Comparing the results of five lifting analysis tools

The objective of this study was to compare the results of the NIOSH, ACGIH TLV, Snook, 3DSSPP and WA L&I lifting assessment instruments when applied to a uniform task (lifting and lowering milk cases with capacities of 15 and 23l). To enable comparisons between the various lifting assessment instruments, the outputs of each method were converted to an exposure index similar to the NIOSH Lifting Index. All instruments showed higher exposures associated with lifting the 23l cases versus the 15l cases. The NIOSH, ACGIH TLV and Snook methods were similar in their results with respect to the pattern of exposure over various height levels and the differences in exposures associated with lifting 15 and 23l cases. However, the WA L&I and 3DSSPP predicted substantially lower exposures. The reasons for instrument differences are presented so that practitioners can better select the methods they need and interpret the results appropriately.     

OCRA: a concise index for the assessment of exposure to repetitive movements of the upper limbs

In the light of data and speculation contained in the literature, and based on procedures illustrated in a previous research project in which the author described and evaluated occupational risk factors associated with work-related musculoskeletal disorders of the upper limbs (WMSDs), this paper proposes a method for calculating a concise index of exposure to repetitive movements of the upper limbs. The proposal, which still has to be substantiated and validated by further studies and applications, is conceptually based on the procedure recommended by the NIOSH for calculating the Lifting Index in manual load handling activities. The concise exposure index (OCRA index) in this case is based on the relationship between the daily number of actions actually performed by the upper limbs in repetitive tasks, and the corresponding number of recommended actions. The latter are calculated on the basis of a constant (30 actions per minute), which represents the action frequency factor; it is valid—hypothetically—under socalled optimal conditions; the constant is diminished case by case (using appropriate factors) as a function of the presence and characteristics of the other risk factors (force, posture, additional elements, recovery periods). Although still experimental, the exposure index can be used to obtain an integrated and concise assessment of the various risk factors analysed and to classify occupational scenarios featuring significant and diversified exposure to such risk factors.     

Quantifying repetitive hand activity for epidemiological research on musculoskeletal disorders--part II: comparison of different methods of measuring force level and repetitiveness

This paper focuses on comparisons between the different methods of assessing repetitive hand activities. Various methods were used to measure hand force and repetitiveness of hand activities on 733 subjects in the study described by Bao et al. (2006). Two definitions of repetitiveness were used in analysis of detailed time studies of repetitive hand activities and four parameters of the American Conference of Governmental Industrial Hygienists (ACGIH) hand activity level (HAL) and the Strain Index methods were estimated by ergonomists and used to quantify repetitiveness. Hand forces were measured or estimated using three different methods: 1) measured with a force gauge or mimicked on a force gauge (force matching); 2) estimated by ergonomists using rating scales; 3) self-reports by subjects. The jobs were also evaluated using the ACGIH HAL and Strain Index methods when different repetitiveness quantification methods were used. Results showed that different definitions of repetitive exertion might lead to measuring different physical exposure phenomena and produce very different results. There were poor correlations between the measures of repetitiveness estimated by the different methods. Correlations between force quantifications using different methods were also poor. This suggests that parameters measured by different methods might not be interchangeable. Both the ACGIH HAL and Strain Index methods identified more 'hazardous' jobs when repetitiveness was estimated by ergonomists than when it was calculated by detailed time studies of forceful hand exertions. The Strain Index method identified more 'hazardous' jobs than the ACGIH HAL method. Overall, the between-methods agreements were found to be moderate to substantial.     

Analysis of hand pressure in different crutch lengths and upper-limb movements during crutched walking

