This systematic review updates a previous systematic review on work-related physical and psychosocial risk factors for elbow disorders. Medline, Embase, Web of Science, Cochrane Central and PsycINFO were searched for studies on associations between work-related physical or psychosocial risk factors and the occurrence of elbow disorders. Two independent reviewers selected eligible studies and assessed risk of bias (RoB). Results of studies were synthesized narratively. We identified 17 new studies and lateral epicondylitis was the most studied disorder (13 studies). Five studies had a prospective cohort design, eight were cross-sectional and four were case-control. Only one study had no items rated as high RoB. Combined physical exposure indicators (e.g. physical exertion combined with elbow movement) were associated with the occurrence of lateral epicondylitis. No other consistent associations were observed for other physical and psychosocial exposures. These results prevent strong conclusions regarding associations between work-related exposures, and the occurrence of elbow disorders.

The aim of this study was to develop and evaluate calibration models to predict objectively measured time spent sitting, standing and walking during office work from self-reported time-use compositions using a compositional data analysis (CoDA) approach. Ninety-nine office workers (49 women) at the Swedish Transport Administration participated in an intervention study on relocation to activity-based offices. At baseline and at a 3-months follow-up, physical behaviours (sitting, standing and walking) at work were assessed for five days using a thigh-mounted accelerometer (Actigraph) and by self-report (IPAQ). The time-use composition of the three behaviours was expressed in terms of isometric log-ratios (ILR). Calibration models predicting accelerometry-based time-use from self-reported compositions were constructed using linear regression on baseline data, and then validated using follow-up data. The accelerometer data showed that, on average, workers spent 69.9% of their day sitting, 23.7% standing, and 6.4% walking. The corresponding percentages for self-reports were 71.7%, 21.6%, and 7.4%, respectively. Non-calibrated self-reports were biased: the RMS errors obtained from the ILRs expressing sitting, standing and walking were 0.73, 1.09 and 1.05, respectively. Calibration models reduced these errors by 45% (sitting), 56% (standing), and 76% (walking). Validation of the calibration models using follow-up data from the same workers showed calibration remained equally effective; RMS errors were reduced by 55% (sitting), 58% (standing), and 75% (walking). In conclusion, calibration models for compositional time-use data were effective in reducing bias in self-reported physical behaviours at work, and the models remained effective when used on new data from the same workers. Calibrated self-reports may represent a cost-effective method for obtaining physical behaviour data with a satisfying accuracy in large-scale cohort and intervention studies.

A study was conducted to investigate the influence of different approaches to arranging the pace and temporal organisation of repetitive assembly and disassembly tasks on both average performance and its variability and to compare assembly and disassembly times derived with psychophysical methods to a more traditional methods-time measurement (MTM) approach. The conditions studied were a traditional assembly line arrangement, where assemblies were started at a pace of 110 MTM (repeated on two occasions), a batch condition, where subjects were required to complete 36 assemblies within the total amount of time allowed at 110, MTM and a psychophysical condition, where subjects were allowed to choose their pace (repeated on two occasions). Overall, the results suggest that the mean time spent working in each cycle (the 'on-time') remained fairly constant across conditions, while the idle 'off-time' in between on-times was shorter and of less varied duration in the more autonomous batch and psychophysical conditions. During the second psychophysical (self-paced) condition, subjects completed a significantly higher number of assemblies than during the 110 MTM line condition. The higher pace was achieved through reduction in mean off-times and the potential implications for musculoskeletal risk are discussed. Statement of Relevance: Higher levels of autonomy over work pace, which intuitively would be beneficial from an ergonomics standpoint, actually led to subjects selecting to organise work such that off-times (idle times) were reduced. In contrast, active 'on' times were not affected much by autonomy. These results point to a reason that piecework would be associated with increased risk for musculoskeletal disorders.

This systematic review summarizes the evidence on associations between physical and psychosocial work-related exposures and the development of carpal tunnel syndrome (CTS). Relevant databases were searched up to January 2020 for cohort studies reporting associations between work-related physical or psychosocial risk factors and the incidence of CTS. Two independent reviewers selected eligible studies, extracted relevant data, and assessed risk of bias (RoB). We identified fourteen articles for inclusion which reported data from nine cohort studies. Eight reported associations between physical exposure and the incidence of CTS and five reported associations between psychosocial exposures and the incidence of CTS. Quality items were generally rated as unclear or low RoB. Work-related physical exposure factors including high levels of repetition, velocity, and a combination of multiple physical exposures were associated with an increased risk of developing CTS. No other consistent associations were observed for physical or psychosocial exposures at work and CTS incidence.

