Work with prolonged arm elevation as a risk factor for shoulder pain: a longitudinal study among young adults

Reliability and Accuracy of Standard Reference Procedures for Measurements of Trunk and Arm Postures in Ergonomics

Adequate reference procedures for obtaining the reference zero-angle position are important for precise and accurate posture measurements, but few studies have systematically investigated these. A limited number of previous studies suggest differences in accuracy between procedures, with some causing an underestimation of the true arm elevation angle when sensors are taped to the skin. The reliability of commonly used reference procedures for the measurement of the trunk posture is also not well explored, and alternative procedures may improve precision. Based on this identified gap, this study evaluated the test-retest reliability of the N-position (I-pose), i.e., the standard procedure for recording trunk postures, and compared it with two new alternative procedures. Additionally, the accuracy of the N-position for measuring arm elevation angles was compared with one alternative procedure. A total of 40 participants (22 women and 18 men) aged 26-70 years performed the reference procedures in a laboratory setting. Postures were recorded using a smart workwear system equipped with two inertial measurement units (IMUs) embedded in pockets within the workwear. For the trunk posture, the N-position showed a slight lack of test-retest reliability, while one of the alternative procedures demonstrated better test-retest reliability. For the arm posture, the N-position, which does not include lateral trunk inclination, resulted in a substantial underestimation of the arm elevation angle of approximately 15°, which is a novel finding. In contrast, the posture involving trunk inclination closely matched the targeted reference, with a difference of less than 2°. This study underscores the importance of selecting appropriate reference procedures to ensure precise and accurate posture measurements.

Wearable Motion Capture Devices for the Prevention of Work-Related Musculoskeletal Disorders in Ergonomics-An Overview of Current Applications, Challenges, and Future Opportunities

Work-related musculoskeletal disorders (WMSDs) are a major contributor to disability worldwide and substantial societal costs. The use of wearable motion capture instruments has a role in preventing WMSDs by contributing to improvements in exposure and risk assessment and potentially improved effectiveness in work technique training. Given the versatile potential for wearables, this article aims to provide an overview of their application related to the prevention of WMSDs of the trunk and upper limbs and discusses challenges for the technology to support prevention measures and future opportunities, including future research needs. The relevant literature was identified from a screening of recent systematic literature reviews and overviews, and more recent studies were identified by a literature search using the Web of Science platform. Wearable technology enables continuous measurements of multiple body segments of superior accuracy and precision compared to observational tools. The technology also enables real-time visualization of exposures, automatic analyses, and real-time feedback to the user. While miniaturization and improved usability and wearability can expand the use also to more occupational settings and increase use among occupational safety and health practitioners, several fundamental challenges remain to be resolved. The future opportunities of increased usage of wearable motion capture devices for the prevention of work-related musculoskeletal disorders may require more international collaborations for creating common standards for measurements, analyses, and exposure metrics, which can be related to epidemiologically based risk categories for work-related musculoskeletal disorders.

Effect of Expertise on Shoulder and Upper Limb Kinematics, Electromyography, and Estimated Muscle Forces During a Lifting Task

OBJECTIVE

To highlight the working strategies used by expert manual handlers compared with novice manual handlers, based on recordings of shoulder and upper limb kinematics, electromyography (EMG), and estimated muscle forces during a lifting task.

BACKGROUND

Novice workers involved in assembly, manual handling, and personal assistance tasks are at a higher risk of upper limb musculoskeletal disorders (MSDs). However, few studies have investigated the effect of expertise on upper limb exposure during workplace tasks.

METHOD

Sixteen experts in manual handling and sixteen novices were equipped with 10 electromyographic electrodes to record shoulder muscle activity during a manual handling task consisting of lifting a box (8 or 12 kg), instrumented with three six-axis force sensors, from hip to eye level. Three-dimensional trunk and upper limb kinematics, hand-to-box contact forces, and EMG were recorded. Then, joint contributions, activation levels, and muscle forces were calculated and compared between groups.