Hand pressure in crutch is important as it is directly related to the comfort of the patients using crutches. However, little research has been done on dynamical hand pressure during crutched walking. This study investigated hand pressures and joint movements in the upper limb with the different crutch lengths during crutched walking. Twelve healthy male adults participated in the study, and performed crutch-supported walking at bi-crutch and single-foot way. A specific mat of pressure sensors was designed to measure the hand pressure of the palm and fingers and a motion capture system used to capture the movements at the shoulder and elbow. It was found that when walking speeds were between 0.5 and 1.0 m/s, maximum pressure and force were approximately 120 kPa and 100 N respectively in the hand; the ranges of motion were from 28 to 60 deg at the shoulder and from 15 to 30 deg at the elbow. The results showed that the pressure-time integral and force-time integral in the hand are higher when using a traditional standard crutch length than using longer or shorter lengths. The visual analogue scores of conformable degree showed that the participants are favourite for a traditional standard crutch length. The pressure and kinematic data collected provide a set of database available for crutch manufacturer, glove designer and clinicians as reference when they need.Relevance to industryCrutched walking usually causes hand uncomfortable or injury. Our study provides the first experimental data of hand pressures and the joint movements in the upper limbs at different crutch lengths. These results are valuable for devising gloves for patients, thus improving the life quality of the patients using crutch.     

Occupational risk and prolonged standing work in apparel sales assistants

BackgroundThe prolonged standing posture during work affects the risk of developing musculoskeletal disorders of the lower limbs, especially in lack of alternative sitting. While different ergonomic tools are available to assess and manage the postural risk of the back and the upper limbs, there is a dearth of methods relative to the lower limbs.ObjectivesThe aim of this study is to assess the postural risk of sales assistants working in a prolonged standing posture, focusing on critical issues for the lower limbs.Methodsand criteria: 70 sales assistants employed among 9 apparel stores in northern Italy participated in the study. An observational approach was adopted, together with the application of standard ergonomic tools (Rula, Reba, Strain Index, Ocra) to assess the postural risk. Estimates of energy expenditure and movement's patterns were obtained through continuous monitoring with the Sense Wear Armband. Discomfort of the lower limbs was subjectively rated on the Borg's Cr-10 scale at the end of the work shift. The leg circumference was measured on each worker at intervals along the work shift.ResultsThe work of sales assistants in the apparel retail sector is characterized by the prolonged standing posture which accounts for more than 80% of the work shift duration; alternation with walking phases occurs according to assigned tasks and work organization.Activities of the upper limbs and occasional adopted awkward postures are observed, with the postural indexes varying between medium-high level of risk. The average distance walked during the work shift is 3,4 km. The musculoskeletal discomfort of the lower limbs reaches a medium-high intensity (CR 4–5) in 75% of the workers at the end of the work shift. Small but significant variations in the leg circumference were detected between beginning-end of the work shift (increase) and between beginning-end of the break interval (decrease).ConclusionOur data suggest that an indefinite level of risk of developing discomfort and musculoskeletal disorders of the lower limbs is real in sales assistants who work in a prolonged standing posture. The lack of specific assessment tool and of preventive measures could aggravate the exposure level.     

The Strain Index (SI) and Threshold Limit Value (TLV) for Hand Activity Level (HAL): risk of carpal tunnel syndrome (CTS) in a prospective cohort

A cohort of 536 workers was enrolled from 10 diverse manufacturing facilities and was followed monthly for six years. Job physical exposures were individually measured. Worker demographics, medical history, psychosocial factors, current musculoskeletal disorders (MSDs) and nerve conduction studies (NCS) were obtained. Point and lifetime prevalence of carpal tunnel syndrome (CTS) at baseline (symptoms + abnormal NCS) were 10.3% and 19.8%. During follow-up, there were 35 new CTS cases (left, right or both hands). Factors predicting development of CTS included: job physical exposure (American conference of governmental industrial hygienists Threshold Limit Value (ACGIH TLV) for Hand Activity Level (HAL) and the Strain Index (SI)), age, BMI, other MSDs, inflammatory arthritis, gardening outside of work and feelings of depression. In the adjusted models, the TLV for HAL and the SI were both significant per unit increase in exposure with hazard ratios (HR) increasing up to a maximum of 5.4 (p = 0.05) and 5.3 (p = 0.03), respectively; however, similar to other reports, both suggested lower risk at higher exposures. Data suggest that the TLV for HAL and the SI are useful metrics for estimating exposure to biomechanical stressors. PRACTITIONER SUMMARY: This study was conducted to determine how well the TLV for HAL and the SI predict risk of CTS using a prospective cohort design with survival analysis. Both the TLV for HAL and the SI were found to predict risk of CTS when adjusted for relevant covariates.     

