A portable ergonomic observation method (PEO) for computerized on-line recording of postures and manual handling

Agreement between an expert-rated mini job exposure matrix of occupational biomechanical exposures to the lower body and technical measurements or observation: a method comparison study

OBJECTIVES

Investigating the agreement between an expert-rated mini job exposure matrix (JEM) of lower body exposures and technical measurements of worktime spent standing/walking and observation-based estimates of time spent kneeling/squatting and total load lifted per workday.

METHODS

We chose 16 job titles from the 121 job groups in the lower body JEM and included them in the mini JEM. New expert ratings for the mini JEM were performed by the same five occupational physicians who performed the ratings for the lower body JEM. For each job title and type of exposure, the exposure estimates were a mean of the five independent ratings. Technical measurements of standing/walking for all 16 job titles, and for 8 job titles workplace observations were performed of kneeling/squatting and total load lifted per workday. Data were collected from September to December 2015 and supplemented by data from the NOMAD and DPhacto studies collected between 2011 and 2013. All data were collected in Denmark. Agreement between expert-based and measured/observed lower body exposures by job titles was evaluated using Spearman's rank correlation, Bland-Altman plots evaluated systematic deviations and limits of agreement (LoA).

RESULTS

Standing/walking showed a rank correlation of 0.55, kneeling/squatting 0.83 and total load lifted per workday 0.71. The mini JEM estimates did not systematically deviate from the technical measurements/observations for time spent standing/walking (mean difference 0.20 hours/workday, LoA -1.63, 2.03 hours/workday) and kneeling/squatting (mean difference -0.35 hours/workday, LoA -1.21, 0.51 hours/workday). For total load lifted per workday, the mini JEM systematically overestimated the exposures compared with the observations (mean difference -909 kg/workday, LoA -3000, 1147 kg/workday).

CONCLUSIONS

There was moderate to very high agreement between an expert-rated mini JEM of standing/walking, kneeling/squatting, and lifting exposures and corresponding technical measurements/observations. This method comparison study supports the use of the expert-based lower body JEM in large-scale occupational epidemiological studies.

Measurements and observations of movements at work for warehouse forklift truck operators

Inclinometry and video analyses can provide objective measures of physical workloads. The study aim was to measure and observe arm, back and head postures and movements among forklift truck operators (FLTOs) during a working day, analyzing differences between types of forklift trucks and to assess reported workload and health. Twenty-five male FLTOs in a high-level warehouse were randomly included. The data collected comprised technical measurements, video analyses of postures and movements, and a questionnaire measuring health, pain and workload. On average, the FLTOs rotated their head more than 45°, in total, 232 times/h. Video analysis revealed that FLTOs periodically drive the forklift truck sideways with the head rotated in the direction of travel, and in periods look upwards, in which the head is highly rotated and extended. Inclinometry and observations during the working day has the potential to be a valuable part of risk assessment promoting occupational safety and health.

Bilén S. Wearable Inertial Measurement Unit Sensing System for Musculoskeletal Disorders Prevention in Construction

Construction workers executing manual-intensive tasks are susceptible to musculoskeletal disorders (MSDs) due to overexposure to awkward postures. Automated posture recognition and assessment based on wearable sensor output can help reduce MSDs risks through early risk-factor detection. However, extant studies mainly focus on optimizing recognition models. There is a lack of studies exploring the design of a wearable sensing system that assesses the MSDs risks based on detected postures and then provides feedback for injury prevention. This study aims at investigating the design of an effective wearable MSDs prevention system. This study first proposes the design of a wearable inertial measurement unit (IMU) sensing system, then develops the prototype for end-user evaluation. Construction workers and managers evaluated a proposed system by interacting with wearable sensors and user interfaces (UIs), followed by an evaluation survey. The results suggest that wearable sensing is a promising approach for collecting motion data with low discomfort; posture-based MSDs risk assessment has a high potential in improving workers’ safety awareness; and mobile- and cloud-based UIs can deliver the risk assessment information to end-users with ease. This research contributes to the design, development, and validation of wearable sensing-based injury prevention systems, which may be adapted to other labor-intensive occupations.

Physical Work Demands of Childcare Workers in Denmark: Device-Based Measurements and Workplace Observations Among 199 Childcare Workers from 16 Day Nurseries

Objectives

Childcare workers in Denmark have high prevalence of musculoskeletal pain (MSP) and sickness absence, but the existing knowledge of their physical work demands is limited, hampering preventive initiatives. This study aimed to assess the physical work demands with accelerometers and workplace observations of childcare workers handling children age 0–3.

Methods

Data collection consisted of an electronic survey, anthropometric measurements, accelerometer measurements providing information of physical activity types and postures with Acti4 software from five consecutive workdays, as well as 4-h visual workplace observation per childcare worker from 16 Danish nurseries.

Results

In total, 199 childcare workers were enrolled in the study. A total of 4181 working hours of accelerometer measurements and 722 h of workplace observations were carried out. Accelerometer measurements showed that they spent about half of the working day (44.8%) in sedentary postures, and the rest standing (22.8%), moving (13.0%), walking (14.6%), running (0.1%), and climbing stairs (0.7%), with 4.1% in knee straining postures (kneeling and squatting) and 4.3% forward trunk inclination >60°. Workplace observations showed that they carried children 1.8% of the working hours.

Conclusions

Physical work demands of Danish childcare workers are characterized by about half of the workday being sedentary, and the remaining of the workday being quite evenly distributed between standing and dynamic activities, with low exposures to carrying children. Their exposure to forward bending of the trunk and knee straining postures could impose a risk for MSP and sickness absence, and preventive initiatives should be considered.

Standardized photometric assessment method: A novel approach for the analysis of dental ergonomic posture

Background:

Identification and documentation of the proper and improper dental ergonomic postures have gained its importance in the recent years due to the increased prevalence of work-related musculoskeletal disorders (WMSDs) among dentists and dental students who do not practice proper ergonomic procedure.

