Self-assessed and directly measured occupational physical activities--influence of musculoskeletal complaints, age and gender

Consistency between the ACGIH TLV for hand activity and proposed action levels for wrist velocity and forearm muscular load based on objective measurements: an example from the assembly industry

Objectives. This study aimed to investigate the consistency between results of the American Conference for Governmental Occupational Hygienists (ACGIH) threshold limit value (TLV) for hand activity and proposed action levels of objective measurements in risk assessments of work-related musculoskeletal disorders. Methods. Wrist velocities and forearm muscular load were measured for 11 assemblers during one working day. Simultaneously, each assembler's hand activity level (HAL) during three sub-cycles was rated twice on two separate occasions by two experts, using a HAL scale. Arm/hand exertion was also rated by the assemblers themselves using a Borg scale. In total, 66 sub-cycles were assessed and assigned to three exposure categories: A) below ACGIH action limit (AL) (green); B) between AL and TLV (yellow); and C) above TLV (red). The median wrist velocity and the 90th percentile of forearm muscular load obtained from the objective measurements corresponding to the sub-cycles were calculated and assigned to two exposure categories: A) below or C) above the proposed action level. Results. The agreement between ACGIH TLV for hand activity and the proposed action level for wrist velocity was 87%. Conclusions. The proposed action level for wrist velocity is highly consistent with the TLV. Additional studies are needed to confirm the results.

Impact of Fatigue on Ergonomic Risk Scores and Foot Kinetics: A Field Study Employing Inertial and In-Shoe Plantar Pressure Measurement Devices

(1) Background: Occupational fatigue is a primary factor leading to work-related musculoskeletal disorders (WRMSDs). Kinematic and kinetic experimental studies have been able to identify indicators of WRMSD, but research addressing real-world workplace scenarios is lacking. Hence, the authors of this study aimed to assess the influence of physical strain on the Borg CR-10 body map, ergonomic risk scores, and foot pressure in a real-world setting. (2) Methods: Twenty-four participants (seventeen men and seven women) were included in this field study. Inertial measurement units (IMUs) (n = 24) and in-shoe plantar pressure measurements (n = 18) captured the workload of production and office workers at the beginning of their work shift and three hours later, working without any break. In addition to the two 12 min motion capture processes, a Borg CR-10 body map and fatigue visual analog scale (VAS) were applied twice. Kinematic and kinetic data were processed using MATLAB and SPSS software, resulting in scores representing the relative distribution of the Rapid Upper Limb Assessment (RULA) and Computer-Assisted Recording and Long-Term Analysis of Musculoskeletal Load (CUELA), and in-shoe plantar pressure. (3) Results: Significant differences were observed between the two measurement times of physical exertion and fatigue, but not for ergonomic risk scores. Contrary to the hypothesis of the authors, there were no significant differences between the in-shoe plantar pressures. Significant differences were observed between the dominant and non-dominant sides for all kinetic variables. (4) Conclusions: The posture scores of RULA and CUELA and in-shoe plantar pressure side differences were a valuable basis for adapting one-sided requirements in the work process of the workers. Traditional observational methods must be adapted more sensitively to detect kinematic deviations at work. The results of this field study enhance our knowledge about the use and benefits of sensors for ergonomic risk assessments and interventions.

Physiological responses, trunk posture, and work pace in commercial building cleaning in Washington State: An observational field study

INTRODUCTION

This study aimed to investigate whether work pace is a critical indicator for predicting a janitor's risk of work-related musculoskeletal disorders (WMSDs).

METHOD

Field measurements were obtained from commercial building janitors as well as the determination of work pace. Physiological responses collected were heart rate, energy expenditure (calories), activity level (METs), steps, trunk posture. Data were obtained using direct measurements, along with a time study, which was performed by shadowing 13 janitors in Washington State. The measured values were summarized descriptively, and five of the most common janitorial tasks were compared. The relationships between work pace and the physiological response variables were determined by calculating the Pearson product-moment correlation coefficients.

RESULTS

The highest average percent heart rate reserve (47.4%) was reported during restroom cleaning, while the highest activity and energy expenditure levels (3.6 METs and 217.1 calories/h) were reported for mopping. The top 90% of trunk flexion angles and the highest percentage of time in trunk flexion from 20° to 60° were recorded during restroom cleaning. Restroom cleaning showed the highest correlation between all the physiological response variables and work pace. In most of the tasks, a high work pace may have increased the degree and duration of severe trunk flexion.

CONCLUSION

Overall, when several tasks were considered, the extent of physiological responses, trunk joint angles, and exposure time to awkward postures tended to increase with an increase in work pace.

PRACTICAL APPLICATIONS

This study showed the feasibility of using the work pace measured from time studies as a predictive indicator of WMSDs risks. Using this information, managers may compose a schedule that can minimize WMSDs risks while considering actual work pace deviations that may impact a janitor's ability to complete assigned tasks properly within a shift.

Association of vocational interventions and work-related factors with disease and work outcomes in people with RMDs: A systematic review

OBJECTIVE

A EULAR taskforce was convened to develop recommendations for lifestyle behaviours amongst people with rheumatic and musculoskeletal diseases (RMDs). This paper reviews the literature on work-related factors and disease-specific outcomes for people with osteoarthritis, rheumatoid arthritis (RA), systemic lupus erythematosus, axial spondyloarthritis (axSpA), psoriatic arthritis, systemic sclerosis (SSc) and gout.

METHODS

Two separate systematic literature reviews (SLRs) were conducted. The first identified SLRs, published between 01/2013 and 09/2018. The second identified original observational and intervention studies published before 05/2019. Manuscripts were included if they assessed the effects of vocational interventions on disease-specific outcomes (i.e. clinical outcomes, patient-reported outcomes, and work outcomes) or if they assessed the association between work-related factors and these outcomes. Medline, Embase, Cochrane Library of systematic reviews and CENTRAL databases were searched.

RESULTS

Two SLRs were identified including individuals with SSc and inflammatory arthritis. Subsequently, 23 original manuscripts were identified, with most of them (43.5%) including people with RA and no manuscripts on gout. Most observational studies evaluated the association between work-related factors and work outcomes while limited information was available on the impact of work on clinical outcomes. A few studies suggested that physically demanding jobs have a small detrimental effect on radiographic progression in axSpA and PsA. Intervention studies showed beneficial effects of vocational interventions for disease-specific outcomes, but with small effect sizes.

CONCLUSION

Many studies indicated that work participation is not likely to be detrimental and, in some cases, may be beneficial for RMD-specific outcomes and should therefore receive attention within healthcare consultations.

The problem with "ergonomics injuries": What can ergonomists do?

Effects of psychosocial hazards on risk of musculoskeletal disorders (MSDs) are often very substantial, but workplace risk management practices focus largely on biomechanical hazards, as do the risk assessment methods used by ergonomists. Translation of research evidence into more effective workplace practices demands a more holistic risk management framework that encompasses both types of hazard. In this context, we evaluate the validity of different MSD risk assessment methods for different purposes, focusing particularly on requirements for routine workplace risk management. These include choice of fit-for-purpose assessment methods, prioritisation of hazards that are most affecting risk, and control actions as high as possible in the risk control hierarchy. Ergonomists could facilitate more effective workplace risk management by promoting: awareness of the need for change; improvements to guidance from OHS regulators; research on MSD-related workplace management issues; and professional development programs on this topic for ergonomists and other OHS practitioners.

Assessing physical workload among people with musculoskeletal disorders: validity and reliability of the physical workload questionnaire

Background

Demands of physical work are related to musculoskeletal disorders, and hence, important to assess. The Physical Workload Questionnaire (PWQ) is based on 26 items related to physical workload. The PWQ has been translated into Norwegian, but its psychometric properties have not yet been tested. The aim of this study was to assess the validity and reliability of the PWQ among patients with musculoskeletal disorders.

Methods

A cross-sectional study with a test-retest design was conducted to assess construct validity (structural validity and hypothesis testing) and reliability (internal consistency and test-retest reliability) among employed patients with musculoskeletal disorders. Exploratory factor analysis was performed to assess the structural validity and number of items to be included in the Norwegian version of the PWQ. Hypothesis testing was assessed by 14 a priori hypotheses (“known” group, convergent and discriminant validity). Internal consistency was evaluated using Cronbach’s alpha and test-retest reliability by Intraclass Correlation Coefficient (ICC_2.1), Standard Error of Measurement (SEM_agreement) and Smallest Detectable Change (SDC_95%ind).

