedback. We had some problems with reading or understanding all the comments, but realised that the reviewer raised concerns about autoplagiarism of our work. The similarity with the preprint has been explained, and we got a response from the editor, Eden Ma, that there is no need to withdraw the preprint from the service. We also resolved the "similarity check" issue with our former work titled "Added value of motion capture technology for occupational health and safety innovations" and removed all the repetitions (mostly in the description of methods) or used paraphrases.
• Nevertheless, we found some useful tips in the PDF File that we could use in the revised version.
• The typos, the reviewer commented on were due to the difference between American and British English. We tried to keep consistency in the text and used BE because we are from Europe.
• Based on the reviewer’s comments, we have also revised the last paragraphs of the discussion, providing subsections: “4.1. Study limitations and areas for improvement” and “4.2. Future directions and research implications”, for better clarifications.
• Again, we appreciate the reviewer’s thoughtful feedback, and we hope that our clarifications and revisions adequately address the reviewer’s concerns. We remain open to any further suggestions that could help improve the quality and clarity of our work.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

thank you for the opportunity to review the manuscript. Some comments/suggestions given below:

1. If you state that groups differed with age, body mass, height it is sampling bias. Please provide the results of the groups comparison. Moreover, please specify the work experience (range + standard deviation).

2. It is not clear what exclusion criteria were set if authors write “A crucial health-related criterion was the 161 absence of any history of musculoskeletal system pain that could potentially affect their 162 range or speed of movement”. Please specify “musculoskeletal system pain”.  Everyone experienced musculoskeletal pain, in particular if mean age of the participants was above 30.

3. I think you should look for some correlations between movements and General GHQ. Otherwise, this study will be little informative and it will be difficult to conclude about the workers’ health status.

Author Response

Dear Authors,

thank you for the opportunity to review the manuscript. Some comments/suggestions given below:

1. If you state that groups differed with age, body mass, height it is sampling bias. Please provide the results of the groups comparison. Moreover, please specify the work experience (range + standard deviation).

• We appreciate the reviewer’s request for clarification. We have provided a table of comparative summary of demographic characteristics, including age, body mass, height, and work experience, in the form of a table (now Table 1). Additionally, we conducted statistical tests to compare the groups. The analysis did not reveal significant differences between the groups in demographic characteristics (p > 0.05). However, there was notable diversity in the range of employment duration, spanning from 0.5 to 40 years.

2. It is not clear what exclusion criteria were set if authors write “A crucial health-related criterion was the 161 absence of any history of musculoskeletal system pain that could potentially affect their 162 range or speed of movement”. Please specify “musculoskeletal system pain”.  Everyone experienced musculoskeletal pain, in particular if mean age of the participants was above 30.

• To clarify, we have refined the description to specify the type of musculoskeletal pain considered for exclusion. Now the section reads: An important health-related exclusion criterion was the absence of clinically diagnosed chronic or recurring musculoskeletal pain that might influence the participant's range or speed of movement, such as chronic lower back pain, joint pain associated with osteoarthritis, or ongoing pain resulting from prior musculoskeletal injuries. Mild or temporary musculoskeletal discomfort was not grounds for exclusion.

3. I think you should look for some correlations between movements and General GHQ. Otherwise, this study will be little informative and it will be difficult to conclude about the workers’ health status.

• We did attempt to conduct such correlations; however, several methodological challenges arose from the nature of the data. The GHQ relies on subjective psychological assessments based on population norms, while the movement data consists of individual-specific, objective physical measurements. This discrepancy required correlating mean standardised GHQ scores with raw motion data, which introduced artefacts and rendered the results unreliable. Additionally, the GHQ assesses general health states over the preceding weeks, whereas the Myomotion system captures instantaneous physical measurements. Due to these fundamental differences in data types and time scales, correlating the two proved methodologically inappropriate.
• Once again, we appreciate the reviewer’s thoughtful feedback, and we hope that our clarifications and revisions adequately address the reviewer’s concerns. We remain open to any further suggestions that could help improve the quality and clarity of our work.