Aim:

The aim of the present study is to analysis ergonomic posture among dental students while performing supragingival scaling (SGS) procedure, using the standardized photometric assessment method (SPAM).

Materials and Methods:

A total number of 90 students from the third year (III year) to final year (IV year) and internship (Intern) (30 each) were included in the study. All the 90 students were asked to perform SGS procedure and were photographed and analyzed using the current technique. Eight dental ergonomic postures were analyzed in this study and grouped according to the classification system developed for scoring dental ergonomic postures by Garbin et al., in 2011. Analysis of variance test with Bonferroni correction was used to statistically analyze the collected data.

Results:

The mean index value for III year, IV year and Intern were 2.00, 2.03, and 2.13, respectively, which was not statistically significant (P = 0.709).

Conclusions:

Analysis of the dental students using the current method showed that most of them come under inadequate and regular category which puts them in a high risk for developing WMSDs. The SPAM to analyze the dental ergonomic posture was simple and effective and should be further explored in the future studies for its pros and cons.

Inter-Rater Reliability of Ergonomic Work Demands for Childcare Workers Using the Observation Instrument TRACK

The aim of this study is to evaluate the inter-rater reliability of a newly developed instrument-TRACK (observaTion woRk demAnds Childcare worK) for observations of ergonomic work demands in childcare work. Two trained raters conducted thirty hours of concurrent observation of fifteen childcare workers in three different day nurseries. Inter-rater reliability of ergonomic work demands was evaluated using Gwet's Agreement Coefficient (AC₁) and interpreted by the Landis and Koch benchmark scale. Twenty ergonomic work demand items were evaluated. Inter-rater reliability was 'almost perfect' for nine items (AC₁ 0.81-1.00), 'substantial' for four items (AC₁ 0.61-0.80), 'moderate' for four items (AC₁ 0.41-0.60), 'fair' for two items (AC₁ 0.21-0.40), and 'slight' (AC₁ 0.00-0.20) for one item. No items had 'poor' (AC₁ < 0.00) agreement. The instrument is reliable for assessing ergonomic work demands in childcare in real-life settings.

A structural framework for sustainable processes in ergonomics

Considering today's globalised world, new concepts that assist ergonomics are needed to provide human well-being. Accordingly, the sustainability concept is used in this study to satisfy the needs of stakeholders, put environmentally-friendly and cost-effective interventions into practice and provide ergonomically well-designed and easily managed processes that are more flexible, adaptable and human-sensitive. To achieve this, a practical and easily adaptable framework, which integrates ergonomics and sustainability by presenting the relations between fundamental elements of ergonomics and sustainability dimensions (SDs), is proposed. Within this base framework, ergonomic indicators (EIs) and sub-dimensions proposed for the classification of EIs are structured for ergonomics under a sustainability point-of-view. The sub-dimensions proposed in this study, which have direct or indirect relations to humans, are 'Loss', 'Investment', 'Conditions', 'Contribution', 'Self-Development', and 'Satisfaction'. This structural framework, which can be easily used by ergonomists or managers, ensures a good starting point for providing sustainable processes in ergonomics. Practitioner summary: This study proposes a structural framework to present the relations between ergonomics and sustainability. In the context of ergonomics, fundamental elements of ergonomics are chosen, while three dimensions of sustainability and proposed sub-dimensions are used in the context of sustainability. The adapted ergonomic indicators are also classified within these sub-dimensions.Abbreviations: SDs: sustainability dimensions; SIs: sustainability indicators; EIs: ergonomic indicators.

Bibliometric analysis of the body posture in relation to visual display terminals (VDTs)

BACKGROUND

In modern society, there is an increase both in the demand and the duration of computer work. Failure to correct body posture while using the computer has become a serious health hazard.

OBJECTIVE

To identify global trends in research related to body posture and visual display terminals (VDTs) using a bibliometric approach.

METHODS

In the search process, the keywords (posture *) AND (computer* OR "visual display terminal") were used in the study title section, in the Wos, Scopus and Medline databases.

RESULTS

149 references published between 1970 and 2016 were analyzed. The studied variables were the years of publication, authorship and collaboration index, publication type, titles of journals, most used languages, impact of the publications, as well as content of the articles.

CONCLUSIONS

In recent years, the studies on body posture in relation to VDT have been increased both in quantity and quality of publications. The analysis and/or design of the workplace, as well as the elements that make up the computer (keyboard and mouse) are the most researched topics in the area.

Improving work for the body - a participatory ergonomic intervention aiming at reducing physical exertion and musculoskeletal pain among childcare workers (the TOY-project): study protocol for a wait-list cluster-randomized controlled trial

Background

The prevalence of musculoskeletal pain (MSP) is persistently high throughout the world. Work-related factors such as high physical workload (lifting, bending and twisting of the back) are considered to be among the main causes of MSP. Work in childcare includes the need to lift, carry, and support children in a range of activities, requiring several demanding postures and movements, such as bending forward and twisting of the back and sitting on the floor. Participatory ergonomics may represent a solution for decreasing the physical workload to reduce MSP. We present the protocol of a study aiming to evaluate the effect and process of a participatory ergonomics intervention designed to reduce physical exertion during work and MSP (including MSP interfering with work) among childcare workers.

Methods/design

This study will use a two-arm cluster-randomized design employing a wait-list control, with childcare institutions forming the clusters. Three workshops will be conducted during the 4-month intervention period. Participants will identify risk factors for strenuous work and MSP, develop solutions for reducing the identified risk factors, and implement them in their team. An ergonomic consultant will guide the process. The data collection will consist of questionnaires and objective measures of heart rate and physical activity, observations of physical workload, and information on sickness absence based on company records. Primary outcomes are physical exertion during work and MSP (including pain-related work interference) measured at 4 months. Secondary outcomes measured at 4 months are sickness absence due to MSP; objectively measured occupational physical activity and heart rate; and self-reported self-efficacy, employee involvement, and need for recovery. Alongside the trial, a process evaluation and an economic evaluation will be conducted.

