Capability of Machine Learning Algorithms to Classify Safe and Unsafe Postures during Weight Lifting Tasks Using Inertial Sensors.

Occupational ergonomics aims to optimize the work environment and to enhance both productivity and worker well-being. Work-related exposure assessment, such as lifting loads, is a crucial aspect of this discipline, as it involves the evaluation of physical stressors and their impact on workers' health and safety, in order to prevent the development of musculoskeletal pathologies. In this study, we explore the feasibility of machine learning (ML) algorithms, fed with time- and frequency-domain features extracted from inertial signals (linear acceleration and angular velocity), to automatically and accurately discriminate safe and unsafe postures during weight lifting tasks. The signals were acquired by means of one inertial measurement unit (IMU) placed on the sternums of 15 subjects, and subsequently segmented to extract several time- and frequency-domain features. A supervised dataset, including the extracted features, was used to feed several ML models and to assess their prediction power. Interesting results in terms of evaluation metrics for a binary safe/unsafe posture classification were obtained with the logistic regression algorithm, which outperformed the others, with accuracy and area under the receiver operating characteristic curve values of up to 96% and 99%, respectively. This result indicates the feasibility of the proposed methodology-based on a single inertial sensor and artificial intelligence-to discriminate safe/unsafe postures associated with load lifting activities. Future investigation in a wider study population and using additional lifting scenarios could confirm the potentiality of the proposed methodology, supporting its applicability in the occupational ergonomics field.

Biomechanical Effects of Using a Passive Exoskeleton for the Upper Limb in Industrial Manufacturing Activities: A Pilot Study.

This study investigates the biomechanical impact of a passive Arm-Support Exoskeleton (ASE) on workers in wool textile processing. Eight workers, equipped with surface electrodes for electromyography (EMG) recording, performed three industrial tasks, with and without the exoskeleton. All tasks were performed in an upright stance involving repetitive upper limbs actions and overhead work, each presenting different physical demands in terms of cycle duration, load handling and percentage of cycle time with shoulder flexion over 80°. The use of ASE consistently lowered muscle activity in the anterior and medial deltoid compared to the free condition (reduction in signal Root Mean Square (RMS) -21.6% and -13.6%, respectively), while no difference was found for the Erector Spinae Longissimus (ESL) muscle. All workers reported complete satisfaction with the ASE effectiveness as rated on Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST), and 62% of the subjects rated the usability score as very high (>80 System Usability Scale (SUS)). The reduction in shoulder flexor muscle activity during the performance of industrial tasks is not correlated to the level of ergonomic risk involved. This preliminary study affirms the potential adoption of ASE as support for repetitive activities in wool textile processing, emphasizing its efficacy in reducing shoulder muscle activity. Positive worker acceptance and intention to use ASE supports its broader adoption as a preventive tool in the occupational sector.

Evaluation of orderliness of underground workplace system based on occupational ergonomics: A case study in Guangzhou and Chengdu metro depots.

BACKGROUND: An underground workplace (UGW) is a complex system with multiple subsystems that interact with each other. However, the research on UGW from a systemic perspective has not received due attention. OBJECTIVE: This study constructs an evaluation approach to the orderliness of UGW and systematically evaluates the UGW with Guangzhou and Chengdu metro depots as case studies. METHODS: First, the evaluation index system is established based on occupational ergonomics. Second, the system entropy model is constructed based on information entropy. Third, a dissipative structure judgment model is built based on the Brusselator. Fourth, the orderliness evaluation model is constructed based on information entropy and synergetics. RESULTS: The UGW of the metro depot has not yet reached the dissipative structure and is in a medium-order state. But the system is in the trend of orderly development. The entropy increase caused by the physical environment and health status is the main obstacle for the system to move toward order. The equipment configuration is an essential source of system negative entropy. The coordination between equipment configuration, health status, and physical environment is low, and that of work effectiveness, equipment aging and failure, and organizational environment is high. CONCLUSIONS: Equipment configuration cannot fully cope with the harsh physical environment and meet the needs of underground workers. Safety security equipment has more room for improvement. Humanized support facilities can introduce more negative entropy to the system. Organizational intervention can reduce the negative impact of adverse factors on the system.