Results

In total, 115 patients with a mean age (SD) of 46 (9) years were included, of which 48 were included in the reliability analyses. Exploratory factor analysis resulted in two subscales: “Heavy physical work” (15 items, range 0–100) and “Long-lasting postures and repetitive movements” (7 items, range 0–100). No floor or ceiling effects were seen in the subscales. Twelve of the 14 (85%) predefined hypotheses were confirmed. The internal consistency with Cronbach’s alpha was 0.94 and 0.85 on subscales 1 and 2, respectively. Test-retest reliability analyses demonstrated an ICC_2.1 of 0.96 (95% CI 0.88, 0.98) and 0.92 (95% CI 0.81, 0.96), SEM of 6.9 and 10.0 and SDC_95%ind of 19.2 and 27.7 of subscales 1 and 2, respectively.

Conclusions

The Norwegian version of the PWQ demonstrated good validity and reliability and can be used to evaluate physical workload in patients with musculoskeletal disorders.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05222-y.

An Exploratory Study on the Physical Activity Health Paradox-Musculoskeletal Pain and Cardiovascular Load during Work and Leisure in Construction and Healthcare Workers

Using a novel approach, this exploratory study investigated whether the physical activity (PA) paradox extends to cardiovascular load and musculoskeletal pain. At baseline, 1–2 days of 24 h heart rate was assessed in 72 workers from construction and healthcare. Workers then reported pain intensity in 9 body regions (scale 0–3) every 6 months for two years. The 2 year average of musculoskeletal pain (sum of 9 pain scores; scale 0–27) was regressed on time spent during work and leisure above three thresholds of percentage heart rate reserve (%HRR), i.e., ≥20 %HRR, ≥30 %HRR, and ≥40 %HRR, using a novel ilr structure in compositional data analysis. Analyses were stratified for several important variables. Workers spending more time in physical activity at work had higher pain, while workers with more time in physical activity during leisure had less pain (i.e., the PA paradox), but none of the associations were statistically significant. Higher aerobic capacity and lower body mass index lowered the pain score among those with higher physical activity at work. This exploratory study suggests that the PA paradox may apply to musculoskeletal pain and future studies with larger sample sizes and additional exposure analyses are needed to explain why this occurs.

Early Occupational Intervention for People with Low Back Pain in Physically Demanding Jobs: 1-year Follow-up Results of the Randomized Controlled GOBACK Trial

STUDY DESIGN

Randomized controlled trial with 1-year follow up.

OBJECTIVE

The aim of this study was to assess whether people with low back pain (LBP) and self-reported physically demanding jobs, benefit from an occupational medicine intervention, in addition to a single hospital consultation and a magnetic resonance imaging, at 1 year of follow-up. Secondly, to examine whether the positive health effects, found in both groups at 6 months, persist at 1-year follow-up.

SUMMARY OF BACKGROUND DATA

The prevalence of LBP is high in the working population, resulting in a substantial social and economic burden. Although there are many guidelines available on the management of LBP, including multidisciplinary biopsychosocial rehabilitation, they provide limited guidance on the occupational medicine aspects.

METHODS

As reported previously, 305 participants with LBP and self-reported physically demanding jobs were enrolled in the randomized controlled study and randomly allocated to clinical care with additional occupational medicine intervention or clinical care alone. Data were collected at baseline, 6 months, and 1 year. Outcomes included in the present 1-year follow-up study are changes in neuropathic pain (painDETECT questionnaire), severity of pain (0-10 numerical rating scale), disability (Roland Morris Disability Questionnaire), fear-avoidance beliefs (FABQ), physical, and mental quality of life (short-form 36).

RESULTS

The study showed no effect of an occupational intervention on neuropathic pain, fear-avoidance beliefs, physical and mental quality of life nor disability measured after 1 year. The positive effects found at 6 months in both groups, remained at 1-year follow-up.

CONCLUSION

The results suggest that a thorough clinical consultation, with focus on explaining the cause of pain and instructions to stay active, can promote long-lasting physical and mental health in individuals with LBP. Therefore, additional occupational interventions could focus on altering occupational obstacles on a structural level.Level of Evidence: 2.

Differences between risk situations identified using a self-reported questionnaire and an observational method

BACKGROUND

This study investigates work-related musculoskeletal disorders risk estimation by frequently as used as ergonomic methods in the field.

OBJECTIVE

To identify the difference in risk estimation by an in-house observational method and a self-reported questionnaire, and to evaluate the complementary aspects of these methods.

METHODS

A sample of 15 operators who worked on the assembly workstations was selected from a truck manufacturing plant. The risk assessment of these workstations (28 scenarios) was performed by the observational method and the self-reported questionnaire. The agreement between both methods to identify risk situations was measured with the weighted Kappa coefficient.

RESULTS

The observational method and the self-reported questionnaire deployed on the same activity estimated different risk situations.

CONCLUSION

This analysis does not reveal that one tool is more powerful than the other one, but shows the probability of different risk estimation. The complementary effect of each method might be considered for further investigation concerning musculoskeletal risk factors.

Elbow tendinopathy and occupational biomechanical overload: A systematic review with best-evidence synthesis

OBJECTIVES

To evaluate the evidence of an association between occupational and non-occupational exposure to biomechanical risk factors and lateral elbow tendinopathy, medial elbow tendinopathy, and olecranon bursitis.

METHODS

We carried out a systematic review of the literature. We searched MEDLINE (up to November 2019) and checked the reference lists of relevant articles/reviews. We aimed to include studies where (a) the diagnosis was based on physical examination (symptoms plus clinical signs) and imaging data (if any); and (b) the exposure was evaluated with video analysis and/or direct measurements. A quality assessment of the included studies was performed along with an evaluation of the level of evidence of a causal relationship.

RESULTS

We included four studies in the qualitative synthesis: two prospective cohorts and two cross-sectional studies. All the included studies investigated "lateral/medial epicondylitis", albeit the diagnosis was not supported by imaging techniques. Two cohort studies suggested that a combination of biomechanical risk factors for wrist/forearm is associated with increased risk of "lateral epicondylitis". This association was not observed in the two included cross-sectional studies. The cohort studies suggested that a Strain Index score higher than 5 or 6.1 could double the risk of "lateral epicondylitis". No association with increased risk of "medial epicondylitis" was observed.

CONCLUSIONS

There is limited evidence of a causal relationship between occupational exposure to biomechanical risk factors and lateral elbow tendinopathy. For medial elbow tendinopathy, the evidence is insufficient to support this causal relationship. No studies on olecranon bursitis and biomechanical overload were identified.

Quantification of Exposure to Risk Postures in Truck Assembly Operators: Neck, Back, Arms and Wrists

The study assessed the proportion of time in risky postures for the main joints of the upper limbs in a truck assembly plant and explored the association with musculoskeletal symptoms. Fourteen workstations (13 individuals) of a truck assembly plant were selected, and seven sensors were placed on the body segments of the participants. The sensors included tri-axial accelerometers for the arms and back, inclinometers for the neck and electro-goniometry for quantifying flexion/extension of the right and left hands. The proportions of time in moderate awkward postures were high at all workstations. Neck and wrist excessive awkward postures were observed for most workstations. The average values of the 91st percentile for back flexion and right/left arm elevation were 25°, 62°, and 57°, respectively. The 91st and 9th percentile averages for neck flexion/extension were 35.9° and −4.7°, respectively. An insignificant relationship was found between the percentage of time spent in awkward upper limb posture and musculoskeletal symptoms. The findings provide objective and quantitative data about time exposure, variability, and potential risk factors in the real workplace. Quantitative measurements in the field provide objective data of the body postures and movements of tasks that can be helpful in the musculoskeletal disorders (MSDs) prevention program.

Comparison Between a Job-Exposure Matrix (JEM) Score and Self-Reported Exposures for Carrying Heavy Loads Over the Working Lifetime in the CONSTANCES Cohort

OBJECTIVES

Job-exposure matrices (JEMs) were developed to allow assessment of past work exposure for large population-based studies where better exposures data are unavailable. Few studies have directly compared biomechanical JEMs to self-administered questionnaires. We compared assessments of cumulative exposure to carrying heavy loads based on 'JEM Constances' to individually self-reported (SR) exposures.