Discussion

The study will evaluate the effect and process of a participatory ergonomics intervention to reduce physical exertion at work and MSP among childcare workers. By performing a cluster-randomized controlled trial with an effect evaluation based on both objective and self-reported measures with the addition of a process evaluation and economic evaluation, this study will contribute to the evidence for prevention of MSP among a less studied occupational group. Results are expected in 2018–2019.

Trial registration

ISRCTN, ISRCTN10928313. Registered on 11 January 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2788-z) contains supplementary material, which is available to authorized users.

The Occurrence of Back Pain in School Children and Exposure to Risk Factors in Schools can they be Measured?

Back pain is a significant financial burden on industry and the economy, but more importantly it is the cause of suffering and disability to countless individuals. Therefore if the symptoms and risk factors of back pain could be identified at an early stage, the opportunities for remedial action would be improved. The study aims to identify the extent of back pain experienced by 11 to 14 year old school children, and establish the intensity, duration and frequency of exposure to mechanical risk factors present in schools. The following criteria were formulated to meet the study objectives, The method should record the intensity, duration, and frequency of the exposure, be continuous, unobtrusive, valid, reliable and feasible. None of the existing methods satisfied all the criteria, therefore new methods must be developed, or those methods which came closest to fulfilling the criteria, might be adapted to suit the participants and the research setting.

Ergonomic assessment for the task of repairing computers in a manufacturing company: A case study

BACKGROUND

Manufacturing industry workers who repair computers may be exposed to ergonomic risk factors.

OBJECTIVES

This project analyzes the tasks involved in the computer repair process to (1) find the risk level for musculoskeletal disorders (MSDs) and (2) propose ergonomic interventions to address any ergonomic issues.

METHODS

Work procedures and main body postures were video recorded and analyzed using task analysis, the Rapid Entire Body Assessment (REBA) postural method, and biomechanical analysis.

RESULTS

High risk for MSDs was found on every subtask using REBA. Although biomechanical analysis found an acceptable mass center displacement during tasks, a hazardous level of compression on the lower back during computer's transportation was detected.

CONCLUSIONS

This assessment found ergonomic risks mainly in the trunk, arm/forearm, and legs; the neck and hand/wrist were also compromised. Opportunities for ergonomic analyses and interventions in the design and execution of computer repair tasks are discussed.

Is what you see what you get? Standard inclinometry of set upper arm elevation angles

Previous research suggests inclinometers (INC) underestimate upper arm elevation. This study was designed to quantify possible bias in occupationally relevant postures, and test whether INC performance could be improved using calibration. Participants were meticulously positioned in set arm flexion and abduction angles between 0° and 150°. Different subject-specific and group-level regression models comprising linear and quadratic components describing the relationship between set and INC-registered elevation were developed using subsets of data, and validated using additional data. INC measured arm elevation showed a downward bias, particularly above 60°. INC data adjusted using the regression models were superior to unadjusted data; a subject-specific, two-point calibration based on measurements at 0° and 90° gave results closest to the 'true' set angles. Thus, inclinometer measured arm elevation data required calibration to arrive at 'true' elevation angles. Calibration to a common measurement scale should be considered when comparing arm elevation data collected using different methods.

Wearability assessment of a wearable system for Parkinson's disease remote monitoring based on a body area network of sensors

Wearable technologies for health monitoring have become a reality in the last few years. So far, most research studies have focused on assessments of the technical performance of these systems, as well as the validation of the clinical outcomes. Nevertheless, the success in the acceptance of these solutions depends not only on the technical and clinical effectiveness, but on the final user acceptance. In this work the compliance of a telehealth system for the remote monitoring of Parkinson's disease (PD) patients is presented with testing in 32 PD patients. This system, called PERFORM, is based on a Body Area Network (BAN) of sensors which has already been validated both from the technical and clinical point for view. Diverse methodologies (REBA, Borg and CRS scales in combination with a body map) are employed to study the comfort, biomechanical and physiological effects of the system. The test results allow us to conclude that the acceptance of this system is satisfactory with all the levels of effect on each component scoring in the lowest ranges. This study also provided useful insights and guidelines to lead to redesign of the system to improve patient compliance.

Statistical performance of observational work sampling for assessment of categorical exposure variables: a simulation approach illustrated using PATH data

Objectives:

Observational work sampling is often used in occupational studies to assess categorical biomechanical exposures and occurrence of specific work tasks. The statistical performance of data obtained by work sampling is, however, not well understood, impeding informed measurement strategy design. The purpose of this study was to develop a procedure for assessing the statistical properties of work sampling strategies evaluating categorical exposure variables and to illustrate the usefulness of this procedure to examine bias and precision of exposure estimates from samples of different sizes.

Methods:

From a parent data set of observations on 10 construction workers performing a single operation, the probabilities were determined for each worker of performing four component tasks and working in four mutually exclusive trunk posture categories (neutral, mild flexion, severe flexion, twisted). Using these probabilities, 5000 simulated data sets were created via probability-based resampling for each of six sampling strategies, ranging from 300 to 4500 observations. For each strategy, mean exposure and exposure variability metrics were calculated at both the operation level and task level and for each metric, bias and precision were assessed across the 5000 simulations.

Results:

Estimates of exposure variability were substantially more uncertain at all sample sizes than estimates of mean exposures and task proportions. Estimates at small sample sizes were also biased. With only 600 samples, proportions of the different tasks and of working with a neutral trunk posture (the most common) were within 10% of the true target value in at least 80% of all the simulated data sets; rarer exposures required at least 1500 samples. For most task-level mean exposure variables and for all operation-level and task-level estimates of exposure variability, performance was low, even with 4500 samples. In general, the precision of mean exposure estimates did not depend on the exposure variability between workers.

Conclusions:

The suggested probability-based simulation approach proved to be versatile and generally suitable for assessing bias and precision of data collection strategies using work sampling to estimate categorical data. The approach can be used in both real and hypothetical scenarios, in ergonomics, as well as in other areas of occupational epidemiology and intervention research. The reported statistical properties associated with sample size are likely widely relevant to studies using work sampling to assess categorical variables.