RESULTS

Sternoclavicular-acromioclavicular joint contributions were higher in experts at the beginning of the movement, and in novices at the end, whereas the opposite was observed for the glenohumeral joint. EMG activation levels were 37% higher for novices but predicted muscle forces were higher in experts.

CONCLUSION

This study highlights significant differences between experts and novices in shoulder kinematics, EMG, and muscle forces; hence, providing effective work guidelines to ensure the development of a safe handling strategy is important.

APPLICATION

Shoulder kinematics, EMG, and muscle forces could be used as ergonomic tools to identify inappropriate techniques that could increase the prevalence of shoulder injuries.

Differences between men and women in their risk of work injury and disability: A systematic review

Background

Health responses associated with occupational exposures can vary between men and women.

Aims

This study reviewed the work injury and disability risks associated with similar types of occupational exposures for men and women within and across occupations.

Materials & Methods

A systematic review was undertaken of observational studies published between 2009 and 2019. Studies were required to empirically compare men and women for associations between occupational exposures and work injury or disability outcomes. Included studies were appraised for methodological quality and medium to high rated studies were compared for risk differences between men and women.

Results

Of 14,006 records identified, 440 articles were assessed for methodological quality, and 33 medium to high rated studies were included and reviewed. Among all occupations, the association between physical exposures, job demands, noise, and repetitive tasks, and injury risk were stronger among men. The relationship between repetitive tasks and sickness absence was stronger among women. Most studies examining psychological exposures found no risk differences for men and women across occupations. Men were at higher injury risk in certain occupations in primary and secondary industry sectors involving physical exposures and some chemical/biological exposures. Women were at higher injury risk for the physical demands and repetitive tasks of health care and aluminum production occupations.

Conclusion

This review found that men and women can have different work injury and disability risks, both across and within the same occupations, for some physical exposures and to a lesser extent for some chemical and biological exposures. These differences might be a result of occupation‐specific task differences.

A Cross-Sectional Descriptive Study of Musculoskeletal Disorders (MSDs) of Male Shipbuilding Workers and Factors Associated the Neck, Shoulder, Elbow, Low Back, or Knee MSDs

This study investigates the cross-sectional descriptive characteristics of male shipbuilding workers’ musculoskeletal disorders (MSDs) and factors associated with MSDs in the neck, shoulders, elbows, low back, or knees. From the national compensation data confirmed as MSDs during three years between 2015 and 2017, 985 male workers were analyzed in terms of age, work experience, occupations, company size, and MSD type according to each body region. In the analysis of frequency and severity according to ‘occupation–body region–MSD type’, ‘Electrician/plumber–low back–herniated disc’ (6.9%) was the form of MSDs with the highest frequency among total MSDs, and ‘Crane–neck–herniated disc’ (500.5 days) was the highest mean of sick leave days. The low back MSDs (28.9%) were the highest frequency, followed by shoulders (27.7%) and knees (16.2%). The herniated disc was frequent in the neck and lumbar region, and the mean of sick leave days of the neck herniated disc (402.2 days) was greater than that of the low back herniated disc (321.1 days). While a rupture was frequent in the shoulder or knee region, the mean of sick leave days for shoulder rupture (335.1 days) was greater than that of the knee rupture (318.8 days). In the binary logistic regression analysis, age was positively associated with MSDs in the neck, shoulder, or elbow regions, while the low back MSDs category was not positively associated with age. Large companies with >1000 employees were highly associated with neck MSDs, while small companies with <30 employees were related to the low back MSDs. This study derives the characteristics for frequency and sick leave days of MSDs in the neck, shoulders, elbows, low back, or knees to prioritize MSD prevention information. The results of this study can be used as primary data for establishing MSD prevention policy.