METHODS

In the French CONSTANCES cohort at inception, past SR exposure to carrying heavy loads (ever/never and durations) and a detailed job history were available for 26 929 subjects. JEM Constances, an existing biomechanical JEM based on SR current exposures from 26 821 asymptomatic workers, was combined with job history to build a cumulative biomechanical exposure score. Using individual SR exposure as the reference, Area Under the Curve (AUC) of Receiver Operating Characteristic (ROC) curves, sensitivity, and specificity were calculated. For both methods, associations with low back pain and knee pain were computed using multinomial logistic models. Additional analyses compared older (>10 years) to more recent (≤10 years) exposures.

RESULTS

AUCs ranged from 0.795 (0.789-0.800) when all periods were considered, to 0.826 (0.820-0.833) for more recent biomechanical exposure (≤10 years). Associations between carrying heavy loads and low back pain or knee pain were less strong using JEM assessment than individually SR exposure: for low back pain ORSR = 3.02 (2.79-3.26) versus ORJEM = 1.70 (1.59-1.82) and for knee pain ORSR = 2.27 (2.10-2.46) versus ORJEM = 1.64 (1.53-1.77).

CONCLUSIONS

JEM Constances' assessment of cumulative exposure of carrying heavy loads seems to be a useful method compared to a self-administrated questionnaire for large population-based studies where other methods are not available.

Neck and upper extremity pain in sonographers - a longitudinal study

Background

Sonographers have reported a high occurrence of musculoskeletal pain for more than 25 years. Assessments of occupational risk factors have previously been based on cross-sectional surveys. The aim of this longitudinal study was to determine which factors at baseline that were associated with neck/shoulder and elbow/hand pain at follow-up.

Methods

A questionnaire was answered by 248 female sonographers at baseline and follow-up (85% of the original cohort). 208 were included in the analyses. Physical, visual, and psychosocial work-related conditions were assessed at baseline. Pain in two body regions (neck/shoulders and elbows/hands) was assessed at both baseline and follow up.

Results

Pain at baseline showed the strongest association with pain at follow-up in both body regions [prevalence ratio (PR) 2.04; 95% confidence interval (CI) 1.50–2.76], for neck/shoulders and (PR 3.45; CI 2.29–5.22) for elbows/hands. Neck/shoulder pain at follow-up was associated with inability of ergonomic adjustments at the ultrasound device (PR 1.25; CI 1.05–1.49), a high mechanical exposure index (PR 1.66; CI 1.09–2.52), and adverse visual conditions (PR 1.24; CI 1.00–1.54) at baseline. Moreover, among participants with no neck/shoulder pain at baseline, high job demands (PR 1.78; CI 1.01–3.12), and a high mechanical exposure index (PR 2.0; CI 0.98–4.14) predicted pain at follow-up. Pain in the elbows/hands at follow-up was associated with high sensory demands at baseline (PR 1.63; CI 1.08–2.45), and among participants without pain at baseline high sensory demands predicted elbow/hand pain at follow-up (PR 3.34; CI 1.53–7.31).

Conclusion

Pain at baseline was the strongest predictor for pain at follow-up in both body regions. We also found several occupational factors at baseline that were associated with pain at follow-up: inability to adjust equipment, adverse visual conditions, a high MEI, high job demands and high sensory demands. These results point at a possibility to influence pain with better ergonomics.

Factors associated with non-specific low back pain in children aged 10-12 from Bucaramanga, Colombia: A cross-sectional study

BACKGROUND

There are no Colombian studies published that assess non-specific low back pain (NSLBP) risk factors in children.

OBJECTIVE

To determine the factors associated with NSLBP in 73 children (19.2% girls) aged 10-12 years in one military school in Bucaramanga, Colombia.

METHODS

A questionnaire was used to obtain information of risk factors. Subsequently, children's weight and height were measured. The backpack was weighed at the beginning of each day from Monday to Friday. Crude and adjusted prevalence ratios were calculated, with their respective 95% confidence interval (CI).

RESULTS

The one-month prevalence of NSLBP was 39.7% (95% CI 28.4-51.9). In the multivariate analysis, carrying backpacks wearing between 12% and 20% of body weight, having a perception that the backpack is very heavy, and being a passive smoker increase the likelihood of NSLBP, while being 11-year-old compared to 10-year-old decreases the likelihood of having NSLBP, adjusted for gender, body mass index, and history of LBP in parents.

CONCLUSIONS

High prevalence of low back pain was found in children between 10 and 12 years old. The study of the decisive factors of low back pain is important to identify children at risk, as well as to develop efficient primary prevention programs.

Objectively measured occupational physical activity in blue-collar workers: What is the role of job type, gender and psychosocial resources?

The aim was to describe occupational physical activity (OPA) and examine the role of psychosocial job resources among blue-collar workers. In a sample of 198 workers (57% male; mean age 44.9 (SD 9.9) year) from 7 companies in Denmark, two accelerometers (Actigraph) were placed on the thigh and trunk during 1-5 consecutive days, to determine working time spent standing, walking, on feet and in activity of moderate to vigorous intensity level (MVPA). The level of influence and social support at work were assessed by questionnaire. The exposure to OPA significantly varied by particular job type, especially in male predominant occupations. Overall, psychosocial job resources did not affect the exposure to OPA. These findings suggest that workplace interventions aiming to prevent adverse outcomes of OPA among blue-collars workers ought to focus on task redesign and target work organizational factors related to specific job type.

Validity of simplified, calibration-less exercise intensity measurement using resting heart rate during sleep: a method-comparison study with respiratory gas analysis

Background

The recent development of wearable devices has enabled easy and continuous measurement of heart rate (HR). Exercise intensity can be calculated from HR with indices such as percent HR reserve (%HRR); however, this requires an accurate measurement of resting HR, which can be time-consuming. The use of HR during sleep may be a substitute that considers the calibration-less measurement of %HRR. This study examined the validity of %HRR on resting HR during sleep in comparison to percent oxygen consumption reserve (%VO₂R) as a gold standard. Additionally, a 24/7%HRR measurement using this method is demonstrated.

Methods

Twelve healthy adults aged 29 ± 5 years underwent treadmill testing using the Bruce protocol and a 6-min walk test (6MWT). The %VO₂R during each test was calculated according to a standard protocol. The %HRR during each exercise test was calculated either from resting HR in a sitting position (%HRR_sitting), when lying awake (%HRR_lying), or during sleep (%HRR_sleeping). Differences between %VO₂R and %HRR values were examined using Bland-Altman plots. A 180-day, 24/7%HRR measurement with three healthy adults was also conducted. The %HRR values during working days and holidays were compared.

Results

In the treadmill testing, the mean difference between %VO₂R and %HRR_sleeping was 1.7% (95% confidence interval [CI], − 0.2 to 3.6%). The %HRR_sitting and %HRR_lying values were 10.8% (95% CI, 8.8 to 12.7%) and 7.7% (95% CI, 5.4 to 9.9%), respectively. In the 6MWT, mean differences between %VO₂R and %HRR_sitting, %HRR_lying and %HRR_sleeping were 12.7% (95% CI, 10.0 to 15.5%), 7.0% (95% CI, 4.0 to 10.0%) and − 2.9% (95% CI, − 5.0% to − 0.7%), respectively. The 180-day, 24/7%HRR measurement presented significant differences in %HRR patterns between working days and holidays in all three participants.

Conclusions

The results suggest %HRR_sleeping is valid in comparison to %VO₂R. The results may encourage a calibration-less, 24/7 measurement model of exercise intensity using wearable devices.

Trial registration

UMIN000034967.

Registered 21 November 2018 (retrospectively registered).

Physical demand at work and sick leave due to low back pain: a cross-sectional study

OBJECTIVES

To investigate if self-reported high physical demand at work, objective physical workload using a job exposure matrix (JEM) and fear-avoidance beliefs are associated with reported sick leave in the previous year in persons with low back pain (LBP). Second, to investigate if the effects of fear-avoidance and self-reported high physical demand at work on sick leave are modified by the objective physical workloads.

SETTINGS

Participants were recruited from general practice and by advertisement in a local newspaper.

PARTICIPANTS

305participants with a current period of 2-4 weeks LBP and self-reported difficulty in maintaining physically demanding jobs due to LBP were interviewed, clinically examined and had an MRI at baseline.

MAIN OUTCOME MEASURES

Independent variables were high fear-avoidance, self-reported high physical demand at work and objective measures of physical workloads (JEM). Outcome was self-reported sick leave due to LBP in the previous year. Logistic regression and tests for interaction were used to identify risk factors and modifiers for the association with self-reported sick leave.