Cost-efficient measurement strategies for posture observations based on video recordings

Assessment of working postures by observation is a common practice in ergonomics. The present study investigated whether monetary resources invested in a video-based posture observation study should preferably be spent in collecting many video recordings of the work and have them observed once by one observer, or in having multiple observers rate postures repeatedly from fewer videos. The study addressed this question from a practitioner's perspective by focusing two plausible scenarios: documenting the mean exposure of one individual, and of a specific occupational group. Using a data set of observed working postures among hairdressers, empirical values of posture variability, observer variability, and costs for recording and observing one video were entered into equations expressing the total cost of data collection and the information (defined as 1/SD) provided by the resulting estimates of two variables: percentage time with the arm elevated <15° and >90°. Sixteen measurement strategies involving 1-4 observers repeating their posture ratings 1-4 times were examined for budgets up to €2000. For both posture variables and in both the individual and group scenario, the most cost-efficient strategy at any specific budget was to engage 3-4 observers and/or having observer(s) rate postures multiple times each. Between 17% and 34% less information was produced when using the commonly practiced approach of having one observer rate a number of video recordings one time each. We therefore recommend observational posture assessment to be based on video recordings of work, since this allows for multiple observations; and to allocate monetary resources to repeated observations rather than many video recordings.

The effect of camera location on observation-based posture estimation

This study used the observation-based method showing images on computer to evaluate angle estimation errors of 8 body segments in 3 motion planes at up to 28 segment angles and 5 camera locations with respect to goniometric measurements. Thirty observers participated in evaluating segment angles. Forearm (9.9°) and thigh (9.5°) had smaller errors than hand (14.0°) and foot had the smallest error (8.7°) due to its narrow range of motion (ROM). Errors were small with camera locations perpendicular to motions in the planes, such as 90° camera location for the flexion and extension of arm (6.3°), forearm (7.9°), thigh (6.5°), and leg (8.1°) in the sagittal plane. Segments had small errors of 3.1°, 4.6°, and 3.8° at segment angles of -90°, 0° and 90°, respectively. Care should be taken when estimating angles by the observation-based method for a specific segment motion and viewing direction is suggested to be perpendicular to the motion plane.

PRACTITIONER SUMMARY

Some companies may not allow many cameras or have obstacles for working posture evaluation in the workplace. These study results can be a guideline on proper selection of the number of cameras and their locations for a specific segment and its motion of interest to reduce visual segment angle estimation errors.

Bias and imprecision in posture percentile variables estimated from short exposure samples

Background

Upper arm postures are believed to be an important risk determinant for musculoskeletal disorder development in the neck and shoulders. The 10^th and 90^th percentiles of the angular elevation distribution have been reported in many studies as measures of neutral and extreme postural exposures, and variation has been quantified by the 10^th-90^th percentile range. Further, the 50^th percentile is commonly reported as a measure of "average" exposure. These four variables have been estimated using samples of observed or directly measured postures, typically using sampling durations between 5 and 120 min.

Methods

The present study examined the statistical properties of estimated full-shift values of the 10^th, 50^th and 90^th percentile and the 10^th-90^th percentile range of right upper arm elevation obtained from samples of seven different durations, ranging from 5 to 240 min. The sampling strategies were realized by simulation, using a parent data set of 73 full-shift, continuous inclinometer recordings among hairdressers. For each shift, sampling duration and exposure variable, the mean, standard deviation and sample dispersion limits (2.5% and 97.5%) of all possible sample estimates obtained at one minute intervals were calculated and compared to the true full-shift exposure value.

Results

Estimates of the 10^th percentile proved to be upward biased with limited sampling, and those of the 90^th percentile and the percentile range, downward biased. The 50^th percentile was also slightly upwards biased. For all variables, bias was more severe with shorter sampling durations, and it correlated significantly with the true full-shift value for the 10^th and 90^th percentiles and the percentile range. As expected, shorter samples led to decreased precision of the estimate; sample standard deviations correlated strongly with true full-shift exposure values.

Conclusions

The documented risk of pronounced bias and low precision of percentile estimates obtained from short posture samples presents a concern in ergonomics research and practice, and suggests that alternative, unbiased exposure variables should be considered if data collection resources are restricted.

Cost efficiency comparison of four video-based techniques for assessing upper arm postures

Many video-based techniques for assessing postures at work have been developed. Choosing the most appropriate technique should be based on an evaluation of different alternatives in terms of their ability to produce posture information at low input costs, i.e. their cost efficiency. This study compared four video-based techniques for assessing upper arm postures, using cost and error data from an investigation on hairdressers. Labour costs associated with the posture assessments from the video recordings were the dominant factor in the cost efficiency comparison. Thus, a work sampling technique associated with relatively large errors appeared, in general, to be the most cost-efficient because it was labour-saving. Measurement bias and other costs than labour cost for posture assessment influenced the ranking and economic evaluation of techniques, as did the applied measurement strategy, i.e. the numbers of video recordings and repeated assessments of them.

PRACTITIONER SUMMARY

The cost efficiency of four video-based techniques for assessing upper arm postures was compared. Work sampling techniques were in general more cost efficient than continuous observations since they were labour-saving. Whilst a labour cost dominated the comparison, 'hidden costs', bias and measurement strategy also influenced this dominance.

The influence of training on decision times and errors associated with classifying trunk postures using video-based posture assessment methods

The purpose of this study was to examine the influence of training on the decision times and errors associated with video-based trunk posture classifications. Altogether, 30 amateur and 30 knowledge-based participants completed a three-phase study (pre-training, training, post-training) that required them to classify static trunk postures in images on a computer screen into a posture category that represented the angle of the trunk depicted. Trunk postures were presented in both flexion/extension and lateral bend views and at several distances from the boundaries of the posture categories. Both decision time and errors decreased as distance from the boundaries increased. On average, amateur analysts experienced a larger decrease in decision time per posture classification than knowledge-based analysts (amateur: 0.79 s, knowledge-based: 0.60 s; p <0.05) suggesting that training can have beneficial effects on classification performance. The implications are that the analysis time associated with video-based posture assessment methods can be reduced with appropriate training, making this type of approach feasible for larger-scale field studies. Statement of Relevance:Understanding the role that training can play in reducing errors associated with the use of video-based posture assessment methods may result in more efficient use of these tools by ergonomic practitioners. Reducing decision time and misclassification errors will provide a more efficient, accurate and representative assessment of injury risk.