Analysis of hand pressures related to wheelchair rim sizes and upper-limb movement

Hand pressure is important in wheelchair design as it is directly related to the comfort or injury of the patients/sportsmen using the wheelchair. However, little research has been done on hand pressure during wheelchair propelling. This study aimed to measure hand pressures and joint movements in the upper limb with the different size of wheelchair rims during manual propulsion. Nine healthy adult subjects participated in the study, and they were required to perform wheelchair propelling at their self-comfortable way. A specific mat of pressure sensors was used to measure the hand pressure of the palm and a motion capture system to capture the movements at the shoulder and elbow. The results showed that under the condition of the speeds between 0.7–1.7 m/s, the mean hand pressures were ranged between 180 and 200 kPa on the palm; the ranges of motion were from 30° to 70° at the shoulder and from 15° to 50° at the elbow. The pressure and kinematic data collected provide a set of database available for wheelchair manufacturer, glove designer, clinicians and sports exerciser as reference when they need.Relevance to industryPushing wheelchair usually causes hand uncomfortable or injury. Our study provides the first experimental data of hand pressures associated the joint movements in the upper limbs at different sizes of push-rims. These results are valuable for devising gloves for patients, thus improving the life quality of the patients using wheelchair.     

A Review.of: “Consumer Behaviour and the Behavioural Sciences”. By S. H. Britt. (John Wiley & Sons, 1966.) [Pp. xxxii+592.] 87s.

Abstract

Data on biomechanical overload of the upper limb in animal facility operators are currently scanty. We decided to study this risk in a university animal facility. Eleven different tasks performed by operators were identified. For each of them, the biomechanical overload of the upper limb was evaluated by applying 4 different methods frequently used, hypothesising a task duration of 4 and 8 h. Then two ‘typical’ real working days of the examined facility were reconstructed, and the risk for operators was calculated using the OCRA Index, Checklist and Mini-Checklist. Considering the specific tasks, the results show some difference among methods, but the overall results show an acceptable/slight risk of biomechanical overload of the upper limb in animal facility operators during typical working days.

Practitioner Summary: Upper limb biomechanical overload (UL-BO) is a neglected risk in animal facilities. In a university facility, 11 different tasks were identified, and 2 typical working days were analysed. Even if some task at increased risk may exist, during typical working days, the overall results show that the risk of UL-BO in operators can be considered usually acceptable or, at worst, slight.     

Aviation deicing workers,global risk assessment of musculoskeletal injuries

Deicing technicians working from open baskets are exposed to ergonomic risks and fatigue. This study aims to assess the global risk of musculoskeletal injuries (MSIs) for this type of activity. An ergonomic study was conducted with the workers of a Canadian airport deicing operator during the winter of 2016–2017. Video recordings made it possible to observe the activities during the most intensive work shifts, as well as characterise and quantify (frequency and duration) the movements/postures of twelve human subjects. The resulting risk assessment identified the body structures submitted to exertion, analysed the efforts involved and globally assessed the forces exerted on the spine and upper limbs. This global risk assessment leads to the conclusion that the risks to the upper limbs are preoccupying and must be examined further.     

Evaluation of ergonomic working conditions among standing sewing machine operators in Sri Lanka

