Effects of Sensor Types and Angular Velocity Computational Methods in Field Measurements of Occupational Upper Arm and Trunk Postures and Movements (original) (raw)
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IEEE Access, 2021
The Rapid Upper Limb Assessment (RULA) is frequently used to monitor body posture for early risk prevention of work-related musculoskeletal disorders. However, RULA measurements that are based on workers' self-report or external rater observation suffer from low repeatability. Thus, the objective of this study was to investigate the accuracy and repeatability of an inertial measurement unit (IMU) system for in-field RULA score assessment during manual material handling tasks using 3D Cardan angles and 2D projection angles against reference values obtained by a motion-capture camera system. The experimental results showed that for trunk and neck joint angles, the 2D convention had significantly (p<0.05) smaller root-mean-square error (RMSE), while for other upper-body angles, the convention with significantly smaller RMSE depended on the angle under analysis. Also, the 3D convention showed a ''moderate'' agreement with the reference system, while the 2D convention showed a ''substantial'' agreement for two tasks and a ''moderate'' agreement for one task. Moreover, the intraclass correlation coefficients ranged from 0.82 to 0.94 for the 3D convention and 0.87 to 0.95 for the 2D convention for repeated trials performed by each participant. Therefore, the wearable IMU system, along with the 2D convention, could be considered as an accurate and repeatable ergonomic risk assessment tool. INDEX TERMS Ergonomic risk assessment, inertial measurement unit, material handling tasks, RULA, work-related musculoskeletal disorders.
Scandinavian Journal of Work, Environment & Health, 2014
This study is the first to carry out comprehensive cost-efficiency comparisons of ergonomic exposure assessment, providing quantitative rationale for the development of a hierarchy of exposure assessment methods. Combined with the accompanying model for assessing cost-efficiency, the empirical data provides a basis for planning posture assessment and allows for informed use of limited resources when designing ergonomic studies. Trask C, Mathiassen SE, Walhström J, Forsman M. Cost-efficient assessment of biomechanical exposure in occupational groups, exemplified by posture observation and inclinometry. Scand J Work Environ Health.
Explaining the Ergonomic Assessment of Human Movement in Industrial Contexts
Proceedings of the 13th International Joint Conference on Biomedical Engineering Systems and Technologies, 2020
Manufacturing processes are based on human labour and the symbiosis between human operators and machines. The operators are required to follow predefined sequences of movements. The operations carried out at assembly lines are repetitive, being identified as a risk factor for the onset of musculoskeletal disorders. Ergonomics plays a big role in preventing occupational diseases. Ergonomic risk scores measure the overall risk exposure of operators however these methods still present challenges: the scores are often associated to a given workstation, being agnostic to the variability among operators. Observation methods are most often employed yet require a significant amount of effort, preventing an accurate and continuous ergonomic evaluation to the entire population of operators. Finally, the risk's results are rendered as index scores, hindering a more comprehensive interpretation by occupational physicians. This dissertation developed a solution for automatic operator risk exposure in assembly lines. Three main contributions were presented: (1) an upper limb and torso motion tracking algorithm which relies on inertial sensors to estimate the orientation of anatomical joints; (2) an adjusted ergonomic risk score; (3) an ergonomic risk explanation approach based on the analysis of the angular risk factors. Throughout the research, two experimental assessments were conducted: laboratory validation and field evaluation. The laboratory tests enabled the creation of a movements' dataset and used an optical motion capture system as reference. The field evaluation dataset was acquired on an automotive assembly line and serve as the basis for an ergonomic risk evaluation study. The experimental results revealed that the proposed solution has the potential to be applied in a real environment. Through direct measures, the ergonomic feedback is fastened, and consequently, the evaluation can be extended to more operators, ultimately preventing, in long-term, work-related injuries.
2020
Work-related upper extremity musculoskeletal disorders (WRUED) are a major problem in modern societies as they affect the quality of life of workers and lead to absenteeism and productivity loss. According to studies performed in North America and Western Europe, their prevalence has increased in the last few decades. This challenge calls for improvements in prevention methods. One avenue is through the development of wearable sensor systems to analyze worker's movements and provide feedback to workers and/or clinicians. Such systems could decrease the physical work demands and ultimately prevent musculoskeletal disorders. This paper presents the development and validation of a data fusion algorithm for inertial measurement units to analyze worker's arm elevation. The algorithm was implemented on two commercial sensor systems (Actigraph GT9X and LSM9DS1) and results were compared with the data fusion results from a validated commercial sensor (XSens MVN system). Cross-correl...