The ability of limited exposure sampling to detect effects of interventions that reduce the occurrence of pronounced trunk inclination

Ergonomics interventions often focus on reducing exposure in those parts of the job having the highest exposure levels, while leaving other parts unattended. A successful intervention will thus change the form of the job exposure distribution. This disqualifies standard methods for assessing the ability of various exposure measurement strategies to correctly detect an intervention's effect on the overall job exposure of an individual worker, in particular for the safety or ergonomics practitioner who with limited resources can only collect a few measurements. This study used a non-parametric simulation procedure to evaluate the relationship between the number of measurements collected during a self-paced manufacturing job undergoing ergonomics interventions of varying effectiveness, and the probability of correctly determining whether and to which extent the interventions reduced the overall occurrence of pronounced trunk inclination, defined as an inclination of at least 20 degrees . Sixteen video-recordings taken at random times on multiple days for each of three workers were used to estimate the time distribution of each worker's exposure to pronounced trunk inclination. Nine hypothetical ergonomics intervention scenarios were simulated, in which the occurrence of pronounced trunk inclination in the upper 1/8, 1/4, and 1/2 of the job exposure distribution was reduced by 10%, 30% and 50%. Ten exposure measurement strategies were explored, collecting from one to ten pre- and post-intervention exposure samples from an individual worker. For each worker, intervention scenario and sampling strategy, data were bootstrapped from the measured (pre-intervention) and simulated (post-intervention) exposure distributions to generate empirical distributions of the estimated intervention effect. Results showed that for the one to three intervention scenarios that had the greatest effect on the overall occurrence of trunk inclination in the job, one to four pre- and post-intervention measurements, depending on worker, were sufficient to reach an 80% probability of detecting that the intervention did, indeed, have an effect. However, even for the intervention scenario that had the greatest effect on job exposure, seven or more samples were needed for two of the three workers to obtain a probability larger than 50% of estimating the magnitude of the intervention effect to within +/-50% of its true size. For almost all interventions affecting 1/8 or 1/4 of the job, limited exposure sampling led to low probabilities of detecting any intervention effect, let alone its correct size.

Inter-rater reliability of PATH observations for assessment of ergonomic risk factors in hospital work

This study examined the inter-rater reliability of expert observations of ergonomic risk factors by four analysts. Ten jobs were observed at a hospital using a newly expanded version of the PATH method (Buchholz et al. 1996), to which selected upper extremity exposures had been added. Two of the four raters simultaneously observed each worker onsite for a total of 443 observation pairs containing 18 categorical exposure items each. For most exposure items, kappa coefficients were 0.4 or higher. For some items, agreement was higher both for the jobs with less rapid hand activity and for the analysts with a higher level of ergonomic job analysis experience. These upper extremity exposures could be characterised reliably with real-time observation, given adequate experience and training of the observers. The revised version of PATH is applicable to the analysis of jobs where upper extremity musculoskeletal strain is of concern.

Medical work Assessment in German hospitals: a Real-time Observation study (MAGRO) - the study protocol

BACKGROUND

The increasing economic pressure characterizes the current situation in health care and the need to justify medical decisions and organizational processes due to limited financial resources is omnipresent. Physicians tend to interpret this development as a decimation of their own medical influence. This becomes even more obvious after a change in hospital ownership i.e. from a public to a private profit oriented organization. In this case each work procedure is revised.To date, most research studies have focused mainly on differences between hospitals of different ownership regarding financial outcomes and quality of care, leaving important organizational issues unexplored. Little attention has been devoted to the effects of hospital ownership on physicians' working routines.The aim of this observational real time study is to deliver exact data about physicians' work at hospitals of different ownership.

METHODS

The consequences of different management types on the organizational structures of the physicians' work situation and on job satisfaction in the ward situation are monitored by objective real time studies and multi-level psycho diagnostic measurements.

DISCUSSION

This study is unique in its focus. To date no results have been found for computer-based real time studies on work activity in the clinical field in order to objectively evaluate a physician's work-related stress. After a complete documentation of the physicians' work processes the daily work flow can be estimated and systematically optimized. This can stimulate an overall improvement of health care services in Germany.

Interrater reliability of posture observations

OBJECTIVE

The aims of this research were (a) to study the interrater reliability of a posture observation method, (b) to test the impact of different posture categorization systems on interrater reliability, and (c) to provide guidelines for improving interrater reliability.

BACKGROUND

Estimation of posture through observation is challenging. Previous studies have shown varying degrees of validity and reliability, providing little information about conditions necessary to achieve acceptable reliability.

METHOD

Seven raters estimated posture angles from video recordings. Different measures of interrater reliability, including percentage agreement, precision, expression as interrater standard deviation, and intraclass correlation coefficients (ICC), were computed.

RESULTS

Some posture parameters, such as the upper arm flexion and extension, had ICCs > or = 0.50. Most posture parameters had a precision around the 10 degrees range. The predefined categorization and 300 posture categorization strategies showed substantially better agreement among the raters than did the 10 degrees strategy.

CONCLUSIONS

Different interrater reliability measures described different aspects of agreement for the posture observation tool. The level of agreement differed substantially between the agreement measures used. Observation of large body parts generally resulted in better reliability. Wider width angle intervals resulted in better percentage agreement compared with narrower intervals. For most postures, 30 degrees-angle intervals are appropriate. Training aimed at using a properly designed data entry system, and clear posture definitions with relevant examples, including definitions of the neutral positions of the various body parts, will help improve interrater reliability.

APPLICATION

The results provide ergonomics practitioners with information about the interrater reliability ofa postural observation method and guidelines for improving interrater reliability for video-recorded field data.