This study provides an overview on the relationships between exposure to work-related, hand-arm vibration and the occurrence of pre-defined disorders of the hands. We searched Medline, Embase, Web of Science, Cochrane Central, and PsycINFO for cross-sectional and longitudinal studies on the association between work-related vibration exposure and the occurrence of hand-arm vibration syndrome (including vibration-induced white finger), Dupuytren’s contracture, or hypothenar hammer syndrome. We used a 16-item checklist for assessing risk of bias. We present results narratively, and we conducted random effects meta-analyses if possible. We included 10 studies with more than 24,381 participants. Our results showed statistically significant associations between the exposure to hand-arm vibrations and the occurrence of the selected disorders, with pooled odds ratios ranging between 1.35 (95% CI: 1.28 to 2.80) and 3.43 (95% CI: 2.10 to 5.59). Considerable between-study hetereogeneity was observed. Our analyses show that exposure to vibrating tools at work is associated with an increased risk for the occurrence of selected disorders of the hands. Due to the majority of studies being cross-sectional, no firm conclusion is possible regarding causal relationships between vibration exposure and disorder occurrence. Future research should specifically address whether reducing the exposure to hand-held vibrating tools at work reduces the incidence of the disorders of the hands investigated in this systematic review.

We developed and evaluated calibration models predicting objectively measured sitting, standing and walking time from self-reported data using a compositional data analysis (CoDA) approach. A total of 98 office workers (48 women) at the Swedish Transport Administration participated. At baseline and three-months follow-up, time spent sitting, standing and walking at work was assessed for five working days using a thigh-worn accelerometer (Actigraph), as well as by self-report (IPAQ). Individual compositions of time spent in the three behaviors were expressed by isometric log-ratios (ILR). Calibration models predicting objectively measured ILRs from self-reported ILRs were constructed using baseline data, and then validated using follow-up data. Un-calibrated self-reports were inaccurate; root-mean-square (RMS) errors of ILRs for sitting, standing and walking were 1.21, 1.24 and 1.03, respectively. Calibration reduced these errors to 36% (sitting), 40% (standing), and 24% (walking) of those prior to calibration. Calibration models remained effective for follow-up data, reducing RMS errors to 33% (sitting), 51% (standing), and 31% (walking). Thus, compositional calibration models were effective in reducing errors in self-reported physical behaviors during office work. Calibration of self-reports may present a cost-e_ective method for obtaining physical behavior data with satisfying accuracy in large-scale cohort and intervention studies.

Background: Insufficient exposure assessment is a suggested contributing factor to the current lack of clearly characterised relationships between occupational biomechanical risk factors and musculoskeletal disorders. Minimal attention has been paid to the potential bias of measurement tools from expected true values (i.e. accuracy) or between measurement tools, and empirical data on the magnitudes of variance contributed by methodological factors for measurement tool precision are lacking.

Aim: The aim of this thesis was to quantify aspects of bias and precision in three commonly employed biomechanical risk factor assessment tools - inclinometry, observation, and electromyography (EMG) - and provide recommendations guiding their use. Methods: Upper arm elevation angles (UAEAs) were assessed using inclinometers (INC) and by computer-based posture-matching observation, and bias relative to true angles was calculated. Calibration models were developed for INC data, and their efficacy in correcting measurement bias was evaluated. The total variance of trapezius and erector spinae (ES) EMG recordings during cyclic occupational work was partitioned into biological and methodological sources, including the variance uniquely attributable to sub-maximal normalisation. Using algorithms to estimate the precision of a group mean, the efficacy of different trapezius EMG study designs was evaluated. Using precision criteria, the efficacy of different normalisation methods was assessed for ES EMG recordings.

Results and Discussion: Inclinometer measured UAEAs were biased from true angles, with increasing bias at higher angles. In contrast, computer based posture-matching observations were not biased from true angles. Calibration models proved effective at minimizing INC data bias. The dispersion of estimates between- and within- observers at any given set angle underlined the importance of repeated observations when estimating UAEAs. For EMG, a unique but relatively small component of the total variance was attributable to the methodological process of normalisation. Performing three repeats of the trapezius EMG normalisation task proved optimal at minimizing variance for one-day EMG studies, while two repeats sufficed for multi-day EMG studies. A prone normalisation task proved superior for maximizing normalised lumbar ES EMG precision.

Conclusion: Key aspects of measurement tool accuracy, bias between tools, and tool precision were quantified, and recommendations were made to guide future research study design.

Objective: To evaluate the efficacy of a nine-day accommodation protocol on reducing perceived discomfort while sitting on a stability ball (SB); trunk muscle activity levels and lumbar spinal postures were also considered.

Background: Previous studies have compared SB sitting to office chair sitting with few observed differences in muscle activity or posture; however, greater discomfort during SB sitting has been reported.  These findings may indicate an accommodation period is necessary to acclimate to SB sitting.

Methods: Six males and six females completed two separate, two-hour sitting sessions on an SB.  Half the participants completed a nine-day accommodation period between the visits while the other half did not use an SB during the time. On both occasions, self-reported perceived discomfort ratings were collected along with erector spinae and abdominal muscle activity and lumbar spinal postures.

Results: Discomfort ratings were reduced in female participants following the accommodation; no effects on muscle activation or lumbar spine postures were observed.

Conclusion: Accommodation training may reduce perceived low back discomfort in females. Trunk muscle activity and lumbar spine postures during seated office work on an SB did not differ between groups; however, greater sample power was required to conclusively address these variables.