 

Reviewer 4 Report

Comments and Suggestions for Authors

This manuscript explores the impact of asymmetrical movements during work on the health of assembly line and machining workers, with a particular focus on the predictive role of such movements in work-related musculoskeletal disorders (WMSDs). Impressively, by utilizing inertial motion capture technology and health questionnaires, the study reveals substantial differences in joint angle displacement, velocity, and acceleration between machining and assembly workers. The findings highlight the importance of specific ergonomic interventions to enhance workers' health and advocate for preventive health measures in occupational settings. The manuscript is suitable for publication following minor revisions.

1. Whether the use of the Motion Activity Index (MAI) effectively reflects workers’ health status and how MAI assists in identifying potential health risks should be clarified.

2. The authors should discuss what methods are most effective in reducing movement asymmetry and how these can be practically implemented in real work environments to lower the incidence of injuries and health issues.

3. The study should address whether significant differences in movement asymmetry were found between assembly line workers and machining workers and how these differences influence their work performance and injury risks.

4. It is important to clarify whether workers with higher movement asymmetry exhibit lower work efficiency or higher levels of work-related fatigue.

Author Response

This manuscript explores the impact of asymmetrical movements during work on the health of assembly line and machining workers, with a particular focus on the predictive role of such movements in work-related musculoskeletal disorders (WMSDs). Impressively, by utilizing inertial motion capture technology and health questionnaires, the study reveals substantial differences in joint angle displacement, velocity, and acceleration between machining and assembly workers. The findings highlight the importance of specific ergonomic interventions to enhance workers' health and advocate for preventive health measures in occupational settings. The manuscript is suitable for publication following minor revisions.

1. Whether the use of the Motion Activity Index (MAI) effectively reflects workers’ health status and how MAI assists in identifying potential health risks should be clarified.

• We appreciate the reviewer’s request for clarification. The MAI was designed to quantify the intensity and activity of workers’ movements as a standardised, one-dimensional index based on preselected variables, including range of motion, velocities, and accelerations. By objectively assessing movement patterns, the MAI effectively highlights asymmetries or deviations from optimal, symmetrical profiles, which, according to existing ergonomic literature, are associated with an increased risk of musculoskeletal disorders (MSDs). While the MAI does not directly measure health outcomes such as pain or fatigue, it provides critical insights into movement dynamics that act as early indicators of potential health risks. For instance, a higher asymmetry score or constrained movement may signal uneven physical strain, which, if unaddressed, could lead to overuse injuries or long-term MSDs. These findings can be used as early-warning signals, prompting ergonomic interventions before significant health issues develop. To clarify its utility, we have revised the manuscript (in subsection 2.7) with the proposed explanation: “While the MAI does not directly measure health outcomes, it may offer valuable insights into movement dynamics. These dynamics are crucial for identifying potential health risks linked to asymmetrical, repetitive movements, which are known precursors to musculoskeletal disorders. MAI can help guide targeted ergonomic interventions to address these identified risks before health complications arise.”

1. The authors should discuss what methods are most effective in reducing movement asymmetry and how these can be practically implemented in real work environments to lower the incidence of injuries and health issues.

• While the primary focus of this study was to identify and quantify movement asymmetry, we acknowledge the importance of discussing practical methods for reducing asymmetries. We proposed a revised text in the Discussion: To address the identified movement asymmetries, practical solutions such as ergo-nomic workstation redesign, task rotation, physical conditioning programs, and assistive technologies could be implemented [48]. These methods are well-documented in the ergonomic literature as effective strategies for reducing movement asymmetry and preventing musculoskeletal disorders in occupational settings. We listed some methods described by the authors: [48.] Odebiyi, D.O.; Okafor, U.A.C.; Odebiyi, D.O.; Okafor, U.A.C. Musculoskeletal Disorders, Workplace Ergonomics and Injury Prevention. Ergonomics - New Insights 2023, doi:10.5772/INTECHOPEN.106031

1. The study should address whether significant differences in movement asymmetry were found between assembly line workers and machining workers and how these differences influence their work performance and injury risks.