RESULTS

Self-reported physically demanding work and high fear-avoidance were significantly associated with prior sick leave due to LBP in the previous year with OR 1.75 95% CI (1.10 to 2.75) and 2.75 95% CI (1.61to 4.84), respectively. No objective physical workloads had significant associations. There was no modifying effect of objective physical workloads on the association between self-reported physical demand at work/high fear-avoidance and sick leave.

CONCLUSIONS

Occupational interventions to reduce sick leave due to LBP may have to focus more on those with high self-reported physical demands and high fear-avoidance, and less on individuals with the objectively highest physical workload.

TRIAL REGISTRATION NUMBER

NCT02015572; Post-results.

Physical workload and obesity have a synergistic effect on work ability among construction workers

PURPOSE

Obesity and high physical workload are both associated with poor work ability, but the interaction between obesity and high physical workload on work ability is not yet fully understood. Obesity and high physical workload may share a common mechanical pathway, possibly leading to a synergistic negative effect on work ability. The purpose of this study was to investigate the effect of obesity on work ability in workers with high versus low physical work load.

METHODS

A longitudinal study was conducted among 36,435 Dutch construction workers who participated in at least two periodic medical examinations during the years 2008-2015. Logistic regression analyses were used to investigate the effect of manual material handling and strenuous work postures in sports on the association between obesity and work ability. Work ability was measured using the self-reported Work Ability Index consisting of seven dimensions. Confounding effects were tested for age, educational level, smoking, vigorous physical activity, psychosocial work demands, and working hours. Additive interaction between obesity and physical workload on work ability was tested using the relative excess risk due to interaction (RERI).

RESULTS

Construction workers with overweight (OR = 1.09; 95% CI 1.02-1.16) or obesity (OR = 1.27; 95% CI 1.17-1.38) had an increased risk of poor/moderate work ability. Exposure to manual material handling (OR = 1.58; 95% CI 1.49-1.68) or strenuous work postures (OR = 1.80; 95% CI 1.70-1.90) also increased the risk of poor/moderate work ability. The effect of the combination of obesity with high physical workload was greater than the sum of the individual effects (strenuous work postures: RERI = 0.39; 95% CI 0.10-0.67; manual material handling: RERI = 0.26; 95% CI 0.02-0.51).

CONCLUSIONS

Obesity and high physical workload were associated with poor work ability and had a synergistic, negative effect on work ability. Interventions that prevent obesity and high physical workload might have a beneficial effect on work ability.

Device-measured physical activity, sedentary behaviour and cardiometabolic health and fitness across occupational groups: a systematic review and meta-analysis

BACKGROUND

With approximately 8 hours of one's waking day spent at work, occupational tasks and environments are important influencers on an individual's physical activity (PA) and sedentary behaviours. Little research has compared device-measured physical activity, sedentary behaviour and cardiometabolic outcomes between occupational groups.

OBJECTIVE

To compare device-measured movement (sedentary time [ST], light intensity physical activity [LPA], moderate-to-vigorous intensity physical activity [MVPA], and steps) across occupations. The secondary objective was to examine whether cardiometabolic and fitness outcomes differed by occupation.

METHODS

Five bibliographic databases were searched to identify all studies which included working age, employed adults from high-income countries, and reported on device-measured movement within occupations. Risk of bias within and across studies was assessed. Results were synthesized using meta-analyses and narrative syntheses.

RESULTS

The review includes 132 unique studies with data from 15,619 participants. Working adults spent ~ 60% of their working and waking time engaged in sedentary behaviour; a very small proportion (~ 4%) of the day included MVPA. On average, workers accumulated 8124 steps/day. Office and call center workers' steps/day were among the lowest, while those of postal delivery workers were highest. Office workers had the greatest ST and the lowest time in LPA both at work and during wakeful time. However, office workers had the greatest minutes sent in MVPA during wakeful hours. Laborers had the lowest ST and spent a significantly greater proportion of their work time in LPA and MVPA. Healthcare and protective services workers had higher levels of LPA at work compared to other occupations. Workers in driving-based occupations tended to have a higher body mass index and blood pressure.

CONCLUSION

This review identifies that occupational and wakeful time PA and ST differed between occupations. Future studies are needed to assess whether patterns differ by age and sex, describe leisure-time movement and movement patterns, and the relationship with cardiometabolic health.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42017070448 .

The CONSTANCES job exposure matrix based on self-reported exposure to physical risk factors: development and evaluation

Objectives

Job exposure matrices (JEMs) can be constructed from expert-rated assessments, direct measurement and self-reports. This paper describes the construction of a general population JEM based on self-reported physical exposures, its ability to create homogeneous exposure groups (HEG) and the use of different exposure metrics to express job-level estimates.

Methods

The JEM was constructed from physical exposure data obtained from the Cohorte des consultants des Centres d’examens de santé (CONSTANCES). Using data from 35 526 eligible participants, the JEM consisted of 27 physical risk factors from 407 job codes. We determined whether the JEM created HEG by performing non-parametric multivariate analysis of variance (NPMANOVA). We compared three exposure metrics (mean, bias-corrected mean, median) by calculating within-job and between-job variances, and by residual plots between each metric and individual reported exposure.

Results

NPMANOVA showed significantly higher between-job than within-job variance among the 27 risk factors (F(253,21964)=61.33, p<0.0001, r²=41.1%). The bias-corrected mean produced more favourable HEG as we observed higher between-job variance and more explained variance than either means or medians. When compared with individual reported exposures, the bias-corrected mean led to near-zero mean differences and lower variance than other exposure metrics.

Conclusions

CONSTANCES JEM using self-reported data yielded HEGs, and can thus classify individual participants based on job title. The bias-corrected mean metric may better reflect the shape of the underlying exposure distribution. This JEM opens new possibilities for using unbiased exposure estimates to study the effects of workplace physical exposures on a variety of health conditions within a large general population study.

The association between awkward working posture and low back disorders in farmers: a systematic review

BACKGROUND

Low back disorders (LBD) are the most common musculoskeletal problem among farmers, with higher prevalence than other occupations. Although studies of the general population have shown an association between LBD and awkward working posture, farmers have unique work context and exposures that may modify this relationship. This review aimed to 1) identify published research studies investigating posture as a risk factor for LBD in farmers/agricultural workers, and 2) determine the strength of the relationship between postural exposure and LBD risk of bias assessment.

METHOD

Comprehensive electronic searches of Medline, Web of Science, CINAHL, SCOPUS, PubMed, and EMBASE were carried out with combined conceptual groups of search terms for 'farming' and 'LBD.' After screening, data were extracted to summarize the study design, sample characteristics, exposure assessment methods, LBD risk factors, demographic information, data collection methods, farm commodities, job context, and sampling strategy. Data were synthesized to determine the weight of evidence for awkward working posture as a risk factor for LBD among farmers.

RESULTS

Nine studies were included in this review. All studies used self-report; there were no field-based studies including direct measurement of awkward posture. There was diversity in exposure definition, exposure assessment, LBD definition, worker characteristics, and analytical approaches. There was evidence to support association between awkward working posture and LBD among farmers.

CONCLUSION

Despite the diversity, the weight of evidence supported a relationship between awkward posture and LBD. Well-designed epidemiological studies with quantitative physical workload assessments, consistent and valid LBD definitions, and longitudinal designs are recommended to clarify the relationship between awkward posture and LBD.

Predicting Forearm Physical Exposures During Computer Work Using Self-Reports, Software-Recorded Computer Usage Patterns, and Anthropometric and Workstation Measurements

Objectives

Alternative techniques to assess physical exposures, such as prediction models, could facilitate more efficient epidemiological assessments in future large cohort studies examining physical exposures in relation to work-related musculoskeletal symptoms. The aim of this study was to evaluate two types of models that predict arm-wrist-hand physical exposures (i.e. muscle activity, wrist postures and kinematics, and keyboard and mouse forces) during computer use, which only differed with respect to the candidate predicting variables; (i) a full set of predicting variables, including self-reported factors, software-recorded computer usage patterns, and worksite measurements of anthropometrics and workstation set-up (full models); and (ii) a practical set of predicting variables, only including the self-reported factors and software-recorded computer usage patterns, that are relatively easy to assess (practical models).