An ergonomic focus evaluation of work-related musculoskeletal disorders amongst operators in the UAE network control centres.

Work-related musculoskeletal disorders (WMSDs) have rapidly increased during the last decade, but only a few descriptive surveys have been conducted in the United Arab Emirates (UAE). This study investigated the prevalence of WMSDs and analysed their ergonomic risks amongst operators in the network control rooms across two government organisations, X and Y, in the UAE. Essential data were collected by the Nordic Musculoskeletal Questionnaire (NMQ) and the Maastricht Upper Extremity Questionnaire (MUEQ) from online surveys and direct observations based on the Rapid Office Strain Assessment (ROSA) and the Rapid Upper Limb Assessment (RULA) form and ergonomic measurements for the working environments, respectively. Fifty-three and eighteen operators participated from Organisations X and Y. This study found a high presence of WMSDs in both organisations over the past 12 months. In Organisation X, individual, work-related physical and psychosocial risk factors of high BMI, educational level, morning work shift, high job duration, lack of exercise habit, awkward body posture, high job demand, low job control, and low work social support were associated with WMSDs in different body areas (p < 0.05). In Organisation Y, older age, high BMI, high job duration, lack of exercise habits, unergonomic workstations, awkward body posture, low break time, high job demand, and stress level were associated with WMSDs in different body areas (p < 0.05). The control room operators' most affected body areas were the back, eyes, and neck. Several efficient ergonomic intervention ideas were explored to lessen the detrimental effects of WMSDs and preclude the development of WMSDs amongst the control centre operators.

A Logistic Regression Model for Biomechanical Risk Classification in Lifting Tasks.

Lifting is one of the most potentially harmful activities for work-related musculoskeletal disorders (WMSDs), due to exposure to biomechanical risk. Risk assessment for work activities that involve lifting loads can be performed through the NIOSH (National Institute of Occupational Safety and Health) method, and specifically the Revised NIOSH Lifting Equation (RNLE). Aim of this work is to explore the feasibility of a logistic regression model fed with time and frequency domains features extracted from signals acquired through one inertial measurement unit (IMU) to classify risk classes associated with lifting activities according to the RNLE. Furthermore, an attempt was made to evaluate which are the most discriminating features relating to the risk classes, and to understand which inertial signals and which axis were the most representative. In a simplified scenario, where only two RNLE variables were altered during lifting tasks performed by 14 healthy adults, inertial signals (linear acceleration and angular velocity) acquired using one IMU placed on the subject's sternum during repeated rhythmic lifting tasks were automatically segmented to extract several features in the time and frequency domains. The logistic regression model fed with significant features showed good results to discriminate "risk" and "no risk" NIOSH classes with an accuracy, sensitivity and specificity equal to 82.8%, 84.8% and 80.9%, respectively. This preliminary work indicated that a logistic regression model-fed with specific inertial features extracted by signals acquired using a single IMU sensor placed on the sternum-is able to discriminate risk classes according to the RNLE in a simplified context, and therefore could be a valid tool to assess the biomechanical risk in an automatic way also in more complex conditions (e.g., real working scenarios).

The use of electromyography and kinematic measurements of the lumbar spine during ergonomic intervention among workers of the production line of a foundry.