• Our research clearly demonstrates significant differences in movement asymmetry between assembly line workers and machining workers as described in the results and widely discussed. Machining workers displayed predominantly symmetrical movement patterns, with only a slight tendency towards increased activity on the right side. In contrast, assembly line workers exhibited more pronounced asymmetrical movements and significantly higher activity levels on the right side. Based on existing literature, such asymmetries are known to influence work performance and injury risks, as they can lead to increased strain on specific muscle groups, resulting in fatigue or overuse injuries. However, the detailed assessment of how these asymmetries impact performance and injury risk was beyond the scope of the current study.

1. It is important to clarify whether workers with higher movement asymmetry exhibit lower work efficiency or higher levels of work-related fatigue.

• While our study highlights differences in movement asymmetry between assembly line workers and machining workers, it did not directly assess work efficiency or fatigue levels in relation to asymmetry. However, our findings indicate that the repetitive motions and asymmetrical body positions common in manufacturing tasks negatively impact physical health, contributing to fatigue and exhaustion. Notably, approximately 74% of participants scored higher than the average value of a "healthy sample" on the General Health Questionnaire, reflecting significant somatic concerns such as frequent exhaustion, weakness, tiredness, and bodily pain. The revised text in the Discussion section: Although the study did not directly evaluate the relationship between movement asymmetry and work efficiency or fatigue, the findings suggest that repetitive, asymmetrical tasks negatively influence physical health. Approximately 74% of participants reported somatic complaints, including exhaustion, weakness, and bodily pain (Table 6), which may be linked to the physical demands of their roles.
• Once again, we appreciate the reviewer’s thoughtful feedback, and we hope that our clarifications and revisions adequately address the reviewer’s concerns. We remain open to any further suggestions that could help improve the quality and clarity of our work.

Reviewer 5 Report

Comments and Suggestions for Authors

This paper emphasizes to find the relationship between asymmetrical movement in the workplace and health outcome of workers. Specifically, this study explores the connection between asymmetrical movements in assembly line and machining workers and their overall well-being. 

Results of this research may be significative to providing guiding opinions for workplace ergonomics and preventing health issues related with the workplace.

The work is properly organized and described, and the data of experiments is convictive. 

1. Whether improvements of workplace ergonomics can be made based on the conclusion obtained from the investigation？

2. Will the measurement error introduced by the activities of worker and measurement instruments during the operations affect the final conclusion？

 

Author Response

This paper emphasizes to find the relationship between asymmetrical movement in the workplace and health outcome of workers. Specifically, this study explores the connection between asymmetrical movements in assembly line and machining workers and their overall well-being. 

Results of this research may be significative to providing guiding opinions for workplace ergonomics and preventing health issues related with the workplace.

The work is properly organized and described, and the data of experiments is convictive. 

1. Whether improvements of workplace ergonomics can be made based on the conclusion obtained from the investigation？

• We appreciate the reviewer’s request for clarification. We firmly believe that workplace ergonomics can be improved based on the conclusions obtained from our study. While the primary aim was to identify movement asymmetries and their associated risks, the results clearly highlight distinct ergonomic risk profiles for machining workers (MWE) and assembly line workers (AWE). This provides a strong basis for designing targeted ergonomic interventions. In the article, we have provided several recommendations for designers of such interventions, emphasising the promotion of symmetrical movement patterns in workplace design and the need for customised approaches that address the unique physical requirements of various types of work.

2. Will the measurement error introduced by the activities of worker and measurement instruments during the operations affect the final conclusion？

• While minor measurement errors may occur due to worker activities and instrument limitations (Listed in the limitations of the study at the end of Discussion), we ensured their impact on the final conclusions was minimal. We also included IQR The use of inertial motion capture technology, which is validated for accuracy in occupational settings, allowed us to reliably measure movement parameters such as range of motion, velocities, and accelerations. Additionally, the standardised work tasks and controlled data collection procedures reduced variability and consistency across participants. We calculated the interquartile range (IQR) in the collected movement data to further assess measurement repeatability and variability.
• Once again, we appreciate the reviewer’s thoughtful feedback, and we hope that our clarifications and revisions adequately address the reviewer’s concerns. We remain open to any further suggestions that could help improve the quality and clarity of our work.

 

 

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

the manuscript has been improved in a deep way.

Thank you.

Author Response

Thank you once again for your time.

The Authors