Application: When deciding whether to use an SB in place of a standard office chair, this study indicates females electing to use an SB can decrease discomfort by following an accommodation protocol; no evidence was found to indicate SB chair use will improve trunk strength or posture, even following an accommodation period. 

Quantifying postures during work is a key aspect of understanding the physical loads experienced by the body at work. Two commonly used tools to assess posture are observation and inclinometry. Observation can be performed in many ways, from real-time observations made at the worksite assessing gross body postures, to estimates of individual joint angles made by observers assessing still images taken from video recorded at the work site. Inclinometry is a direct technical measurement tool which typically uses tri-axial accelerometers to determine angles of specific body segments with respect to the line of gravity. Regardless of which tool is used, it will introduce some variability between repeated measurements of a same posture – this is called method-logical variability. Over the past ten years we have worked extensively in our Cost-efficient measurement of physical exposures research program to quantify the magnitude of error resulting from different measurement strategies – both in terms of bias (that is, the difference between the truth and the measured values) and precision (that is, how different repeated estimates of a same posture are). Further, we have compared the monetary costs and relative performances (in terms of measurement quality) of different measurement strategies. From these studies we have developed a set of recommendations to guide effective posture assessment.

We assessed bias in both observation and inclinometry to determine how close posture estimates were to the true body segment angles. Under ideal observation conditions, observers were not biased in estimating upper arm elevation angles (1). Conversely, we found a systematic underestimation of upper arm elevation angles made using inclino-metry, particularly for angles at or above 60° (2). We developed a simple, on-body incli-nometry calibration procedure, and determined it was effective at reducing inclinometer bias (2).

We investigated how data sampling should be distributed within and across days, and how much data was required to obtain a specific level of precision. Regardless of the tool, we found that efficiency was improved by distributing shorter sampling periods using a fixed-interval strategy across an entire day or days rather than collecting one longer period (3,4). Precision of inclinometer data is high and thus a single measurement of an event is sufficient. In contrast, observation requires repeated estimates of an image, even under ideal conditions (1, 5). For observation of still images from videos, we determined that efficiency was improved by assessing images extracted at set intervals across the recorded data (i.e. a work sampling approach) rather than making estimates based on continuously viewed intervals of video data (5). Further, repeated observations by one or more observers of a smaller number of frames of data improved the precision of angle estimates compared with a single observer rating a larger number of frames (6). In the case that a worker is obstructed from the camera view, additional frame analysis may be required and the uncertainty of the angle estimate may increase (7).

We developed models to assess the net cost of each method, including equipment acquisition, data collection and data analysis. While the initial expense may seem higher for inclinometers, cost gains are made during collection and analysis stages compared to the work-intensive post-collection efforts required for observation. We found that inclinometry was more cost efficient than observation in certain settings (8), but that uncertainty exists even in cost assessment models and thus that cost-efficiency is situation-dependent (9).

There are strengths and weaknesses to both tools and one must evaluate the goals of each data collection and the relative merits of each tool when determining the appropriate assessment method. Observation may be preferable for studies seeking a general impression of a working day, identifying the tasks comprising a working day, assessing twisting during work, or assessing whether anatomical segments are loaded or supported during work. Inclinometers may be preferred for studies requiring full day or multi-day assessments, a high degree of accuracy and precision in angle estimates, information on segmental movement velocities, and/or studies where workers cannot be adequately filmed. Rapid advances in inclinometer technology and smart phone analogues will serve to further minimise set-up times and acquisition costs, making direct technical measurement increasingly feasible.

1. Jackson, J. A., Mathiassen, S. E. & Liv, P. Observer performance in estimating upper arm elevation angles under ideal viewing conditions when assisted by posture matching software. Appl. Ergon. 55, 208–215 (2016).

2. Jackson, J. A., Mathiassen, S. E., Wahlström, J., Liv, P. & Forsman, M. Is what you see what you get? Standard inclinometry of set upper arm elevation angles. Appl. Ergon. 47, 242–252 (2015).

3. Liv, P., Mathiassen, S. E. & Svendsen, S. W. Theoretical and empirical efficiency of sampling strategies for estimating upper arm elevation. Ann. Occup. Hyg. 55, 436–449 (2011).

4. Liv, P., Mathiassen, S. E. & Svendsen, S. W. Accuracy and precision of variance components in occupational posture recordings: A simulation study of different data collection strategies. BMC Med. Res. Methodol. 12, 58–68 (2012).

5. Rezagholi, M., Mathiassen, S. E. & Liv, P. Cost efficiency comparison of four video-based techniques for assessing upper arm postures. Ergonomics 55, 350–360 (2012).

6. Liv, P., Mathiassen, S. E. & Wahlström, J. Statistical power and measurement requirements in studies comparing observed postures between groups. (PhD Thesis, Umeå University, 2012).

7. Trask, C., Mathiassen, S. E., Rostami, M. & Heiden, M. Observer variability in posture assessment from video recordings: The effect of partly visible periods. Appl. Ergon. 60, 275–281 (2017).