Methods

Prediction models were build using data from a field study among 117 office workers who were symptom-free at the time of measurement. Arm-wrist-hand physical exposures were measured for approximately two hours while workers performed their own computer work. Each worker's anthropometry and workstation set-up were measured by an experimenter, computer usage patterns were recorded using software and self-reported factors (including individual factors, job characteristics, computer work behaviours, psychosocial factors, workstation set-up characteristics, and leisure-time activities) were collected by an online questionnaire. We determined the predictive quality of the models in terms of R2 and root mean squared (RMS) values and exposure classification agreement to low-, medium-, and high-exposure categories (in the practical model only).

Results

The full models had R2 values that ranged from 0.16 to 0.80, whereas for the practical models values ranged from 0.05 to 0.43. Interquartile ranges were not that different for the two models, indicating that only for some physical exposures the full models performed better. Relative RMS errors ranged between 5% and 19% for the full models, and between 10% and 19% for the practical model. When the predicted physical exposures were classified into low, medium, and high, classification agreement ranged from 26% to 71%.

Conclusion

The full prediction models, based on self-reported factors, software-recorded computer usage patterns, and additional measurements of anthropometrics and workstation set-up, show a better predictive quality as compared to the practical models based on self-reported factors and recorded computer usage patterns only. However, predictive quality varied largely across different arm-wrist-hand exposure parameters. Future exploration of the relation between predicted physical exposure and symptoms is therefore only recommended for physical exposures that can be reasonably well predicted.

A Lower Level of Physically Demanding Work Is Associated with Excellent Work Ability in Men and Women with Neck Pain in Different Age Groups

BACKGROUND

The aim of this study was to investigate which physical and psychosocial work demands were associated with excellent work ability in individuals with neck pain, and to investigate age and sex differences in these associations.

METHODS

The study sample was obtained from the Statistics Sweden cross-sectional Work Environment survey and consisted of workers who reported neck pain after work (N = 3,212).

RESULTS

The findings showed an association between excellent work ability and self-reported low exposure to lifting, twisted work posture, working with hands in shoulder level or higher, and leaning forward without support and combination of exposures containing these work demands. Low exposure to seated work and high demands showed a reversed association. The associations were present mainly among older workers and were generally stronger for men than for women.

CONCLUSION

This study indicates that a lower level of physically demanding work is an important element to maintain excellent work ability, especially for the older worker with neck pain.

Real time RULA assessment using Kinect v2 sensor

The evaluation of the exposure to risk factors in workplaces and their subsequent redesign represent one of the practices to lessen the frequency of work-related musculoskeletal disorders. In this paper we present K2RULA, a semi-automatic RULA evaluation software based on the Microsoft Kinect v2 depth camera, aimed at detecting awkward postures in real time, but also in off-line analysis. We validated our tool with two experiments. In the first one, we compared the K2RULA grand-scores with those obtained with a reference optical motion capture system and we found a statistical perfect match according to the Landis and Koch scale (proportion agreement index = 0.97, k = 0.87). In the second experiment, we evaluated the agreement of the grand-scores returned by the proposed application with those obtained by a RULA expert rater, finding again a statistical perfect match (proportion agreement index = 0.96, k = 0.84), whereas a commercial software based on Kinect v1 sensor showed a lower agreement (proportion agreement index = 0.82, k = 0.34).

Ergonomic analysis of construction worker's body postures using wearable mobile sensors

Construction jobs are more labor-intensive compared to other industries. As such, construction workers are often required to exceed their natural physical capability to cope with the increasing complexity and challenges in this industry. Over long periods of time, this sustained physical labor causes bodily injuries to the workers which in turn, conveys huge losses to the industry in terms of money, time, and productivity. Various safety and health organizations have established rules and regulations that limit the amount and intensity of workers' physical movements to mitigate work-related bodily injuries. A precursor to enforcing and implementing such regulations and improving the ergonomics conditions on the jobsite is to identify physical risks associated with a particular task. Manually assessing a field activity to identify the ergonomic risks is not trivial and often requires extra effort which may render it to be challenging if not impossible. In this paper, a low-cost ubiquitous approach is presented and validated which deploys built-in smartphone sensors to unobtrusively monitor workers' bodily postures and autonomously identify potential work-related ergonomic risks. Results indicates that measurements of trunk and shoulder flexions of a worker by smartphone sensory data are very close to corresponding measurements by observation. The proposed method is applicable for workers in various occupations who are exposed to WMSDs due to awkward postures. Examples include, but are not limited to industry laborers, carpenters, welders, farmers, health assistants, teachers, and office workers.

3D peak and cumulative low back and shoulder loads and postures during greenhouse pepper harvesting using a video-based approach

BACKGROUND

In agricultural field work many tasks have been cited as high priority risk factors for the development of work-related musculoskeletal disorders (WRMDs). Although video-based biomechanical approaches have been effective in documenting the physical demands and risks associated with various occupational and non-occupational tasks, to date, this method has yet to be used to document jobs such as crop harvesting in a greenhouse environment.

OBJECTIVE

To document and assess the postural characteristics and 3D peak and cumulative low back and shoulder loads associated with greenhouse pepper harvesting using a video-based posture sampling approach.

METHODS

Nine male (28.2 (4.1) years) pepper harvesters from a greenhouse in Southwestern Ontario, Canada were videotaped during a normal shift. 3DMatch was used to document working trunk and shoulder postures, from which 3D peak and cumulative forces and moments were quantified.

RESULTS

On average, workers spent the majority of their time in neutral trunk postures (lateral bend: 99.1%; axial twist: 59.9%; flexion: 89.8%). Consistent results were found for the left and right shoulder, with the arms held in a neutral flexion posture 50% of the time or more. Four participants experienced peak L4/L5 compression forces (between 4116.3 N and 5937.0 N) which exceeded the NIOSH Action Limit (3400 N) during the cart pushing/pulling task, but remained below the threshold during picking. Mean cumulative L4/L5 extension and shoulder flexion moments ranged in magnitude from 18.5 Nm to 28.2 Nm, and between 19.4 Nm and 23.2 Nm, respectively, across all tasks.

CONCLUSIONS

The postural characteristics and biomechanical loads associated with greenhouse pepper harvesting were quantified with a video-based biomechanical approach. Further investigations of the physical risk factors for low back and shoulder musculoskeletal disorders is warranted in pepper harvesting, given the postures and loads documented in this study.

The variability of the trunk forward bending in standing activities during work vs. leisure time

High level of occupational physical activity (PA), contrary to leisure time activities, is generally associated with detrimental health outcomes. We hypothesized that this contrast may be associated with a different pattern of exposure variability in PA, e.g., forward bending of the trunk. The study was conducted on 657 blue-collar workers. Two accelerometers were used to identify the body posture and forward bending of the trunk during work and leisure time. The pattern of forward bending was analyzed using exposure variation analysis (EVA). The recordings comprised of 2.6 ± 0.97 working days in average, with 19.9 ± 8.1 h work and 22.9 ± 8.9 h leisure. The standard deviation and entropy of the EVA profile indicated 11% and 6% (for about 80% of subjects) less variable pattern during work compared with the leisure time, respectively. These new findings contribute to the understanding the paradoxical outcomes of PA during work and leisure.

Exposure-response relationships for work-related neck and shoulder musculoskeletal disorders--Analyses of pooled uniform data sets

There is a lack of quantitative data regarding exposure-response relationships between occupational risk factors and musculoskeletal disorders in the neck and shoulders. We explored such relationships in pooled data from a series of our cross-sectional studies. We recorded the prevalence of complaints/discomfort (Nordic Questionnaire) and diagnoses (physical examination) in 33 groups (24 female and 9 male) within which the workers had similar work tasks (3141 workers, of which 817 were males). In representative sub-groups, we recorded postures and velocities of the head (N = 299) and right upper arm (inclinometry; N = 306), right wrist postures and velocities (electrogoniometry; N = 499), and muscular activity (electromyography) in the right trapezius muscle (N = 431) and forearm extensors (N = 206). We also assessed the psychosocial work environment (Job Content Questionnaire). Uni- and multivariate linear meta-regression analysis revealed several statistically significant group-wise associations. Neck disorders were associated with head inclination, upper arm elevation, muscle activity of the trapezius and forearm extensors and wrist posture and angular velocity. Right-side shoulder disorders were associated with head and upper arm velocity, activity in the trapezius and forearm extensor muscles and wrist posture and angular velocity. The psychosocial work environment (low job control, job strain and isostrain) was also associated with disorders. Women exhibited a higher prevalence of neck and shoulder complaints and tension neck syndrome than men, when adjusting for postures, velocities, muscular activity or psychosocial exposure. In conclusion, the analyses established quantitative exposure-response relationships between neck and shoulder disorders and objective measures of the physical workload on the arm. Such information can be used for risk assessment in different occupations/work tasks, to establish quantitative exposure limits, and for the evaluation of preventive measures.