Purpose: Workers who perform repetitive movements are exposed to many risk factors leading to the occurrence of lumbar back pain. The aim of the research was to answer the question whether the ergonomic instruction conducted by a physiotherapist would change the tested range of motion of the segments of lumbar spine and the symmetry of the work of the torso and upper limbs muscles during work performed by foundry employees. Methods: The study included 12 foundry production line workers with musculoskeletal pain. The workstation was built in the laboratory that perfectly simulates work on the production line. The workers performed two activities from their daily work, i.e. transferring and moving a casting. They were then given ergonomic instruction by a physiotherapist and performed the assigned tasks again. During the activities, the electromyographic signal from five muscles was recorded in terms of symmetry of their work. The maximum angular ranges of the motor segments of the lumbar spine were measured using gyroscopes. Results: After the ergonomic instruction, the contralateral imbalance of muscle activity decreased statistically significantly during the first phase (p = 0.0004), second phase (p = 0.0002) and the third phase (p = 0.0069) of transferring the casting. While moving the casting , only erector spinae showed statistically significantly (p = 0.0131) more symmetrical work after the ergonomic instruction. During the transfer of the casting, statistically significantly lower values of the ranges of motion between the segments were obtained after carrying out the ergonomic instruction for the left (p = 0.0231) and right (p = 0.0032) lateral flexion. The ranges of movement between the segments differed statistically significantly for the flexion (p = 0.0117), extension (p = 0.0469) and left (p = 0.0031) and right lateral flexion movements (p = 0.0012). Conclusion: Conducting ergonomic instruction consisting in teaching the correct performance of a movement task reduced the contralateral imbalance of muscle activity and changes the ranges of movement of L1-S1 segments. The task of optimizing the load on the musculoskeletal system, including the lumbar spine, should be carried out by means of appropriate ergonomic instruction and multi-pronged measures, including analysis of the health of employees, their working environment and physical activity outside the workplace. Electromyography and measurements of the range of movement of the lumbar spine appear to be good tools for the evaluation of workplace ergonomics.

Quantifying high flexion postures in occupational childcare as they relate to the potential for increased risk of knee osteoarthritis.

High knee flexion postures, despite their association with increased incidences of osteoarthritis, are frequently adopted in occupational childcare. This study sought to define and quantify high flexion postures typically adopted in childcare to evaluate any increased likelihood of knee osteoarthritis development. Through video analysis of eighteen childcare workers caring for infant, toddler, and preschool-aged children, eight high knee flexion postures were identified and quantified by duration and frequency. An analysis of postural adoption by task was subsequently performed to determine which might pose the greatest risk for cumulative joint trauma. Childcare workers caring for children of all ages were found to adopt kneeling and seated postures for extended durations and at elevated frequencies, exceeding proposed thresholds for incidences of knee osteoarthritis development. Structured activities, playing, and feeding tasks demanded the greatest adoption of high flexion postures and should be evaluated to minimise the potential childcare-related risks of osteoarthritis. Practitioner summary: High knee flexion postures (kneeling, squatting, etc.) have been associated with increased incidences of knee injury yet are commonly adopted in childcare. Childcare workers' postures were examined through video analysis revealing that proposed adoption thresholds for knee health are commonly exceeded when caring for children of all ages. Abbreviations: OA: osteoarthritis; WSIB: workplace safety insurance board; CAD: Canadian Dollar; DK: dorsiflexed kneeling; PK: plantarflexed kneeling; SAK: single arm supported kneeling; DAK: double arm supported kneeling; FS: flatfoot squatting; HS: heels up squatting; FLRS: floor sitting; SS: side sitting or leaning; STLS: stool sitting; BR: bending and reaching.

Pay attention to the prevention and control of work-related musculoskeletal disorder / 环境与职业医学

The health impacts and economic burdens associated by work-related musculoskeletal disorders (WMSDs) have become an important issue in the field of occupational health. Compared with developed countries, we should more systematically carry out in-depth research and practice on occupational ergonomics, comprehensively understand ergonomic factors and their characteristics, and strengthen the intervention and health risk assessment of ergonomic risk factors in key workplaces based on specific production conditions of different industries, so as to prevent and control the occurrence and development of WMSDs. This article introduced the concept, signs, symptoms, risk factors, and currently identifiable site-specific WMSDs. This column presented new research progress from the aspects of ergonomic load assessment methods, the prevalence and related risk factors of WMSDs in different trades, and ergonomic intervention of WMSDs, aiming to provide reference and basis for future research.

Cognitive Ergonomics of Assembly Work from a Job Demands-Resources Perspective: Three Qualitative Case Studies.