8. Trask, C., Mathiassen, S. E., Jackson, J.A. & Wahlström, J. Data processing costs for three posture assessment methods. BMC Med. Res. Methodol. 13, 124–137 (2013).

9. Waleh Åström, A., Heiden, M., Mathiassen, S. E. & Strömberg, A. Uncertainty in monetary cost estimates for assessing working postures using inclinometry, observation or self-report. in review, (2018).

Background Context

Degenerative changes due to cervical spondylosis (CS) can detrimentally affect work ability and quality of life yet understanding of how physical exposure affects disease progression is limited.PurposeTo assess the associations between occupational physical exposures and occurrence of surgically treated cervical spondylosis (ST-CS) and early exit from the labour market via disability pension.

Study Design/Setting

Prospective register study with 20 year follow-up period.Patient SampleSwedish construction workers participating in a national health surveillance project conducted between 1971-1993.

Outcome Measures

Surgically treated cervical spondylosis (ST-CS) and early labour market exit at a minimum rate of 25% time on disability pension.

Methods

Associations between occupational physical exposures (job exposure matrix) and subsequent ST-CS (National Hospital in-patient register) and early labour market exit via disability pension (Swedish Social Insurance Agency register) were assessed in a cohort of male construction workers (n=237,699).

Results

A total of 1381 ST-CS cases were present and a 20-year incidence rate of 35.1 cases per 100,000 person years (95% confidence interval (CI) 33.2-36.9). Increased relative risk (RR) for ST-CS was found for workers exposed to non-neutral (RR 1.40, 95% CI 1.15-1.69) and awkward neck postures (1.52, 1.19-1.95), working with the hands above shoulder height (1.30, 1.06-1.60), and high upper extremity loading (1.35, 1.15-1.59). Increased risk was also present for workers who reported frequent neck (3.06, 2.18-4.30) and upper back (3.84, 2.57-5.73) pain in the 12 months prior to survey. Among workers with elevated arm exposure, higher risk was seen in those who also had more frequent neck pain. ST-CS cases took early retirement more often (41.3%) and at a younger age (53 years) than the total study cohort (14.8% and 56 years of age, respectively).

Conclusions

Occupational exposure to non-neutral neck postures, work with hands above shoulders and high loads born through the upper extremities increased the risk for ST-CS and early retirement due to disability. Decreasing postural and load exposure is salient for primary, secondary, and tertiary prevention of CS. Neck pain was shown to be a prognostic factor for ST-CS, which stresses the importance of acting early and taking preventative action to reduce workplace exposure, and the need for systematic medical check-ups within primary or occupational care to mitigate disease progression and early labour market exit due to disability.

Background: Normalization of surface electromyography (EMG) is a common and recommended practice, however this methodological step itself introduces variability to a data set. Quantification of this variance is necessary to correctly interpret overall EMG variability. This information is also paramount to identifying experimentally and clinically relevant normalization task(s) which minimize induced variance yet are time-efficient. Purpose: The goal of this study was to quantify the within-day variance of two commonly reported, sub-maximal tasks utilised for low back EMG normalization: one collected with a high degree of meticulousness, and the other collected in a more rapid manner. Results: Only minimal differences were seen between tasks in the magnitude of within-day variance for EMG amplitude at all recording sites, save the right-side L5 location, which showed a significant difference (p=0.020). For trunk posture, within-day variance for the highly meticulous tasks was significantly higher than for the less-meticulous task (p=0.011). Conclusion: A less meticulous sub-maximal normalization task performed in a standing position was equal or superior to a more meticulously collected task in terms of kinematic task repeatability and within-day EMG variance. These findings are encouraging for field study applications where meticulous methods are not feasible, and provide a time saving strategy for lab studies.

Aim: The object of this study was to quantify the contribution of sub-maximal normalisation to the overall variance of exposure parameters describing erector spinae (ES) activity, and to provide guidelines for task selection which minimize methodological variance. Methods: ES EMG was measured from three locations (T9, L1 and L5 levels) on fifteen men performing a manual materials handling task in the laboratory on three separate days. Four repeats of each of eleven sub-maximal normalisation tasks (eight static, three dynamic) were collected, work data were normalised to each task and repeat, and exposure parameters calculated. The unique contribution of normalisation to the overall variance was determined for each task and exposure parameter using variance component analyses. Normalisation tasks were scored according to their relative contributions to the overall variance and coefficients of variation.

Results: A prone task, similar to the Biering-Sørensen test posture, was the most repeatable for all electrode locations and across all exposure parameters. Thoracic level normalisation typically showed poorer repeatability than lumbar normalisation.

Discussion: We recommend that future ES EMG studies employing sub-maximal normalisation utilise said prone task. An alternate normalisation task specific to thoracic level ES muscles may be warranted.