The impact of work related physical activity and leisure physical activity on the risk and prognosis of neck pain - a population based cohort study on workers

BACKGROUND

The effect of physical activity on risk and prognosis for neck pain has been studied earlier with inconclusive results. There is a need for large prospective studies on the subject. The aim of this study was to investigate if work related physical activity and physical activity during leisure time are of importance for the risk and prognosis of neck pain in men and women.

METHODS

We used the Stockholm Public Health Cohort and formed two sub-cohorts of the working population based on data from 2002. Cohort I (risk cohort) included persons without neck pain (n = 4681), and cohort II (prognostic cohort) included persons with occasional neck pain (n = 6820) during the previous six months. Both cohorts were assessed for the outcome long duration troublesome neck pain (LDNP) in 2007. The exposures and potential confounders were assessed through a questionnaire in 2002. The question regarding work related physical activity over the past 12 months had five answering categories ranging from "sedentary" to"heavy". The question regarding leisure physical activity for the past 12 months had five answering categories ranging from "sedentary" to "regular physical activity". LDNP in 2007 was defined as having had troublesome neck pain lasting ≥ 3 consecutive months during the previous five years. Associations between work related physical activity and LDNP, as well as leisure physical activity and LDNP, were investigated by multivariable logistic regression, considering potential confounding factors.

RESULTS

In cohort I (risk cohort) we found an association between leisure physical activity and LDNP. In cohort II (prognostic cohort) we found no association between the exposures and the outcome.

CONCLUSION

The results suggest that leisure physical activity has a protective effect on the risk of developing LDNP in a population free from neck pain. It did not, however, affect the prognosis of occasional neck pain. Neither the risk nor the prognosis of neck pain was affected by work related physical activity in this study.

Exposure-response relationships between movements and postures of the wrist and carpal tunnel syndrome among male and female house painters: a retrospective cohort study

OBJECTIVES

To investigate exposure-response relationships between measured movements and postures of the wrist and the incidence of carpal tunnel syndrome (CTS), and any modifications by sex.

METHODS

In 2011, we established a historical cohort of 9364 members of the Painters' Union in Denmark. Self-reported task distributions were obtained by questionnaire (53% responded) and combined with sex-specific task exposure matrices to get individual estimates of exposure intensity, that is, velocity of wrist flexion/extension, mean power frequency (MPF) and non-neutral wrist postures. Exposure duration was assessed from yearly working proportions. Registered first-time hospital discharge CTS diagnoses and CTS surgery were collected as outcomes. The cohort was followed from 1994 to 2010. Log-linear Poisson regression was used.

RESULTS

For CTS diagnoses, the adjusted incidence rate ratios (IRRs) increased with increasing wrist velocity (IRR=1.37 (95% CI 1.10 to 1.71) per °/s) and MPF (IRR=1.53 (95% CI 1.21 to 1.91) per 0.01 Hz). For CTS surgery, the results were similar. The outcomes were not related to non-neutral postures or exposure duration. The adjusted IRRs for women were higher than those for men. There were no multiplicative interaction effects between exposure intensity, exposure duration and sex. However, the absolute incidence rates (IRs) increased at a steeper rate for women than for men, indicating an additive interaction.

CONCLUSIONS

The incidence of CTS increased with increasing velocity of wrist flexion/extension and MPF of wrist movements. The relative increase in incidence rates was the same for women and men, but the absolute incidence rates increased at a steeper rate for women than for men.

Detailed assessment of low-back loads may not be worth the effort: A comparison of two methods for exposure-outcome assessment of low-back pain

The trade-off between feasibility and accuracy of measurements of physical exposure at the workplace has often been discussed, but is unsufficiently understood. We therefore explored the effect of two low-back loading measurement tools with different accuracies on exposure estimates and their associations with low-back pain (LBP). Low-back moments of 93 workers were obtained using two methods: a moderately accurate observation-based method and a relatively more accurate video-analysis method. Group-based exposure metrics were assigned to a total of 1131 workers who reported on their LBP status during three follow-up years. The two methods were compared regarding individual and group-based moments and their predictive value for LBP. Differences between the two methods for peak moments were high at the individual level and remained substantial at group level. For cumulative moments, differences between the two methods were attenuated as random inaccuracies cancelled out. Peak moments were not predictive for LBP in any method while cumulative moments were, suggesting comparable predictive values of the two methods. While assessment of low-back load improves from investing in collecting relatively more accurate individual-based data, this does not necessarily lead to better predictive values on a group level, especially not for cumulative loads.

Influence of musculoskeletal pain on workers' ergonomic risk-factor assessments

This study compares the ergonomic risk-factor assessments of workers with and without musculoskeletal pain. A questionnaire on the musculoskeletal pain experienced in various body regions during the 12 months and seven days preceding the data collection was administered to 473 workers from three industrial sectors. The Ergonomic Workplace Analysis method, developed by the Finnish Institute of Occupational Health (FIOH), was then used by the workers and an ergonomics expert to assess the workstations. The ergonomic quality of the workstations and the need for change were also assessed by the expert and the workers at the workstation, using visual analog scales (VAS). Results show that the workers in this study were exposed to significant musculoskeletal disorder (MSD) risk factors, according to the FIOH assessment and the high percentages of reported pain. The results also show that those who reported pain in the seven days prior to the assessment evaluated their workstations more negatively than subjects who reported no pain, while the expert found no difference between the two groups' exposure to MSD risk factors.

Factors affecting the perception of whole-body vibration of occupational drivers: an analysis of posture and manual materials handling and musculoskeletal disorders

Due to the high cost of conducting field measurements, questionnaires are usually preferred for the assessment of physical workloads and musculoskeletal disorders (MSDs). This study compares the physical workloads of whole-body vibration (WBV) and awkward postures by direct field measurements and self-reported data of 45 occupational drivers. Manual materials handling (MMH) and MSDs were also investigated to analyse their effect on drivers' perception. Although the measured values for WBV exposure were very similarly distributed among the drivers, the subjects' perception differed significantly. Concerning posture, subjects seemed to estimate much better when the difference in exposure was significantly large. The percentage of measured awkward trunk and head inclination were significantly higher for WBV-overestimating subjects than non-overestimators; 77 and 80% vs. 36 and 33%. Health complaints in terms of thoracic spine, cervical spine and shoulder-arm were also significantly more reported by WBV-overestimating subjects (42, 67, 50% vs. 0, 25, 13%, respectively). Although more MMH was reported by WBV-overestimating subjects, there was no statistical significance in this study.

PRACTITIONER SUMMARY

Self-reported exposures of occupational drivers are affected by many other cofactors, and this can result in misinterpretations. A comparison between field measurement and questionnaire was used to highlight the factors affecting the perception of drivers for whole-body vibration (WBV) exposure. Posture and musculoskeletal disorders influenced the perception of the similarly WBV-exposed drivers significantly.

Is objectively measured sitting time associated with low back pain? A cross-sectional investigation in the NOMAD study

Background

Studies on the association between sitting time and low back pain (LBP) have found contrasting results. This may be due to the lack of objectively measured sitting time or because socioeconomic confounders were not considered in the analysis.

Objectives

To investigate the association between objectively measured sitting time (daily total, and occupational and leisure-time periods) and LBP among blue-collar workers.

Methods

Two-hundred-and-one blue-collar workers wore two accelerometers (GT3X+ Actigraph) for up to four consecutive working days to obtain objective measures of sitting time, estimated via Acti4 software. Workers reported their LBP intensity the past month on a scale from 0 (no pain) to 9 (worst imaginable pain) and were categorized into either low (≤5) or high (>5) LBP intensity groups. In the multivariate-adjusted binary logistic regression analysis, total sitting time, and occupational and leisure-time sitting were both modeled as continuous (hours/day) and categorical variables (i.e. low, moderate and high sitting time).

Results

The multivariate logistic regression analysis showed a significant positive association between total sitting time (per hour) and high LBP intensity (odds ratio; OR=1.43, 95%CI=1.15-1.77, P=0.01). Similar results were obtained for leisure-time sitting (OR=1.45, 95%CI=1.10-1.91, P=0.01), and a similar but non-significant trend was obtained for occupational sitting time (OR=1.34, 95%CI 0.99-1.82, P=0.06). In the analysis on categorized sitting time, high sitting time was positively associated with high LBP for total (OR=3.31, 95%CI=1.18-9.28, P=0.03), leisure (OR=5.31, 95%CI=1.57-17.90, P=0.01), and occupational (OR=3.26, 95%CI=0.89-11.98, P=0.08) periods, referencing those with low sitting time.