In manufacturing companies, cognitive processing is required from assembly workers to perform correct and timely assembly of complex products, often with varied specifications and high quality demands. This paper explores assembly operators' perceptions of cognitive/mental workload to provide a holistic understanding of the work conditions that affect cognitive demands and performance. While the physical loading aspects of assembly work are well known, most empirical literature dealing with cognitive/mental loading in manufacturing tends to examine a few particular aspects, rather than address the issue with a holistic system view. This semi-structured interview study, involving 50 industrial assembly operators from three Swedish companies, explores how assemblers perceive that their cognitive performance and well-being is influenced by a wide variety of factors within the context of mechanical product assembly. The interview transcripts were analysed using a priori coding, followed by bottom-up Thematic Analysis. The results indicate that a variety of systemic effects on assemblers' cognitive performance can be classified as job demands or resources. Quite often, the absence of a resource mirrors a related demand, and "good assembly conditions", as described by the interviewees, often re-frame demands as desirable challenges that foster motivation and positive feelings towards the work. The identified demands and resources stem from task design, timing, physical loading, intrinsic and extrinsic motivators, social teamwork and the product's "interface" design. Despite organisational differences and conditions between the three companies that took part in the study, the results are largely consistent.

A possible revival of population-representing digital human manikins in static work situations - exemplified through an evaluation of a prototype console for robotic surgery.

BACKGROUND: In the 90s, digital human manikins (DHMs) were introduced in planning of workstations, by static or semi-static simulations. Modern DHMs can simulate dynamic work and offer a rapid way for a virtual pre-production ergonomic evaluation. Work-related musculoskeletal disorders may affect surgical performance and patient safety. A prototype of an open console, which is contrary to the conventional closed consoles and may be seen as a representative for a new generation, has been designed to reduce workload for robotic surgery surgeons. OBJECTIVE: The aim of this project was to test a new DHM tool with improved usability to evaluate the ergonomics of a console of a robotic surgical system in a pre-production stage. METHODS: The DHM tool IMMA was used together with a 3D model of the prototype console. Twelve manikins who represented females and males from two national populations were introduced. Manikin-console distances, after console adjustments per manikin, were compared with a US checklist and Swedish standard for VDU work. RESULTS: The DHM tool was useful for this case, but the distances of the checklist and the standard were needed to be obtained "manually". The automatic functions of the DHM worked smoothly but were not optimized for VDU work. The prototype fulfilled most, but not all, of the ergonomic criteria of the checklist and the standard. CONCLUSIONS: There is room for improvements of the adjustable ranges of the console prototype. DHMs may facilitate rapid pre-production evaluation of workstations for static work; if ergonomic assessment models for VDU work are built-in, there may be a revival of DHMs in static work situations.

Classification of high knee flexion postures using EMG signals.

BACKGROUND: High knee flexion postures are often adopted in occupational settings and may lead to increased risk of knee osteoarthritis. Pattern recognition algorithms using wireless electromyographic (EMG) signals may be capable of detecting and quantifying occupational exposures throughout a working day. OBJECTIVE: To develop a k-Nearest Neighbor (kNN) algorithm for the classification of eight high knee flexion activities frequently observed in childcare. METHODS: EMG signals from eight lower limb muscles were recorded for 30 participants, signals were decomposed into time- and frequency-domain features, and used to develop a kNN classification algorithm. Features were reduced to a combination of ten time-domain features from 8 muscles using neighborhood component analysis, in order to most effectively identify the postures of interest. RESULTS: The final classifier was capable of accurately identifying 80.1%of high knee flexion postures based on novel data from participants included in the training dataset, yet only achieved 18.4%accuracy when predicting postures based on novel subject data. CONCLUSIONS: EMG based classification of high flexion postures may be possible within occupational settings when the model is first trained on sample data from a given individual. The developed algorithm may provide quantitative measures leading to a greater understanding of occupation specific postural requirements.

Bathing frail seniors at home: Home care providers' approaches.