Relationships between observational estimates and physical measurements of upper limb activity

This study examined the internal validity of observational-based ergonomic job analysis methods for assessing upper limb force exertion and repetitive motion. Six manual tasks were performed by multiple 'workers' while direct measurements were made to quantify force exertion and kinematics of the upper limb. Observational-based analyses of force and upper limb motion/repetition were conducted by 29 professional ergonomists. These analysts overestimated the magnitude of individual force exertions - temporal aspects of force exertion (duty cycle) were estimated more accurately. Estimates of the relative severity of repetitive motions among the jobs were accurate. Absolute counts of repetitive motions were less accurate. Modest correlations (r(2) = 0.28 to r(2) = 0.50) were observed between ratings of hand activity level and measured joint velocities. Ergonomic job analyses relying on systematic observation should be applied and interpreted with consideration given to the capabilities and limitations of analysts in estimating the physical risk factors. These findings are relevant to a better understanding of the internal validity of ergonomic job analysis methods based on systematic observation.

Development and evaluation of an observational Back-Exposure Sampling Tool (Back-EST) for work-related back injury risk factors

We developed and evaluated an observational Back-Exposure Sampling Tool. A literature review suggested 53 exposure variables; these were reduced to 20 following field trials. Kappas for agreement beyond chance between six observers assessing exposures in 72 photos ranged from 0.21 to 1.0, with the highest values for posture type, trunk angle, manual materials handling, hands on item, and load weight. Intraclass correlations for agreement between pairs observing 17 workers once per minute for a full-shift were >0.74 for most postural, trunk angle, and manual materials handling variables. In validity testing, the proportions of shifts in flexion/extension and lateral bending observed for 169 full-shifts were compared to inclinometer measurements. Pearson correlations were 0.42 for 45-60 degrees flexion and 0.9 for >60 degrees flexion, but only 0.11-0.19 for lateral bending and trunk flexion less than 45 degrees . When lower flexion angles were collapsed to include trunk extension, correlations increased to >0.5.

Reliability of assessing upper limb postures among workers performing manufacturing tasks

The purpose of this study was to determine the inter- and intra-rater reliability of assessing upper limb postures of workers performing manufacturing tasks. Assessment of neck, shoulder, and wrist postures of 20 manufacturing employees was conducted by two raters observing digital video files using Multimedia Video Task Analysis (MVTA). Generalizability theory was used to estimate the inter- and intra-rater reliability. The results demonstrated good to excellent inter-rater reliability for neck and shoulder postures and fair to excellent inter-rater reliability for wrist postures. Intra-rater posture assessment demonstrated good to excellent reliability for both raters in all postures of the neck, shoulder, and wrist. This study demonstrated that posture assessment of manufacturing workers using MVTA is a reliable method.

Intervention practices in musculoskeletal disorder prevention: a critical literature review

Musculoskeletal disorders (MSDs) affect much of the workforce and remain a major form of occupational ill health. With a view to improving the efficacy of interventions, this review examined preventative actions relating to these disorders. A detailed analysis grid was used to classify the information contained in the 47 reviewed articles whose common aspect was to report actions carried out in the workplace that led to the implementation of changes to prevent MSDs. The analysis identified and characterized three major categories of intervention processes in MSD prevention: the complete type (n=17), the shortened type (n=16), and the turnkey type (n=14). These three groups of intervention processes were differentiated by their approaches and their contexts of application. The result was important differences in the changes implemented. Because of the variability in intervention processes and possible impacts on MSD prevention, a proposal to "delimit" these processes so as to improve their effectiveness is presented.

Classroom postures of 8-12 year old children

This study examined classroom postures of 8-12 year old school children in Flanders and related the outcomes to self-reported back or neck pain. Postural behaviours using the portable ergonomic observation (PEO) method and self-reported one-week back and neck pain were studied in 105 children from 41 different class groups. Pupils sat statically for 85% of the time, 28% of which the trunk was bent or flexed forward. For 9% of the time, children sat dynamically and for 36% they used a back rest. Children who spent more time sitting with a flexed trunk reported significantly more thoraco-lumbar pain compared to pain-free children and to children with cervical pain (p < 0.05). Children reporting pain stood for a longer period of time than pain-free children (p < 0.05). It is concluded that prolonged static kyphotic sitting without use of a backrest is common in elementary school children in Flanders.

The working postures among schoolchildren--a controlled intervention study on the effects of newly designed workstations

BACKGROUND

School workstations are often inappropriate in not offering an optimal sitting posture. The aim of this study was to investigate the effects of individually adjustable saddle-type chairs with wheels and desks with comfort curve and arm support on schoolchildren's working postures compared to conventional workstations.

METHODS

Ninety-seven participants aged 12-16 years were followed for 1 year, 47 at an intervention school and 50 at a control school. Anthropometrics and workstation dimensions were measured and working postures analyzed for a part of each group (n = 21, both groups) by means of video recording at baseline, before new workstations were introduced, and during follow-up.

RESULTS

There was a significant increase in upright back (p= .012) and neck (p= .019) postures in the intervention group compared to controls during follow-up. The saddle-type chairs allowed significantly greater trunk-thigh angles (p < .001) among participants than conventional chairs.

CONCLUSIONS

In schoolchildren, using individually adjustable saddle-type chairs and desks with comfort curve, a better match between workstations and anthropometric dimensions and improved working postures are obtained than using conventional workstations.

Validation of a self-administered questionnaire for assessing exposure to back pain mechanical risk factors

OBJECTIVE

To validate a self-administered questionnaire assessing exposure to mechanical risk factors, developed for a cohort study aiming at assessing the influence of physical and psycho-social factors on the incidence of low back pain (LBP).

METHODS

The study first involved a criterion validity test. A sample of the cohort workers (n=152) was observed at the workplace during four 30 min periods randomly distributed along the shift. At the end of the work shift, the questionnaire was filled in both by the worker and the observer. Agreements were tested between self-reports and observations, and between self-reports and observer opinion. Secondly, a comparison of exposure-effect relationships based on self-reports to those based on observations was carried out on the whole study cohort (n=716). Both sets of Relative Risks of being an incident case (LBP lasting at least 7 consecutive days in the follow-up year) were tested for heterogeneity.