Conclusion

Sitting time is positively associated with LBP intensity among blue-collar workers. Future studies using a prospective design with objective measures of sitting time are recommended.

Mechanical stress

This chapter discusses mechanical stressors that are believed to be associated with work-related musculoskeletal disorders. It starts with an introduction to work-related musculoskeletal disorders (particularly those with high incidences in workplaces, such as disorders of low back, neck/shoulder, hand/wrist, elbow, and knee) in high-risk industries, and those mechanical stressors (such as high forces, awkward postures, high repetitions, excessive contact stress, and harmful human vibrations) in workplaces that are responsible for these disorders. Quantification methods of these mechanical stressors are then discussed. Although various quantification methods such as self-report, observational technique, and direct measurement are discussed, details are focused on many of those well-published observational techniques used by practitioners to assess risk levels of these mechanical stressors in jobs. These methods can quantify job mechanical stressors and provide risk level indications that can be used by practitioners to facilitate their decision making. These methods can also be used to evaluate the improvements of ergonomics interventions by comparing the risk levels quantitatively before and after the interventions.

Self-reported physical work exposures and incident carpal tunnel syndrome

BACKGROUND

To prospectively evaluate associations between self-reported physical work exposures and incident carpal tunnel syndrome (CTS).

METHODS

Newly employed workers (n = 1,107) underwent repeated nerve conduction studies (NCS), and periodic surveys on hand symptoms and physical work exposures including average daily duration of wrist bending, forearm rotation, finger pinching, using vibrating tools, finger/thumb pressing, forceful gripping, and lifting >2 pounds. Multiple logistic regression models examined relationships between peak, most recent, and time-weighted average exposures and incident CTS, adjusting for age, gender, and body mass index.

RESULTS

710 subjects (64.1%) completed follow-up NCS; 31 incident cases of CTS occurred over 3-year follow-up. All models describing lifting or forceful gripping exposures predicted future CTS. Vibrating tool use was predictive in some models.

CONCLUSIONS

Self-reported exposures showed consistent risks across different exposure models in this prospective study. Workers' self-reported job demands can provide useful information for targeting work interventions.

The combined effect of physical, psychosocial/organisational and/or environmental risk factors on the presence of work-related musculoskeletal symptoms and its consequences

This study assessed the combined effect of physical and psychosocial/organisational and/or environmental factors on the presence of musculoskeletal symptoms (MSS) and its consequences (reduced activities and absenteeism due to MSS) in a random sample of 3003 workers in New Zealand. By telephone interview, participants reported their current workplace exposures and MSS (neck/shoulder, arm/elbow, wrist and low back) and its consequences. Data were analysed using multivariable logistic regression. Combined exposure to physical and psychosocial/organisational and/or environmental factors increased the odds of MSS in the neck/shoulder (OR 3.14, 95% CI 1.79-5.52), arms/elbow regions (OR 4.14, 95% CI 2.21-7.76) and low back (OR 1.74, 95% CI 1.28-2.37) and its consequences, i.e. reduced activities due to neck/shoulder symptoms (OR 5.45, 95% CI 2.28-13.00), absenteeism due to neck/shoulder symptoms (OR 5.19, 95% CI 2.24-12.01) and absenteeism due to low back symptoms (OR 4.37, 95% CI 2.92-6.53). In contrast, favourable psychosocial/organisational work conditions reduced the odds of wrist symptoms due to poor physical work conditions (OR 2.19, 95% CI 1.44-3.34). We conclude that to reduce MSS and its consequences, employers need to adopt a multifaceted approach: concentrate on improving physical conditions as well as the psychosocial/organisational and environmental aspects of the working environment.

The effect of lifting during work on low back pain: a health impact assessment based on a meta-analysis

Lifting at work is considered an important risk factor for low back pain (LBP). However, contradictory findings have been reported, partly because frequency, duration and intensity (ie, the weight of the load) of lifting have not been systematically considered. This has hampered developments of threshold values for lifting. The aims of this study were: to assess the effect of lifting during work (quantified in duration, frequency or intensity) on the incidence of LBP and to quantify the impact of these relationships on the occurrence of LBP in occupational populations exposed to lifting. We searched in PubMed and EMBASE.com for longitudinal studies assessing the effect of occupational lifting on LBP incidence. For each study, the exposure-response slope of the association was estimated by loglinear regression analysis. When possible, a meta-analysis on these slopes was conducted. In a health impact assessment, the effects of the pooled exposure-response relationships on LBP incidence was assessed. Eight longitudinal studies were included. Pooled estimates resulted in ORs of 1.11 (1.05 to 1.18) per 10 kg lifted and 1.09 (1.03 to 1.15) per 10 lifts/day. Duration of lifting could not be pooled. Using these ORs, we estimated that lifting loads over 25 kg and lifting at a frequency of over 25 lifts/day will increase the annual incidence of LBP by 4.32% and 3.50%, respectively, compared to the incidence of not being exposed to lifting. Intensity and frequency of lifting significantly predict the occurrence of LBP. Exposure-response relationships show that lifting heavy loads may have a substantial impact on musculoskeletal health of the working population. This information may direct the development of occupational lifting guidelines and workplace design for LBP prevention.

The NIOSH lifting equation and low-back pain, Part 1: Association with low-back pain in the backworks prospective cohort study

OBJECTIVE

The aim of this study was to evaluate relationships between the revised NIOSH lifting equation (RNLE) and risk of low-back pain (LBP).

BACKGROUND

The RNLE is commonly used to quantify job physical stressors to the low back from lifting and/or lowering of loads. There is no prospective study on the relationship between RNLE and LBP that includes accounting for relevant covariates.

METHOD

A cohort of 258 incident-eligible workers from 30 diverse facilities was followed for up to 4.5 years. Job physical exposures were individually measured. Worker demographics, medical history, psychosocial factors, hobbies, and current LBP were obtained at baseline. The cohort was followed monthly to ascertain development of LBP and quarterly to determine changes in job physical exposure. The relationship between LBP and peak lifting index (PLI) and peak composite lifting index (PCLI) were tested in multivariate models using proportional hazards regression.

RESULTS

Point and lifetime prevalences of LBP at baseline were 7.1% and 75.1%, respectively. During follow-up, there were 123 incident LBP cases. Factors predicting development of LBP included job physical exposure (PLI and PCLI), history of LBP, psychosocial factors, and housework. In adjusted models, risk (hazard ratio [HR]) increased per-unit increase in PLI and PCLI (p = .05 and .02; maximum HR = 4.3 and 4.2, respectively). PLI suggested a continuous increase in risk with an increase in PLI, whereas the PCLI showed elevated, but somewhat reduced, risk at higher exposures.

CONCLUSION

Job physical stressors are associated with increased risk of LBP. Data suggest that the PLI and PCLI are useful metrics for estimating exposure to job physical stressors.

Is Borg's perceived exertion scale a useful indicator of muscular and cardiovascular load in blue-collar workers with lifting tasks? A cross-sectional workplace study

Purpose

To investigate associations between perceived exertion and objectively assessed muscular and cardiovascular load during a full working day among workers with manual lifting tasks.

Methods

A total of 159 men and 41 women from 14 workplaces with manual lifting tasks participated. Participants reported perceived exertion (BORG-CR10) at midday and after work. Surface electromyography of the thigh, lower back and neck muscles were normalized to isometric voluntary contractions (MVC) to express relative muscle load during the day. Cardiovascular load was measured with electrocardiography and calculated as the average percentage of the heart rate reserve capacity (((heart rate during work – resting heart rate) / (maximum heart rate − resting heart rate)) * 100) during the day.

Results

Using linear regression, significant but weak associations (β < 0.23) were observed between perceived exertion and (1) high muscle activity (>60 % of MVC) of the neck muscles and (2) inactivity (<1 % of MVC) of the thigh muscles and (3) cardiovascular load, respectively. Using logistic regression, perceived exertion ≥4 (high exertion), referencing <4 (low-to-moderate exertion), was related to high activity of the trapezius muscle [OR 18 (95 % CI 2–143)], i.e., the odds for experiencing high exertion during work increased 18-fold for each percentage increase in time above 60 % MVC.