Objectives: To quantify the variance introduced to trapezius electromyography (EMG) through normalization by submaximal reference voluntary exertions (RVE), and to investigate the effect of increased normalization efforts as compared to other changes in data collection strategy on the precision of occupational EMG estimates. Methods: Women performed four RVE contractions followed by 30 minutes of light, cyclic assembly work on each of two days. Work cycle EMG was normalized to each of the RVE trials and seven exposure parameters calculated. The proportions of exposure variance attributable to subject, day within subject, and cycle and normalization trial within day were determined. Using this data, the effect on the precision of the exposure mean of altering the number of subjects, days, cycles and RVEs during data collection was simulated. Results: For all exposure parameters a unique component of variance due to normalization was present, yet small: less than 4.4% of the total variance. The resource allocation simulations indicated that marginal improvements in the precision of a group exposure mean would occur above three RVE repeats for EMG collected on one day, or beyond two RVEs for EMG collected on two or more days.

While electromyography (EM G) is commonly used to quantify levels of muscle activity in different jobs and tasks, less attention has been paid to the size and sources of exposure variability between and within individuals at work. In particular , few attempts have been made to discriminate between biological sources of variabilityand methodological uncertainty, including the effects of the EMG normalization procedure. The present study aimed to quantify the testretest repeatability of reference voluntary effort (R VE) contractions of the upper trapezius and the amount of variance introduced to EMG exposure parameters due to normalization trial variance.

EMG data was collected from the right trapezius muscle of 15 female subjects during 36 work cycles of simulated industrial assembly work on t wo separate days. For all cycles, EMG was norrnalized to each of the four RVE calibration trials collected on the day. From the normalized data the following exposure parameters were calculated for all cycles and norrnalizations: 1 St, 10th, 50th, 90th, and 99th percentile APDF values; mean EMG amplitude; time spent at 'rest' « 6.7% RVE); and time spent at 'large activation levels' (> 100% RVE). Exposure variability due to subjects, day within subject, work cycle within day, and normalization trial was determined using a variance component analysis based on ANOV A algorithms. For all parameters, the dominate source of variance occurred between subjects. For all parameters, except the 1 st APDF percentile and the time spent at rest, the proportions of variance due to norrnalization and cycle were no more than 5% of the sum of all variance components. The betweenday variance for mean and all APDF parameters besides the 1 st APDF percentile ranged from 7 -19% of the total variance, indicating changes in work style or activation patters between days do exist. The effects of normalization reported here are likely at the low end of the range (test-retest coefficient of variation = 0.07) compared to the expected effects when data are collected in the field using less meticulously controIled RVE trials.

Selecting a suitable body posture measurement method requires performance indices of candidate tools. Such data are lacking for observational assessments made at a high degree of resolution. The aim of this study was to determine the performance (bias and between- and within-observer variance) of novice observers estimating upper arm elevation postures assisted by posture matching software to the nearest degree from still images taken under ideal conditions. Estimates were minimally biased from true angles: the mean error across observers was less than 2°. Variance between observers was minimal. Considerable variance within observers, however, underlined the risk of relying on single observations. Observers were more proficient at estimating 0°and 90° postures, and less proficient at 60°. Thus, under ideal visual conditions observers, on average, proved proficient at high resolution posture estimates; further investigation is required to determine how non-optimal image conditions, as would be expected from occupational data, impact proficiency.

European and International sustainable development agendas aim to reduce inequalities in working conditions and work-related health, yet disparate occupational health outcomes are evident between both men and women and domestic- and foreign-born workers. In Sweden, major growth in online retail warehousing has increased occupational opportunities for foreign-born workers. The rapid change has left research lagging on working conditions, i.e., employment conditions, facility design, work organisation, physical and psychosocial work environment conditions, and their effects on worker health. Further, no known studies have considered patterns of inequality related to these factors. The overall aim of this study is to describe working conditions and musculoskeletal health in online retail warehousing, determine the extent to which differences exist related to sex/gender and place of birth (as a proxy for race/ethnicity), and examine factors at the organisational and individual levels to understand why any differences exist.

Three online retail warehouses, each employing 50-150 operations workers performing receiving, order picking, order packing and dispatching tasks will be recruited. Warehouses will, to the extent possible, differ in their extent of digital technology use. Employment conditions, facility design (including digital tool use), work organisation, physical and psychosocial work environment conditions and worker health will be assessed by survey, interview and technical measurements. Analysis of quantitative data stratified by sex and place of birth will consider the extent to which inequalities exist. Focus group interviews with operations employees and in-depth interviews with managers, union and health and safety representatives will be conducted to assess how employee working conditions and musculoskeletal health are related to inequality regimes of sex/gender and/or race/ethnicity in organisational processes and practices in online retail warehousing. The study is pre-registered with the Open Science Framework.

This study will describe working conditions and health in online retail warehouse workers and consider the extent to which patterns of inequality exist based on sex/gender and place of birth.