BackgroundStanding Sewing Machine Operators (SSMOs) are engaged in highly repetitive operations, and work while standing during their entire working hours. This leads to discomforts and Musculoskeletal Disorders (MSDs). However, there is a dearth of research in SSMOs’ working conditions.Objective: Aim of the study is to evaluate the prevalence of MSDs and related ergonomic risk factors among SSMOs in the Sri Lankan textile industry.Methods: The sample included 552 female sewing machine operators. Data were collected through self-reported questionnaires which included demographic, job-related factors and Cornell Musculoskeletal Discomfort Questionnaire [CMDQ], along with the application of validated ergonomic tools (Rapid Entire Body Assessment [REBA] and Strain Index [SI]) to assess the ergonomic risks amongst them. The inter-rater reliability test ensured the reliability among observers. An individual regression model was developed for each body parts to assess the associated risk factors.Results: The highest occurrence of musculoskeletal symptoms were in knee, foot, thigh, lower leg and lower back of SSMOs. REBA grand score (4–11) indicated that workers’ postures were at medium, high and very high risk levels necessitating evaluation to change. Moreover, SI indicated medium and high risk of upper extremity disorders. Finally, regression models revealed associated risk factors with musculoskeletal symptoms among various body parts including age, Body Mass Index (BMI), marital status, SSMO experience, job satisfaction, job stress, daily walking distance to the boarding place/factory, interest in job rotation and satisfaction with the design of sewing machine.Conclusion: The findings highlighted that the prevalence of discomfort and MSDs in the lower limbs were higher than in the upper limbs among SSMOs. The findings revealed the working conditions of SSMO and emphasised the need for ergonomic interventions to minimise the MSDs among them.Relevance to industryThe findings highlighted ergonomic risks among SSMOs and associated risk factors which will help managers and researchers better understand the working conditions of SSMOs. The identified risk factors could be considered during the implementation of standing sewing operation layouts and during the selection and allocation of new employees.     

Decrease of force capabilities as an index of upper limb fatigue

The aim of the study was to assess upper limb fatigue on the basis of the force change index (FCI), which expresses changes in developed force, and to demonstrate that this index differentiates muscle fatigue of the upper limb depending on external load. The study was performed on ten young men in 12 conditions of external load. Ten conditions characterized repetitive work in a two-period cycle, in which both or one of the periods were loaded, and two conditions characterized continuous work with constant load. The participants tried to maintain hand-grip force at an imposed level during a determined time in the standard upper limb posture. Changes in values of recorded force exerted during successive cycles were approximated by a regression function. In most cases there was a strong correlation between the measurement data and the logarithmic regression curve. However, several cases of lower external load showed absence of such correlation. In 75% of the cases, there were statistically significant differences between the values of FCI calculated for individual conditions of external load. That means that FCI not only expresses muscle fatigue quantitatively but also points to the differences in upper limb fatigue resulting from differences in the external load. The study results have shown that the developed index (FCI) can be applied for fatigue assessment and discrimination with a more sophisticated model of a repetitive task than just a simple two-period work and rest model.     

Decrease of force capabilities as an index of upper limb fatigue

The aim of the study was to assess upper limb fatigue on the basis of the force change index (FCI), which expresses changes in developed force, and to demonstrate that this index differentiates muscle fatigue of the upper limb depending on external load. The study was performed on ten young men in 12 conditions of external load. Ten conditions characterized repetitive work in a two-period cycle, in which both or one of the periods were loaded, and two conditions characterized continuous work with constant load. The participants tried to maintain hand-grip force at an imposed level during a determined time in the standard upper limb posture. Changes in values of recorded force exerted during successive cycles were approximated by a regression function. In most cases there was a strong correlation between the measurement data and the logarithmic regression curve. However, several cases of lower external load showed absence of such correlation. In 75% of the cases, there were statistically significant differences between the values of FCI calculated for individual conditions of external load. That means that FCI not only expresses muscle fatigue quantitatively but also points to the differences in upper limb fatigue resulting from differences in the external load. The study results have shown that the developed index (FCI) can be applied for fatigue assessment and discrimination with a more sophisticated model of a repetitive task than just a simple two-period work and rest model.     

When is light work heavy? Components of the physical workload of sewing machine operators working at piecework rates

Epidemiologists have associated the job of sewing machine operators with a high incidence of musculoskeletal and other health problems, despite its classifications as light work according to energy expenditure criteria. An ergonomic analysis was undertaken in a trouser factory in order to describe components of the physical load of this work: force exerted, repetitions, time allocation and postures. Work activity of ten operators was observed and timed in situ, and forces were measured with a dynamometer. The time required to sew one seam is very short, 10-15 s per trouser leg. This short cycle is repeated more than 1500 times during the work day, involving quasi-continuous movements of the same parts of the body. The fact that movements are repeated so many times means that small details of the task assume a great importance. During the work day, a substantial force is exerted, only part of which can be measured with current technology. By these measurements, operators lift an average 406.1 kg of trousers per day and exert an average total force of 2858.4 kg with the upper limbs and 24 267.9 kg with the lower limbs. The work posture is static: seated with upper back curved and head bent over the sewing machine. Movements of the upper limbs involve abduction and adduction of the shoulders while exerting a force. For the same task, there is considerable variation in the dimensions of workstations. Interviews were conducted to determine the types of musculoskeletal complaints. The components of work activity could be treated to these complaints and to existing epidemiological data on musculoskeletal problems among sewing machine operators. This type of detailed examination can be applied by health and safety personnel to identify task components which could be changed to minimize the probability of musculoskeletal problems.     