BACKGROUND: Home care providers assisting with seniors' personal care often experience high rates of musculoskeletal disorders, particularly affecting the lower back. Assisting with bathing is consistently identified as one of their most physically demanding activities. OBJECTIVE: To identify and describe care providers' procedures for assisting a frail senior to bathe that are likely to contribute most to the development of back injuries. METHODS: Eight community-based personal support workers (home care aides) assisted a frail senior (actor) to bathe in a simulated home bathroom. Video recordings of the activity were coded according to providers' postures and to characterize techniques for providing care. RESULTS: Exposure to severe trunk flexion and high posture-induced back loads was greatest during transfers in and out of the bathtub. In particular, lifting the legs over the rim of the tub, assisting the client to shift across the bath transfer bench, and providing care to the legs and feet involved the care provider spending substantial time in highly flexed postures. No observed techniques for these activities showed substantially lower exposures. CONCLUSIONS: Further tools and/or techniques must be identified or developed to improve caregiver safety during these strenuous activities.

Decision support system for designing and assigning ergonomic workplaces to workers with disabilities.

Workers with disabilities are still lagging in employment rates compared to the healthy workforce. Those workers are also more sensitive for stress at work and possible injuries that are usually connected with non-adequate workplace design. Generally, absenteeism presents high costs for companies and costs can be even higher if injuries at work occur. Therefore, companies face the problem of identifying a suitable workplace for workers with disabilities and supplying the needed requirements. The purpose of our research was to develop a decision support system that would aid in the process of identifying and categorising disabilities of workers, and assigning the most suitable workplace with needed requirements in an integrated work environment to ensure high safety, productivity and satisfaction. The developed decision support system is also a step toward prevention of injuries at work. The usefulness of the system has been shown in a case study of a large-sized production company. Practitioner summary: The purpose of our research was to develop a decision support system that would aid companies to identify a suitable workplace for workers with disabilities with needed requirements in an integrated work environment to ensure high safety, productivity and satisfaction with lower costs. Abbreviations: OSHA: occupational safety and health act; UN Convention: The United Nations Convention; EU Directive 89/654/EEC: European Union directive concerning the minimum safety and health requirements for the workplace; ICF: The International Classification of Functioning, Disability and Health; ICD: The International Statistical Classification of Diseases and Related Health Problems; RULA: rapid upper limb assessment; OWAS: ovaco working analysing system.

Effect of a simulated tactical occupation task on physiological strain index, stress and inflammation.

Background. This study aimed to evaluate the physiological strain index (PSI) along with specific immune system markers in response to a simulated firefighting occupation workload. Methods. Ten healthy male adults completed a 6-min simulated fire stair climb (SFSC) at 60 steps/min. The protocol consisted of four conditions, some including wearing a 34.04-kg vest to simulate personal protective equipment (PPE) and/or inclusion of a color-word interference test (CWIT) as a distracting mechanism. The PSI was evaluated by continuously monitoring the heart rate and core temperature. Salivary cortisol (CORT) was measured at baseline, mid SFSC and post SFSC. C-reactive protein (CRP) was evaluated at baseline and 1 h post SFSC. Results. Repeated-measures analysis of variance showed a significantly different PSI across conditions (p = 0.001). A significantly elevated PSI was exhibited during all 6 min of SFSC for both PPE and PPE + CWIT conditions. Neither CORT (p = 0.116) nor CRP (p = 0.700) was significantly different across conditions or from baseline. Conclusion. These findings suggest that firefighters are potentially at a substantial degree of physiological stress from exercise and the weight of gear alone. Further work should be conducted to further evaluate the usefulness of the PSI as a means to monitor firefighters during fire suppression.

Influence of handle shape and size to reduce the hand-arm vibration discomfort.