Background.Increased motor variability while performing repetitive tasks has been suggested to decrease the risk of developing musculoskeletal disorders. However, support for this positive effect is lacking outside of short, simple, highly controlled tasks. It is also currently unknown whether or not existing motor variability metrics are viable for characterising occupational tasks. The purpose of this study was to assess motor variability during a long-cycle simulated occupational task. Using metrics previously validated for short-cycle tasks, this study aimed to determine the extent to which: (1) individuals dif-fered in motor variability with respect to kinematics and/or EMG activation; (2) individual motor variability was consistent across days; and (3) kinematics and EMG motor variability were correlated.

Methods.Following a stringent, three-day training regime, 15 females proved sufficiently proficient to participate. On two occasions, participants performed 36 cycles of an assembly task (combining gross and fine motor skills) at 110 MTM pacing (51 s per cycle). For each cycle, multiple upper arm kinematic and trapezius EMG summary mean and SD variables were calculated; for each variable, the variability across the 36 cycles was assessed. The relative size of variability across individuals, and the consistency of each individual’s motor behaviour across days were assessed using kinematic and EMG vari-ables. The correlation between kinematic and EMG variables was also assessed.

Results.Distinct individual behaviours were observed across days: some participants were clearly more consistent in their motor behaviour than others. Further, a high correlation was found between some kinematic and muscle activation variables.

Discussion. Using previously validated upper arm assessment metrics, we were able to differentiate between individuals performing a long-cycle assembly task based on their degree of motor variability. Given the nature of our study task, we believe the metrics that we found to be successful at identifying individual behaviours could be used for assessing field tasks.

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 un-adjusted 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.

Objectives The aim was to assess the association between occupational biomechanical exposure and the occurrence of radial nerve entrapment (RNE) in construction workers over a 13-year follow-up period. Methods A cohort of 229 707 male construction workers who participated in a national occupational health surveillance programme (1971-1993) was examined prospectively (2001-2013) for RNE. Height, weight, age, smoking status and job title (construction trade) were obtained on health examination. RNE case status was defined by surgical release of RNE, with data from the Swedish national registry for out-patient surgery records. A job exposure matrix was developed, and biomechanical exposure estimates were assigned according to job title. Highly correlated exposures were summed into biomechanical exposure scores. Negative binomial models were used to estimate the relative risks (RR) (incidence rate ratios) of RNE surgical release for the biomechanical factors and exposure sum scores. Predicted incidence was assessed for each exposure score modelled as a continuous variable to assess exposure-response relationships. Results The total incidence rate of surgically treated RNE over the 13-year observation period was 3.53 cases per 100 000 person-years. There were 92 cases with occupational information. Increased risk for RNE was seen in workers with elevated hand-grip forces (RR=1.79, 95% CI 0.97 to 3.28) and exposure to hand-arm vibration (RR=1.47, 95% CI 1.08 to 2.00). Conclusions Occupational exposure to forceful handgrip work and vibration increased the risk for surgical treatment of RNE.

Background: Field studies assessing biomechanical occupational exposures frequently utilize direct observation. PATH (Postures, Activities, Tools, and Handling) is a tool for systematically observing occupational exposures during non-cyclic or long, irregular-cycle jobs. While PATH has been used in many studies, its statistical performance under different data collection strategies has not yet been investigated. The purpose of the current study was to examine this issue. Methods: Data from labourers performing the four tasks comprising a ‘Jacking Pit Construction’ operation was extracted from a previously collected data set. Using a probability based re-sampling bootstrap approach, categorical trunk posture exposure data was compared across nine simulated data collection strategies. Results/Conclusion: At the operational level, dispersion curves showed consistent trends of increased precision with increased sizes of the data set and curves tended to intersect at the expected value seen in the parent data set. At the task level, curves did not always follow the predicted pattern, highlighting the potential pitfalls of using PATH for infrequent tasks and the striking effect that individual workers can have on group exposure estimates of such tasks.

Research suggests an association between motor variability (MV) during repetitive work and work-related musculoskeletal disorders (MSDs). However, whether MV is a consistent individual trait, even across working conditions or tasks, remains unknown. This study assessed whether individual MV traits were consistent during complex work performed under different temporal conditions. Fifteen women performed cyclic assembly under four conditions differing in pace and organisation (line-type, batch-type). MV of trapezius muscle activity and upper arm elevation was quantified and partitioned into variance components. For all MV metrics, a non-zero between-subjects variance was found, indicating consistent individual MV traits across conditions. Variance between subjects was higher for electromyography (EMG) MV metrics compared with kinematic metrics. Our results showed individuals exhibited consistent MV traits across working conditions differing in pace and production process. Further research is needed to understand whether MV is an individual predictive factor for MSD onset or progression.

Introduction: Job rotation is a work organization strategy used to reduce work‐related exposures and musculoskeletal complaints, yet evidence for the efficacy of the approach is weak. Mismatch between job rotation and company needs, lack of full implementation, lack of exposure variation in included tasks, and failure to assess variation may underlie inconclusive research findings to date. The study aims to develop a job rotation with company stakeholders, perform a process evaluation of the implementation, and determine the extent to which the intervention improves the physical and psychosocial work environment, indicators of health, gender and social equality among workers, and production quality and resilience.