RESULTS

Self-reports agreement levels were better with observer opinion than with observational data and were higher for answers at a dichotomous level. Vehicle driving, manual handling without estimation of weight and frequencies, or trunk bending without rotation showed a fair to good agreement with the external criteria. Limits in the validation procedure did not allow validating the sitting and standing durations. As regards the health outcome comparison, questionnaire and observations led to homogeneous Relative Risks for the variables tested.

CONCLUSIONS

Results show that self-reports provide a limited accuracy to assess actual frequencies and durations of work activities. Using a questionnaire, classifying the workers into exposure categories is rather relative, but questionnaire and observations seem similar in their relationships to outcome.

Trunk Flexion and Musculoskeletal Stress during Light Assembly Work

Mild trunk flexion held during working tasks throughout the day is considered a risk factor for low back pain. Exactly how the duration of these postures impacts the low back musculature during work tasks is not well understood. The objective of this study was to evaluate the effects of the temporal variation of mild trunk flexion and erect standing postures on low back discomfort and muscular fatigue, defined as a decrease in torso extension strength, during a realistic light assembly task. Study participants performed light assembly tasks for 20 minutes while in mild trunk flexion for periods of either 30 or 60 seconds, followed by recovery periods in which they stood erect, for periods of either 15, 30, 60, or 120 sec. Localized muscle discomfort, decreases in torso extension strength, and muscle activity of erector spinae were recorded. Duration of recovery period had a statistically significant effect on localized muscle discomfort of the lower back, upper back, and shoulders. Duration of trunk flexion and recovery time had an interactive effect on decreases in torso extension strength, for which strength decreased with decreasing recovery time and was more pronounced for trunk flexion periods of 60 sec rather than 30 sec. The mean RMS erector spinae muscle activity during mild trunk flexion was approximately 25% of the measured maximum voluntary RMS muscle activity across all conditions. The results suggest that it is the temporal pattern of muscular trunk flexion, and not the total time spent in trunk flexion, that affects localized discomfort and muscular fatigue of the low back.

Sitting habits in elementary schoolchildren: a traditional versus a "Moving school"

This study evaluated differences in sitting habits in the classroom between the project "Moving school" and a traditional school in 8-year-old children. Twenty-two children, since 1.5 years involved in the project were compared to 25 children in a traditional school. Making use of the Portable Ergonomic Observation (PEO) method, it was observed that children from a traditional school spend an average of 97% of the lesson time sitting statically, from which one-third with the trunk bend over 45 degrees. In the "Moving school" this posture was replaced by dynamic sitting (53%), standing (31%) and walking around (10%), while trunk flexion over 45 degrees was nearly not observed. Children from the "Moving school" also showed significantly less neck and trunk rotation. Additionally, accelerometric data showed significantly more physical activity in lessons of the "Moving school". Rates of self-reported back or neck pain did not differ significantly between both study groups. Results show that sitting habits are more favourable in a "Moving school". Further research is needed to study the impact of implementing "Moving school" concepts in traditional schools on sitting habits.

Classroom posture and self-reported back and neck pain in schoolchildren

The study reported here aims to identify the extent of back pain experienced by 11-14 year old schoolchildren, and establish the intensity, duration and frequency of exposure to physical risk factors present in schools. This paper considers the sitting postures of schoolchildren in the classroom. The sitting postures of 66 children were recorded in normal lessons using the Portable Ergonomic Observation Method (PEO). The study found significant associations between flexed postures and low back pain. Static postures and neck and upper back pain were also associated. This study has implications for schools, designers and people in the field of work related musculoskeletal disorders. Further research is required to examine the association between sitting posture and pain reported at different spinal locations.

Participatory Ergonomics Training in the Manufacturing Sector and Ergonomic Analysis Tools

This article discusses the importance of job analysis tools for training in the context of participatory ergonomic processes. It explains the major principles and challenges in the design of these tools for short-cycle repetitive tasks and for long-cycle varied tasks. The intervention framework is described and the proposed tools are presented and related to the literature. The participants’ difficulties with the tools developed in both contexts studied are summarized. The discussion suggests that these difficulties are partly related to the company context and raises questions about the data relevant for the evaluation of solutions in the case of non-repetitive tasks.

The use of the portable ergonomic observation method (PEO) to monitor the sitting posture of schoolchildren in the classroom

Contrary to common belief, back pain amongst young people is a frequent phenomenon. Epidemiological studies have found high prevalence rates of back pain amongst schoolchildren. The investigation reported here aims to validate children's self-reporting and the observation of sitting postures to establish the intensity, duration and frequency of exposure in the classroom. The sitting postures of 18 children were recorded using three methods, the portable ergonomic observation method (PEO), video analysis and self-report. The three methods were compared. PEO was significantly correlated with video analysis of the sitting postures after development of the method. Self-report was not significantly correlated with video analysis of the sitting postures. Therefore PEO was selected as the main observation tool in further analysis of children's sitting posture in schools in South-East England as part of a large research programme investigating back pain amongst schoolchildren.

Impact of observers' experience and training on reliability of observations for a manual handling task

Observation reliability (agreement percentage and kappa coefficients) for six experienced ergonomists and six untrained participants was computed. Participants were first tested after a training session and 1 week later after an additional practice session. Two formats were used: free practice and directed exercise. Reliability was tested for 17 variables and 20 sequences using photographic and video supports. The participants were asked to indicate whether they were confident about their answer, to rate this confidence on a scale of 1 to 10, and when the confidence rating was below 8, to provide a reason for this. Experience and additional practices had no clear impact on reliability, which was excellent overall. The main reason given was that the event to be observed took place at the borderline between two classes. The observers' rating on the scale appeared to be tied to the subsequent reliability computed. The use of a confidence scale appeared to be a useful tool for forecasting observation problems.