Annals of work exposures and health, 2018
Regarding prevention of neck and shoulder pain (NSP), unsupported arm elevation is one factor that should be taken into account when performing work risk assessment. Triaxial accelerometers can be used to measure arm elevation over several days but it is not possible to differentiate between supported and unsupported arm elevation from accelerometers only. Supported arm elevation is more likely to exist during sitting than standing. The aim of the study was to evaluate the use of whole workday measurements of arm elevation with accelerometers to assess potentially harmful work exposure of arm elevation, by comparing arm elevation at work with arm elevation during leisure, in a population with diverse work tasks, and to assess how the exposure parameters were modified when upper arm elevation during sitting time was excluded. The participants, 197 workers belonging to 12 occupational groups with diverse work tasks, wore triaxial accelerometers on the dominant arm, hip, and back for 1...
Journal of Engineering Science and Technology Review
Poor wrist postures due to work requirements is one of the established risk factors contributing to the development of workrelated musculoskeletal disorders. This study systematically investigates the underlying hypothesis that identification and monitoring of poor wrist postures at work should be in the function of normalized wrist range-of-motion (ROM) instead of the traditional measurement of absolute wrist angle. This three-stage study looks into 1) existing issues related to current workplace wrist postural assessment methods, 2) development of a new architecture to assess and monitor wrist posture at work, and 3) qualitative review with ergonomics practitioners on the architecture. The first stage utilizes literature review and interview with ergonomics practitioners. Generative collaboration method was used to generate the architecture for the second stage. The third stage employs semi-structured interview with ergonomics practitioners. Several issues were identified in current wrist postural assessment methods. A conceptual architecture of the Wrist ROM System to assess and monitor wrist postural behaviors at workplace is proposed in this manuscript. The architecture was generally well received by the practitioners. The architecture provides the groundwork in the development of a technological system designed as a tool to analyze workplace wrist postural behaviors.
Accuracy and validity of observational estimates of shoulder and elbow posture
Applied Ergonomics, 2004
This study investigated the accuracy of video-based observational posture analysis for the elbow and shoulder. Posture analyses were conducted by 28 ergonomists for four jobs presented on a traditional VHS format video recording. Estimates of posture from the observational-based methods were compared with values measured directly with an optical motion capture system. Ergonomists used categorical posture scales and a continuous visual analog scale to estimate the peak and most frequently occurring or average posture for each job. Use of a three-category scale resulted in misclassifications of peak and most frequently occurring elbow and shoulder posture with a probability averaging 30.1%. With the six-category posture scale this average probability of misclassification increased to 64.9%. Using a continuous visual analog scale peak shoulder elevation was the only posture for which the average error among ergonomists' estimates was significantly different from zero ðpo0:05Þ: Correlations between the estimated postures and measured postures were higher and statistically significant ðpo0:05Þ for elbow flexion and shoulder elevation (r 2 between 0.45 and 0.66) but were considerably lower and not significant (r 2 between 0.03 and 0.18) for the peak and average horizontal shoulder abduction. Ergonomists' estimates of the temporal distribution of shoulder posture, indicating the duration severity of the posture, appeared to be biased such that the percentage of the cycle time in each posture category was estimated as more uniformly distributed than the measured values indicated.
Evaluation of interrater reliability for posture observations in a field study
Applied Ergonomics, 1999
This paper examines the interrater reliability of a quantitative observational method of assessing non-neutral postures required by work tasks. Two observers independently evaluated 70 jobs in an automotive manufacturing facility, using a procedure that included observations of 18 postures of the upper extremities and back. Interrater reliability was evaluated using percent agreement, kappa, intraclass correlation coefficients and generalized linear mixed modeling. Interrater agreement ranged from 26% for right shoulder elevation to 99 for left wrist flexion, but agreement was at best moderate when using kappa. Percent agreement is an inadequate measure, because it does not account for chance, and can lead to inflated measures of reliability. The use of more appropriate statistical methods may lead to greater insight into sources of variability in reliability and validity studies and may help to develop more effective ergonomic exposure assessment methods. Interrater reliability was acceptable for some of the postural observations in this study.
Sensors, 2019
Background: Workplace adaptation is the preferred method of intervention to diminish risk factors associated with the development of work-related shoulder disorders. However, the majority of the workplace assessments performed are subjective (e.g., questionnaires). Quantitative assessments are required to support workplace adaptations. The aims of this study are to assess the concurrent validity of inertial measurement units (IMUs; MVN, Xsens) in comparison to a motion capture system (Vicon) during lifting tasks, and establish the discriminative validity of a wireless electromyography (EMG) system for the evaluation of muscle activity. Methods: Sixteen participants performed 12 simple tasks (shoulder flexion, abduction, scaption) and 16 complex lifting tasks (lifting crates of different weights at different heights). A Delsys Trigno EMG system was used to record anterior and middle deltoids’ EMG activity, while the Xsens and Vicon simultaneously recorded shoulder kinematics. Results...