Methods and analysis: Approximately 60 production workers at a Swedish commercial laundromat will be recruited. Physical and psychosocial work environment conditions, health, productivity and gender and social equality will be assessed pre‐ and post‐ intervention using surveys, accelerometers, heart rate, electromyography and focus groups. A task‐based exposure matrix will be constructed, and exposure variation estimated at the level of the individual worker pre‐ and post‐ intervention. An implementation process evaluation will be conducted. Job rotation efficacy will be assessed in terms of improvement in work environment conditions, health, gender and social inequality, and production quality and resilience. This study will provide novel information on the effects of the job rotation on physical and psychosocial work environment conditions, production quality and rate, health, and gender and social inequality among blue‐collar workers in a highly multicultural workplace.

Ethics and dissemination: The study received approval from the Swedish Ethical Review Authority. Results of the project will be shared directly with the employees, managers and union representatives from the participating company, other relevant labour market stakeholders, and with researchers at national and international conferences and via scientific publication.

Trial registration: The study is pre‐registered with the Open Science Framework (https://osf.io/zmdc8/).

We evaluated differences in work environment conditions and health by gender and place of birth in a commercial laundromat prior to (baseline) and at the end of the first wave of the COVID-19 pandemic (follow-up). Using survey data, including dimensions from the Copenhagen Psychosocial Questionnaire, from forty-one workers, we assessed work environment conditions and health at baseline, follow-up and in change scores between baseline and follow-up. At baseline, men and women reported similar scores, while foreign-born (FB) workers reported better work environment conditions than Swedish-born (SB) workers. During the pandemic, conditions generally declined for all workers, but FB reported smaller declines than SB. A consistent inequality hierarchy across the 4 groups was not clear at baseline, follow-up or in change scores between time points. The study suggests potential cultural differences may exist in how work environment conditions are experienced. This should be considered in future studies and when managing future crises

Objective. The aim of this study was to assess the association between occupational biomechanical exposures and the occurrence of surgical treatment for subacromial impingement syndrome (SIS).

Methods. A cohort of 220 295 male constructions workers who participated in a national occupational health surveillance program (1971–1993) were examined prospectively over a 16-year follow-up period (2001–2016) for surgically treated SIS. Worker job title, smoking status, height, weight, and age were registered on health examination. Job titles were mapped to 21 occupational groups based on tasks and training. A job exposure matrix (JEM) was developed with exposure estimates for each occupational group. Surgical cases were determined through linkage with the Swedish national in- and outpatient registers. Poisson regression was used to assess the relative risks (RR) for each biomechanical exposure.

Results. The total incidence rate of surgically treated SIS over the 16-year observation period was 201.1 cases per 100 000 person-years. Increased risk was evident for workers exposed to upper-extremity loading (push/pull/lift) (RR 1.45–2.30), high hand grip force (RR 1.47–2.23), using handheld tools (RR 1.52–2.09), frequent work with hands above shoulders (RR 1.62–2.11), static work (RR 1.77–2.26), and hand-arm vibration (RR 1.78–2.13). There was an increased risk for SIS surgery for all occupational groups (construction trades) compared with white-collar workers (RR 1.56–2.61).

Conclusions. Occupational upper-extremity load and posture exposures were associated with increased risk for surgical treatment of SIS, which underlines the need for reducing workplace exposures and early symptom detection in highly exposed occupational groups.

Introduction. Eldercare organizations face high sickness absence rates and staff turnover and rely heavily on temporary workers to fill staffing gaps. Temporary workers may experience differences in job demands and resources compared to permanent workers, but this has been largely understudied.

Aim. To compare perceived job demands and resources between permanent and temporary Swedish eldercare workers.

Methods. Permanent and temporary eldercare workers in a Swedish municipality were invited to answer a digital survey on work environment conditions. Differences between permanent and temporary workers in job demands and resources were analyzed using multivariate analysis of variance adjusted for age, sex, place of birth, and percent of full-time work and univariate analyses were conducted to consider differences in specific factors.

Results. 1076 permanent and 675 temporary workers received the survey and the final study sample included 451 permanent and 151 temporary workers. Multivariate analyses revealed that temporary workers reported statistically significant lower job demands compared to permanent workers, but no statistically significant differences in resources were found between the groups. Univariate analyses showed that temporary workers reported lower quantitative demands, perceived exertion, and time spent bending forward, than permanent workers. These data suggest comparable support across groups, but a higher workload among permanent workers.

Conclusion. Our findings indicate that temporary workers experienced lower job demands than permanent workers, but that no notable difference was found in resources. Interventions aimed at distributing job demands more evenly among eldercare workers with different employment forms may be necessary.

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 re-sampling 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- and task-levels and, for each of these, 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- 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.

Objectives. Studies in the goods supply chain in areas outside of warehousing show evidence of gender and racial/ethnic inequalities in working conditions (i.e., in work organization, work environment and employment conditions). This review aimed to identify, summarize, and discuss research focused on inequality in warehousing and its effects on warehouse working conditions. In the review, racial/ethnic inequality includes inequality related to country of birth and (im)migration status.