姿态特征结合2维傅里叶变换的步态识别

目的 针对现有步态识别方法易受携带物品、衣服变化等影响的问题,提出了将无肩姿态能量图、步态参数等姿态特征与步态参数的2维傅里叶变换相结合的步态识别算法。方法 基于姿态关节点序列提出忽略肩膀宽度信息的无肩姿态能量图,用以减弱衣服变化的影响;由于下肢受衣物及背包影响较小,提取3个或3个以上的下肢关节点局部结构参数,即提取中臀点与左右膝关节点、中臀点与左右踝关节点构成的两个三角形面积以及所有下肢关节点构成的多边形面积作为步态参数,增强下肢参数在步态识别中的作用;人在行走时,单肢体的运动具有一定的周期性,且肢体之间运动具有一定的协调性,用步态参数的2维幅度谱来表示单肢体运动的周期性与肢体之间运动的协调性,以提高步态参数的可区别性;在现有典型步态特征的基础上,融合本文提出的无肩姿态能量图、步态参数及其2维傅里叶变换幅度谱,采用多特征表示步态的方法,充分利用各特征的优点,提出加权平均与最大池化相结合的两层分数融合策略进行步态识别,提高了步态识别算法在携带物品、衣服变化和跨视角等条件下的正确率。结果 实验结果表明,在中国科学院自动化研究所发布的步态数据集CASIA-B上,本文方法在相同视角条件下,正常状态、背包状态和穿大衣状态的平均识别率分别为99.56%、99.23%和94.25%;在跨视角条件下,正常状态、背包状态和穿大衣状态的平均识别率分别为91.32%、85.34%和69.51%。与典型算法相比,穿大衣状态的识别率有显著提升。结论 本文方法采用加权平均与最大池化相结合的两层分数融合策略,综合利用各特征的优点及其适用场景,有效提高了步态识别的准确率,特别是减弱了衣服厚度、样式等变化对步态识别的影响。     

Modeling and Verification of a Bimanual-Coordinated Training System

Recently, much attention has been paid to the development of robots that support bilateral arm training in various patterns. However, traditional bimanual rehabilitation robots usually realized different training modes with the robot providing a corresponding force for the impaired limb or else achieved an active-assisted mode with the healthy limb providing an assisted force for the impaired one. This paper proposes a robot to support bimanual-coordinated training. Different training modes are realized with one limb providing a corresponding force for the other limb. Two upper limbs accomplish symmetric movements in each training mode. Motion tracking training in active-resisted and active-assisted modes was performed on 11 healthy subjects. After bimanual-coordinated training, position tracking precision was significantly improved. The preliminarily results confirmed the feasibility of the system for supporting healthy subjects in performing bimanual-coordinated training tasks and demonstrated the effectiveness of the system in improving bimanual-coordinated performance of healthy subjects. Such a system could be potentially useful for patients who are in need of motor function rehabilitation after incidents such as stroke.     

Wrist postures in the general population of computer users during a computer task

Computer activities have commonly been linked to the development of musculoskeletal disorders (MSDs) in the upper limbs. However, to understand the effects computer use has on such disorders, it is necessary to identify and classify the movements involved in performing common computer tasks, one of these being typing. Motion analysis techniques were adopted to determine the movements involved during a typing task. This involved markers being placed on the knuckles, wrists and forearms of participants. This marker configuration allowed for the flexion, extension, radial deviation, ulnar deviation and a combination of these movements to be calculated. The results in one plane of motion show a mean extension|flexion and radial|ulnar deviation of 18.825°?±?10.013° and 5.228°?±?11.703° respectively. The most common position in two planes of motion was 20° extension with a simultaneous 20° ulnar deviation (10.72%). The results depict an alternative method of categorizing wrist positions in two planes during computer use. Coincident wrist postures should be addressed as opposed to motion in a single plane as these postures may result in different ergonomic risk factors developing.     