BACKGROUND: Non-automated tool handles transmit a large magnitude of vibration to operators' hands, causing discomfort and pain. Therefore, the need for a better handle design is a matter of prime concern to overcome musculoskeletal disorders such as hand-arm vibration syndrome. OBJECTIVE: This study aimed to examine the influence of handle shapes in reducing the transmission of hand-arm vibration. METHODS: Seven different handles were designed and fabricated using 3D printing technology at the SSN College of Engineering, with consideration for the anatomical shape of the hand. The frequency-weighted Root Mean Square (RMS) values of the vibration levels transmitted were recorded at the wrist of twelve subjects, unaffected by musculoskeletal disorders. Subjective ratings of vibration and comfort perception were measured using the Borg Scale of Perceived Exertion. RESULTS: The total vibration value (ahv) of each of the six novel prototype handles (B-G) was compared to that of the reference handle denoted handle-A. The vibration reductions for handles B to G respectively were 0.542 m/s2 (14.59%), 0.481 m/s2 (12.95%), 0.351 m/s2 (9.45%), 0.270 m/s2 (7.27%), 0.407 m/s2 (10.96%) and 0.192 m/s2 (5.17%). CONCLUSIONS: A significant level of vibration reduction was achieved by the prototype handles. Qualitative feedback from the study subjects suggests that they were not aware of the levels of vibration being transmitted to the hand with each handle.

Analysis of Required Investigations of Work-Related Musculoskeletal Disorders in Spain.

Musculoskeletal disorders (MSD) are the most common source of occupational health problems in Western countries. In Spain, musculoskeletal disorders (MSDs) can be reported either as accidents or occupational diseases. When reported as an occupational disease, a full diagnosis is performed, as the compensation system needs the approval of the social security authority and a mandatory investigation has to be performed. Although many methods are available for investigating the causes of occupational accidents, occupational diseases have not been analysed with the same depth, and there is a lack of investigation methods. This paper aims to analyse the role of 43 occupational investigations of causes of musculoskeletal diseases in the prevention cycle. This study is based on the occupational investigations performed by workplaces' occupational health and safety specialists when musculoskeletal diseases are reported. The analysis of the data involves descriptive statistics and the Φ coefficient. Based on administrative data, 68 workplaces employing 15,260 workers were surveyed and 41 workplaces with 13,201 workers submitted valid questionnaires to be analysed. The most frequent cause of reported musculoskeletal disease, in terms of primary risk, is repetitive movement. The only proposed measure with a significant association to the exposure by repetitive movements is job rotation (alternating workers between tasks within a job or between activities as a means to vary different levels of exposure). The investigation of occupational diseases has been useful in most of the cases for proposing preventive measures. Most of the workplaces surveyed have performed investigations and adopted preventive measures, but the managers of some workplaces were not aware of any disease notification regarding their workers when surveyed. More research is needed to provide tools for this important task.

Visualizing stressful aspects of repetitive motion tasks and opportunities for ergonomic improvements using computer vision.

Patterns of physical stress exposure are often difficult to measure, and the metrics of variation and techniques for identifying them is underdeveloped in the practice of occupational ergonomics. Computer vision has previously been used for evaluating repetitive motion tasks for hand activity level (HAL) utilizing conventional 2D videos. The approach was made practical by relaxing the need for high precision, and by adopting a semi-automatic approach for measuring spatiotemporal characteristics of the repetitive task. In this paper, a new method for visualizing task factors, using this computer vision approach, is demonstrated. After videos are made, the analyst selects a region of interest on the hand to track and the hand location and its associated kinematics are measured for every frame. The visualization method spatially deconstructs and displays the frequency, speed and duty cycle components of tasks that are part of the threshold limit value for hand activity for the purpose of identifying patterns of exposure associated with the specific job factors, as well as for suggesting task improvements. The localized variables are plotted as a heat map superimposed over the video, and displayed in the context of the task being performed. Based on the intensity of the specific variables used to calculate HAL, we can determine which task factors most contribute to HAL, and readily identify those work elements in the task that contribute more to increased risk for an injury. Work simulations and actual industrial examples are described. This method should help practitioners more readily measure and interpret temporal exposure patterns and identify potential task improvements.