Methods. We performed a systematic search in the Scopus and Web of Science databases to identify warehouse studies that addressed working conditions and (in)equality at a workplace level. Screening of records was performed using the Rayyan systematic review tool. Risk of bias was assessed according to established methods and checklists. 

Results. Database searches yielded 4910 articles. After title-abstract-keyword and full-text screenings, 21articles were included. Results showed inequality based on gender and race/ethnicity in both work organization (different tasks were performed by different groups of employees), work environment conditions (physical and psychosocial aspects differed) and employment conditions (disparate employment types and incomes between groups of employees). Health differences, as a possible result of unequal working conditions, were evident between different racial/ethnic groups of employees. A hierarchy that included both gender and race/ethnicity was found, with (im)migrant and racialized women positioned at the bottom.

Conclusions. We found evidence that gender and race/ethnicity influenced work organization, work environment conditions, and employment conditions. Evidence was found for an intersection between gender and race/ethnicity. To improve working conditions, and subsequently occupational health, we encourage researchers to simultaneously consider gender and race/ethnicity factors at work, and to consider both why inequality is present and how it impacts working conditions in future studies of warehousing, particularly in online retailing.

Objectives. Data processing contributes a non-trivial proportion to total research costs, but documentation of these costs is rare. This paper employed a priori cost tracking for three posture assessment methods (self-report, observation of video, and inclinometry), developed a model describing the fixed and variable cost components, and simulated additional study scenarios to demonstrate the utility of the model. 

Methods. Trunk and shoulder postures of aircraft baggage handlers were assessed for 80 working days using all three methods. A model was developed to estimate data processing phase costs, including fixed and variable components related to study planning and administration, custom software development, training of analysts, and processing time.   

Results. Observation of video was the most costly data processing method with total cost of € 31,433, and was 1.2-fold more costly than inclinometry (€ 26,255), and 2.5-fold more costly than self-reported data (€ 12,491). Simulated scenarios showed altering design strategy could substantially impact processing costs. This was shown for both fixed parameters, such as software development and training costs, and variable parameters, such as the number of work-shift files processed, as well as the sampling frequency for video observation.  When data collection and data processing costs were combined, the cost difference between video and inclinometer methods was reduced to 7%; simulated data showed this difference could be diminished and, even, reversed at larger study sample sizes. Self-report remained substantially less costly under all design strategies, but produced alternate exposure metrics. 

Conclusions. These findings build on the previously published data collection phase cost model by reporting costs for post-collection data processing of the same data set.  Together, these models permit empirically based study planning and identification of cost-efficient study designs.

This review is an update of a previous systematic review and assesses the evidence for the association of work-related physical and psychosocial risk factors and specific disorders of the shoulders. Medline, Embase, Web of Science Core Collection, Cochrane Central and PsycINFO were searched and study eligibility and risk of bias assessment was performed by two independent reviewers. A total of 14 new articles were added with the majority focusing on rotator cuff syndrome (RCS) with seven studies. Nine articles reported psychosocial exposures in addition to physical exposures. The strongest evidence was found for the association between elevation, repetition, force and vibration and the occurrence of SIS and tendinosis/tendonitis. Evidence also suggests that psychosocial exposures are associated with the occurrence of RCS and tendinosis/tendonitis. Other findings were inconsistent which prevents drawing strong conclusions.

Objectives: The present study assessed full shift trunk and upper arm postural exposure amplitudes, frequencies, and durations among Swedish airport baggage handlers, and aimed to determine whether exposures differ between workers at the ramp (loading and unloading aircraft) and baggage sorting areas.

Methods: Trunk and upper arm postures were measured using inclinometers during three full work shifts on each of 27, male baggage handlers working at a large Swedish airport. Sixteen of the baggage handlers worked on the ramp and 11 in the sorting area. Variables summarizing postures and movements were calculated, and mean values and variance components between subjects and within subject (between days) were estimated using restricted maximum likelihood algorithms in a one-way random effect model.

Results: In total, data from 79 full shifts (651 hours) were collected with a mean recording time of 495 minutes per shift (range 319-632). On average, baggage handlers worked with the right and left arm elevated >60° for 6.4% and 6.3% of the total workday, respectively. The 90^th percentile trunk forward projection (FP) was 34.1° and the 50^th percentile trunk movement velocity was 8°s^-1. For most trunk (FP) and upper arm exposure variables, between-subject variability was considerable, suggesting that the flight baggage handlers were not a homogeneously exposed group. A notable between-days variability pointed to the contents of the job differing on different days. Peak exposures (>90°) were higher for ramp workers than for sorting area workers (trunk 0.6% ramp vs 0.3% sorting; right arm 1.3% ramp vs 0.7% sorting).

Conclusions: Trunk and upper arm postures and movements among flight baggage handlers measured by inclinometry were similar to those found in other jobs comprising manual material handling, known to be associated with increased risks for musculoskeletal disorders. The results showed that full-shift trunk (FP), and to some extent peak arm exposures, were higher for ramp workers compared to sorting workers.