Effect of transported mass and constant force on times for ballistic and visually-controlled movements

Abstract

A series of experiments are reported in which the effects of transferred mass and resistive/assistive forces were investigated for both ballistic and visually-controlled movements. The first experiment involved the transfer of mass in the horizontal plane so that only inertia] forces were present. This was followed by experiments in which movements were made with a purely resistive or assistive force, without the presence of increased inertia. Finally the effects of transferring mass in the vertical direction were investigated, where resistive/assistive forces were present due to gravity, as well as increased inertia force due to the transferred mass. Both theoretical and empirical models are presented for each of these cases. It was found that, for both ballistic and visually-controlled movements, the data were well accounted for simply by a component of added time proportional to the transferred mass or the magnitude of the constant force. This result is in agreement with the procedure used in some predetermined motion time systems.     

Effects of handle orientation,gloves, handle friction and elbow posture on maximum horizontal pull and push forces

Biomechanical models were evaluated for effects of handle orientation, handle material, gloves and arm posture on maximal pull/push force. Eight healthy subjects performed maximum pull/push exertions on handles with two different orientations and two different surface materials, using bare hand and two types of glove as well as two arm postures. The empirical data supported the proposed biomechanical models: Pull/push forces for the bare hand on a rubber handle decreased 10% when the handle was parallel to the pull/push direction, compared with when perpendicular to it. For parallel handles, pull/push forces further decreased with decreasing hand–handle friction coefficient (simulated by different handle materials and gloves). Pull force exerted by the bare hand was 29% greater when the elbow was extended than when flexed. Pull force was greater than push force (with bare hand and flexed elbow). The biomechanical models suggest that friction between the hand and handle limits pull/push forces for parallel handles. Elbow strength may be responsible for decreased pull force for the flexed elbow posture and decreased force for pull compared with push in the postures examined.

Statement of Relevance: Biomechanical models presented in this paper provide insights for causes of upper extremity strength limitations during pull/push tasks. Findings in this paper can be used directly in the design of workstation and objects to reduce fatigue and risk of musculoskeletal disorders.     

The Multitask General Exposure Index (MultiGEI): An original model for analysing biomechanical risk factors in multitask jobs featuring weekly,monthly and annual macro-cycles

The assessment of exposure to biomechanical risk factors requires multiple different working risk factors to be considered and integrated in some way to determine overall exposure levels and risk. A particular challenge is posed when workers rotate between different tasks not only on a daily basis but over longer macro-cycles (which may be weekly, monthly, or even annual). There may be large numbers of rotated manual tasks, each with a different level of exposure and distribution pattern. This makes the multitask analysis more complex insofar as it must factor in multiple work activities over extended periods of time. This article presents a new general model specifically adapted to evaluating multiple tasks rotating over longer macro-cycles: the MultiGEI (Multitask General Exposure Index). The MultiGEI model uses similar criteria to current models to study daily rotations in tasks involving repetitive movements and exertions of the upper limbs (OCRA method) and manual lifting (the Revised NIOSH Lifting Equation or RNLE and Sequential Lifting Index). It can be applied to a variety of production and service sectors (agriculture, building construction, cleaning, retail, packaging, canteens, healthcare, etc.). It can also be applied to data obtained by other methods (other than OCRA and RNLE, here not presented) that specifically consider the relevant aspects of which tasks, their duration and their intrinsic risk score. The proposed approach is presented along with examples of applications, and advantages and limitations are discussed. A video showing examples of calculations carried out using free software, is also available.     

A model for musculoskeletal disorder-related fatigue in upper limb manipulation during industrial vegetables sorting

In the agro-industrial sector there are many activities whose urgent rhythms can cause a considerable exposure to bio-mechanical risk factors. In the vegetable sorting sector the workers are subject to a several biomechanical risks, with due to repetitive movements of upper limbs, and operations that require a remarkable degree of strength.