Occupational musculoskeletal disorders management using Fuzzy TOPSIS Assessment of Repetitive Tasks (ART).

BACKGROUND: In order to evaluate occupational disorders and ergonomic problems in a workplace, Multiple Criteria Decision Making (MCDM) problem solving methods such as Fuzzy Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) can be utilized. OBJECTIVE: In this paper, Musculoskeletal Disorder (MSD) risk factors were evaluated in a manufacturing company in Iran by a method called Assessment of Repetitive Tasks (ART) of the upper limbs integrated with Fuzzy TOPSIS in order to prioritize the corrective actions. METHODS: This study was done with a descriptive-analytical approach. The company under study had 240 employees who were working in seven different shops. Out of all tasks, 13 tasks were included in the study. Required information was gathered by a demographic questionnaire and ART method. Also, Fuzzy TOPSIS was utilized for the prioritization of the company shops based on the ergonomic control needs. RESULTS: Data analysis from ART indicated that 74.6% of the reviewed tasks were high risk. Based on the F- TOPSIS-ART results, Production shop prioritized as the highest need for MSD control. CONCLUSIONS: Because there is time and financial resources limit in ergonomic control activities, a fuzzy prioritization approach such as Fuzzy TOPSIS ART can be used to take advantage of the available resources and control risks to as low as reasonably practicable (ALARP) level.

Integrating the Ergonomics Techniques with Multi Criteria Decision Making as a New Approach for Risk Management: An Assessment of Repetitive Tasks -Entropy Case Study.

BACKGROUND: Nowadays, the health work decision makers need to analyze a huge amount of data and consider many conflicting evaluation criteria and sub-criteria. Therefore, an ergonomic evaluation in the work environment in order to the control occupational disorders is considered as the Multi Criteria Decision Making (MCDM) problem. In this study, the ergonomic risks factors, which may influence health, were evaluated in a manufacturing company in 2014. Then entropy method was applied to prioritize the different risk factors. METHODS: This study was done with a descriptive-analytical approach and 13 tasks were included from total number of employees who were working in the seven halls of an ark opal manufacturing (240). Required information was gathered by the demographic questionnaire and Assessment of Repetitive Tasks (ART) method for repetitive task assessment. In addition, entropy was used to prioritize the risk factors based on the ergonomic control needs. RESULTS: The total exposure score based on the ART method calculated was equal to 30.07 ±12.43. Data analysis illustrated that 179 cases (74.6% of tasks) were in the high level of risk area and 13.8% were in the medium level of risk. ART- entropy results revealed that based on the weighted factors, higher value belongs to grip factor and the lowest value was related to neck and hand posture and duration. CONCLUSIONS: Based on the limited financial resources, it seems that MCDM in many challenging situations such as control procedures and priority approaches could be used successfully. Other MCDM methods for evaluating and prioritizing the ergonomic problems are recommended.

Peak activation of lower limb musculature during high flexion kneeling and transitional movements.

Few studies have measured lower limb muscle activation during high knee flexion or investigated the effects of occupational safety footwear. Therefore, our understanding of injury and disease mechanisms, such as knee osteoarthritis, is limited for these high-risk postures. Peak activation was assessed in eight bilateral lower limb muscles for twelve male participants, while shod or barefoot. Transitions between standing and kneeling had peak quadriceps and tibialis anterior (TA) activations above 50% MVC. Static kneeling and simulated tasks performed when kneeling had peak TA activity above 15% MVC but below 10% MVC for remaining muscles. In three cases, peak muscle activity was significantly higher (mean 8.9% MVC) when shod. However, net compressive knee joint forces may not be significantly increased when shod. EMG should be used as a modelling input when estimating joint contact forces for these postures, considering the activation levels in the hamstrings and quadriceps muscles during transitions. Practitioner Summary: Kneeling transitional movements are used in activities of daily living and work but are linked to increased knee osteoarthritis risk. We found peak EMG activity of some lower limb muscles to be over 70% MVC during transitions and minimal influence of wearing safety footwear.