Assessment of work postures and movements using a video-based observation method and direct technical measurements

The aim was to study postures and movements during repetitive work using video-based observations and direct technical measurements (inclinometers and goniometers). A total of 21 healthy women from a poultry processing plant volunteered. Neck flexion > 20 degrees was registered during 92% of the recorded time with the observation method, while the corresponding value measured with the inclinometer was 65%. Different reference positions and different measured variables apparently contributed to the differences between the methods. Mean wrist position was measured to be 0 degrees in flexion-extension and 19 degrees in ulnar deviation. Differences between the methods in the registered hand positions were small. The number of repetitive movements/minute and mean power frequency (MPF) of the electrogoniometer data was significantly related, showing both variables to be relevant measures of repetitiveness. In conclusion, the observation method and the technical measurements supplemented each other well. A reduction in class categories was suggested for future observation methods.

Validity of fixed-interval observations for postural assessment in construction work

While observing six simulated construction tasks in the field, trained analysts recorded arm, trunk and leg postures categorically with two fixed-interval observational protocols. Observations were compared to measurements obtained with an electronic postural assessment system coupled with video analysis. The electronic postural assessment system consisted of electronic inclinometers to measure upper arm posture, knee flexion and trunk flexion, coveralls to house the inclinometer wiring, and an eletrogoniometric system to measure trunk lateral bending and twisting. Video analysis included frozen-frame analysis that corresponded to the moment of observation and simulated real-time analysis. Measurements were made on five male participants who each performed three tasks representative of construction laborers' work. Agreement among the observational and reference methods was generally high, although significant differences in measured frequency of exposure existed for knee flexion, trunk lateral bending and trunk twisting. The results suggest that, under appropriate conditions, discrete observations can be used to obtain reasonably accurate estimates of exposure frequency for broad categories of certain body postures.

Interobserver repeatability and validity of an observation method to assess physical loads imposed on the upper extremities

Interobserver repeatability and validity were assessed for a new semiquantitative, time-based observation method for the estimation of physical loads imposed on the upper extremities. Six risk factors of upper extremity disorders were included in the method: repetitive use of hand, use of hand force, pinch grip, non-neutral wrist posture, elevation of upper arm, local mechanical pressure. Two occupational health nurses were trained to use the method. They observed 127 work cycles at a food-processing plant and a paper mill. The method was validated against expert observations from the video, continuous recordings of myoelectric activity (EMG) of forearm muscles, and wrist posture measured with goniometers. Interobserver repeatability was good or moderate for repetitive use of hand, hand force, pinch grip (range kappa = 0.58-0.71 on the right; 0.60-0.61 on the left side). Interobserver repeatability was moderate or poor for non-neutral wrist posture, elevation of the upper arm and local mechanical pressure. Validity ranged from moderate to good for repetitive use of hand, use of hand force, pinch grip and non-neutral wrist posture when expert observation was used as reference standard. When observations were validated against force estimations (EMG) and wrist goniometer data, validity was poor. In the absence of generally accepted reference values, arbitrarily chosen limits were used for the proportional duration of some physical load factors. Studies should be carried out to assess the limits that best differentiate between safe and hazardous jobs.

Standing and very slow walking: foot pain-pressure threshold, subjective pain experience and work activity

Prolonged standing is described as uncomfortable by exposed workers, but the discomfort has not been linked to precise descriptions of workplace activity. We observed 10 sales and kitchen workers ("group 1") who worked standing. We compared the plantar pain-pressure threshold (PPT) of "group 1" (10 standing workers) to that of "group 2" (11 researchers who could choose their posture freely). Group 1 spent an average time of 62% standing still compared to 5% for group 2. Despite the fact that group 1 were primarily confined to defined areas and stood for 62% of the time, their mean time standing still was only 7 s. They walked 35% of the time, but 57% of walking sequences were only one or two steps. Group 1 PPT declined by 23% over the work day compared to 5% among group 2 (p < 0.05, ANOVA). Foot PPT is a promising quantitative indicator of effects of standing work.

Rapid entire body assessment (REBA)

This technical note details the preliminary stage in the development of a postural analysis tool, Rapid Entire Body Assessment (REBA). REBA has been developed to fill a perceived need for a practitioner's field tool, specifically designed to be sensitive to the type of unpredictable working postures found in health care and other service industries. A team of ergonomists, physiotherapists, occupational therapists and nurses collected and individually coded over 600 postural examples to produce a new tool incorporating dynamic and static postural loading factors, human-load interface (coupling), and a new concept of a gravity-assisted upper limb position. Initial reliability for inter-observer coding shows promise but further work is needed to establish the validity of the tool.

Current techniques for assessing physical exposure to work-related musculoskeletal risks, with emphasis on posture-based methods

Physical exposure to risks for potential work-related musculoskeletal injuries has been assessed using a variety of methods, including pen and paper based observation methods, videotaping and computer-aided analysis, direct or instrumental techniques, and various approaches to self-report assessment. These methods are critically reviewed in this paper. The applications of these techniques in ergonomic and epidemiologic studies are considered, and their advantages and shortcomings are highlighted. Finally, a strategy that considers both the ergonomics experts' view and the practitioners' needs for developing a practical exposure assessment tool is then discussed.

Validation of Portable Ergonomic Observation (PEO) method using optoelectronic and video recordings

The validity of the 'Portable Ergonomic Observation' method (PEO) was investigated against posture measurements based on continuous optoelectronic and video recordings made simultaneously with the observation. Work postures and actions during different frequently changing tasks were analyzed using both methods. In general, a high agreement between measured and observed data was achieved for the duration of clearly identifiable sustained postures and actions (such as repetitive movements of hands when typing), as well as for the frequency of clearly distinguishable actions (such as lifts). The agreement between observations and measurements was low for neck postures. In dynamic tasks the agreement was generally low. This was probably because of high levels of simultaneous information for the observer. No improvement in the agreement between measured and observed events could be achieved by leaving parts of the PEO categories unobserved at a time. Playback of video tapes to observe each category separately would increase the reliability of the observations but at the expense of increased time for the analysis.