Conclusions

During a full working day among blue-collar workers with lifting tasks, high neck muscle activity increases the odds for experiencing high perceived physical exertion. Perceived exertion of at least 4 on the BORG CR10 scale appears to be a good indicator that high muscular loading occurs.

Electronic supplementary material

The online version of this article (doi:10.1007/s00421-013-2782-9) contains supplementary material, which is available to authorized users.

Inter-rater reliability of a video-analysis method measuring low-back load in a field situation

Valid and reliable low-back load assessment tools that can be used in field situations are needed for epidemiologic studies and for ergonomic practice. The aim of this study was to assess the inter-rater reliability of a low-back load video-analysis method in a field setting. Five raters analyzed 50 work site manual material handling tasks of 14 workers. Peak and mean moments at the level of L5S1, and segment angles were obtained using the video-analysis method. Intra-class correlation coefficients (ICCs) and median standard deviations across raters were calculated. ICCs revealed excellent inter-rater reliability (>0.9) for peak and mean moments, ICCs of segment angles were variable. Median standard deviations showed relatively small inter-rater variance for moments (standard deviation <10 Nm) and segment angle variation ranging from 0° to 20°. The proposed video-analysis method, provides a reliable tool for obtaining low-back loads from occupational field tasks.

Physical activities at work and risk of musculoskeletal pain and its consequences: protocol for a study with objective field measures among blue-collar workers

Background

Among blue-collar workers, high physical work demands are generally considered to be the main cause of musculoskeletal pain and work disability. However, current available research on this topic has been criticised for using self-reported data, cross-sectional design, insufficient adjustment for potential confounders, and inadequate follow-up on the recurrent and fluctuating pattern of musculoskeletal pain. Recent technological advances have provided possibilities for objective diurnal field measurements of physical activities and frequent follow-up on musculoskeletal pain.

The main aim of this paper is to describe the background, design, methods, limitations and perspectives of the Danish Physical Activity cohort with Objective measurements (DPhacto) investigating the association between objectively measured physical activities capturing work and leisure time and frequent measurements of musculoskeletal pain among blue-collar workers.

Methods/design

Approximately 2000 blue-collar workers are invited for the study and asked to respond to a baseline questionnaire, participate in physical tests (i.e. muscle strength, aerobic fitness, back muscle endurance and flexibility), to wear accelerometers and a heart rate monitor for four consecutive days, and finally respond to monthly text messages regarding musculoskeletal pain and quarterly questionnaires regarding the consequences of musculoskeletal pain on work activities, social activities and work ability for a one-year follow-up period.

Discussion

This study will provide novel information on the association between physical activities at work and musculoskeletal pain. The study will provide valid and precise documentation about the relation between physical work activities and musculoskeletal pain and its consequences among blue-collar workers.

Prevalence of low back symptoms and its consequences in relation to occupational group

BACKGROUND

The purpose of this study was to examine: (1) the prevalence of low back symptoms (LBS) and its consequences (reduced activities and absenteeism); (2) the association between occupational group and LBS; and (3) the association between LBS and its consequences.

METHODS

A self-administered questionnaire was used to determine the prevalence of LBS in 1,294 Indonesian coal mining workers. A Cox proportional hazards model was developed to quantify the 12-monthly hazard of LBS. Logistic regression models were developed to identify risk factors for reduced activity and absenteeism from the workplace.

RESULTS

The 12-month period prevalence for LBS, reduced activities, and absenteeism were 75%, 16%, and 13%, respectively. The 12-monthly hazard of LBS for blue-collar workers was 1.85 (95% CI: 1.06-3.25) times that of white-collar workers. LBS and smoking increased the risk of reduced activity and absenteeism.

CONCLUSIONS

Indonesian coal mining workers have a high prevalence of LBS. The findings imply that efforts to reduce LBS and in the workplace should focus on blue-collar workers. For smokers who report reduced activities and/or absenteeism, there should be a focus on rehabilitation and/or return-to-work programs.

Exposure-response relationships in work-related musculoskeletal disorders in elbows and hands - A synthesis of group-level data on exposure and response obtained using uniform methods of data collection

There is a serious lack of quantitative data regarding exposure-response relationships between occupational risk factors and musculoskeletal elbow and hand disorders. This paper explores such relationships in group-level data from our earlier cross-sectional studies. Prevalence of complaints (Nordic Questionnaire) and diagnoses (physical examination) were recorded in 19 groups of female workers (1891 individuals), and 8 groups of male workers (761 individuals), with highly similar work tasks within each group. Linear regression was performed on the group means of wrist postures and angular velocity (obtained by electrogoniometers), as well as muscular load (obtained using electromyography), recorded in representative sub-samples, and psychosocial exposure (Job Content Questionnaire). To tackle within-group variations in physical exposure, sensitivity analyses were performed by bootstrapping simulations, rendering confidence intervals. The sex-adjusted slope of the regression line (β) for wrist angular velocity vs. complaints during the past 7 days was 0.6%/(°/s), (95% CI 0.3-0.9), and for carpal tunnel syndrome (CTS) 0.2%/(°/s), (0.1-0.3). For palmar flexion, p50, β over the past 7 days was 0.8%/° (0.4-1.2); for CTS 0.3%/° (0.1-0.5); β for muscular activity p90: 0.9%/%MVE (0.3-1.6), and 0.3%/%MVE (-0.03-0.6) respectively and finally β for muscular rest: -1.2%/%time (-2.4-0.03) and -0.5%/%time (-0.9 to -0.01). Relationships were also demonstrated for low job control, job strain and isostrain. Women exhibited a higher prevalence of complaints than men. In conclusion, we have established quantitative exposure-response relationships between physical work load and elbow/hand disorders. Wrist angular velocity was the most consistent risk factor.

Work-site musculoskeletal pain risk estimates by trained observers--a prospective cohort study

Work-related musculoskeletal pain (MSP) risk assessments by trained observers are often used in ergonomic practice; however, the validity may be questionable. We investigated the predictive value of work-site MSP risk estimates in a prospective cohort study of 1745 workers. Trained observers estimated the risk of MSP (neck, shoulder or low-back pain) using a three-point scale (high, moderate and low risk) after observing a video of randomly selected workers representing a task group. Associations of the estimated risk of pain and reported pain during a three-year follow-up were assessed using logistic regression. Estimated risk of neck and shoulder pain did (odds ratio, OR: 1.45 (95% confidence interval, CI: 1.01-2.08); 1.64 (95% CI: 1.05-2.55)), however, estimated risk of low-back pain did not significantly predict pain (OR: 1.27 (95% CI: 0.91-1.79)). The results show that observers were able to estimate the risk of shoulder and neck pain, whereas they found it difficult to estimate the risk of low-back pain. Practitioner Summary: Work-related musculoskeletal pain risk assessments by observers are often used in ergonomic practice. We showed that observers were able to estimate shoulder and neck pain risk, but had difficulties to estimate the risk of low-back pain. Therefore, observers' risk estimates might provide a useful method for musculoskeletal pain risk assessments.

Data collection costs in industrial environments for three occupational posture exposure assessment methods

Background

Documentation of posture measurement costs is rare and cost models that do exist are generally naïve. This paper provides a comprehensive cost model for biomechanical exposure assessment in occupational studies, documents the monetary costs of three exposure assessment methods for different stakeholders in data collection, and uses simulations to evaluate the relative importance of cost components.

Methods

Trunk and shoulder posture variables were assessed for 27 aircraft baggage handlers for 3 full shifts each using three methods typical to ergonomic studies: self-report via questionnaire, observation via video film, and full-shift inclinometer registration. The cost model accounted for expenses related to meetings to plan the study, administration, recruitment, equipment, training of data collectors, travel, and onsite data collection. Sensitivity analyses were conducted using simulated study parameters and cost components to investigate the impact on total study cost.

Results

Inclinometry was the most expensive method (with a total study cost of € 66,657), followed by observation (€ 55,369) and then self report (€ 36,865). The majority of costs (90%) were borne by researchers. Study design parameters such as sample size, measurement scheduling and spacing, concurrent measurements, location and travel, and equipment acquisition were shown to have wide-ranging impacts on costs.

Conclusions

This study provided a general cost modeling approach that can facilitate decision making and planning of data collection in future studies, as well as investigation into cost efficiency and cost efficient study design. Empirical cost data from a large field study demonstrated the usefulness of the proposed models.