Shoulder electromyography-based indicators to assess manifestation of muscle fatigue during laboratory-simulated manual handling task

Muscle fatigue is a risk factor for developing shoulder musculoskeletal disorders. The aim of this study was to identify shoulder electromyographic indicators that are most indicative of muscle fatigue during a laboratory simulated manual handling task. Thirty-two participants were equipped with electromyographic electrodes on 10 shoulder muscles and moved boxes for 45-minutes. The modified rate of perceived exertion (mRPE) was assessed every 5-minutes and multivariate linear regressions were performed between myoelectric manifestation of fatigue (MMF) and the mRPE scores. During a manual handling task representative of industry working conditions, spectral entropy, median frequency, and mobility were the electromyographic indicators that explained the largest percentage of the mRPE. Overall, the deltoids, biceps and upper trapezius were the muscles that most often showed significant changes over time in their electromyographic indicators. The combination of these three indicators may improve the accuracy for the assessment of MMF during manual handling. Practitioner Summary: To date, muscle fatigue has primarily been assessed during tasks done to exhaustion, which are not representative of typical working conditions. During a manual handling task representative of industry working conditions, EMG-derived spectral entropy, and median frequency, both extracted from time-frequency analysis, and mobility extracted from time domain, were the best indicators of the manifestation of muscle fatigue.

Sex and Gender Differences in Occupational Hazard Exposures: a Scoping Review of the Recent Literature

PURPOSE OF REVIEW

Comparative research on sex and/or gender differences in occupational hazard exposures is necessary for effective work injury and illness prevention strategies. This scoping review summarizes the peer-reviewed literature from 2009 to 2019 on exposure differences to occupational hazards between men and women, across occupations, and within the same occupation.

RECENT FINDINGS

Fifty-eight studies retrieved from eight databases met our inclusion criteria. Of these, 30 studies were found on physical hazards, 38 studies on psychological/psychosocial hazards, 5 studies on biological hazards, and 17 studies on chemical hazards. The majority of studies reported that men were exposed to noise, vibration, medical radiation, physically demanding work, solar radiation, falls, biomechanical risks, chemical hazards, and blood contamination; while women were exposed to wet work, bullying and discrimination, work stress, and biological agents. Within the same occupations, men were more likely to be exposed to physical hazards, with the exception of women in health care occupations and exposure to prolonged standing. Women compared to men in the same occupations were more likely to experience harassment, while men compared to women in the same occupations reported higher work stress. Men reported more exposure to hazardous chemicals in the same occupations as women. The review suggests that men and women have different exposures to occupational hazards and that these differences are not solely due to a gendered distribution of the labor force by occupation. Findings may inform prevention efforts seeking to reduce gender inequalities in occupational health. Future research is needed to explain the reasons for sex/gender inequality differences in exposures within the same occupation.

The effect of task rotation on activation and fatigue response of rotator cuff muscles during overhead work

Overhead work is known as one of the ergonomic risk factors that can lead to shoulder overload and injury. Anatomical alignment of rotator cuff muscles makes them the most vulnerable to injuries during overhead work. In this study, the effect of task rotation, as one of the administrative controls to reduce the risk of injury during overhead work, on the fatigue response of rotator cuff muscles was investigated. Twelve participants performed three submaximal exertions (5, 20, and 35% of maximum voluntary contraction (MVC)) using four task rotation sequences (increasing, decreasing, upward parabolic, and downward parabolic). Median frequency of surface electromyography (EMG), shoulder strength, and ratings of perceived exertion (RPE) were used to study the fatigue response of rotator cuff muscles. Although the average normalized muscle activity was similar in all sequences, the task rotation sequence had a significant effect on the median frequency. The effect of task rotation sequence on the strength and RPE was similar to that of the median frequency but was statistically not significant. The upward parabolic task rotation sequence resulted in the lowest fatigue among all the task sequences. Performing intense exertions apart from each other, warm-up exertions, and the presence of active recovery after the intense exertions could be the factors that produced the lowest fatigue during this sequence.

Risk of pain in the neck and shoulders and job change among hairdressers: a combined questionnaire and register-based Danish prospective cohort study

Objective

To investigate whether intensity of work as a hairdresser was associated with treatments for pain, and if musculoskeletal pain was associated with leaving the hairdressing trade.

Methods

We formed two cohorts of hairdressers covered in the PensionDanmark Health Scheme (PDHS). Cohort 1 consisted of 1304 active hairdressers in 2009. Self-reported weekly haircuts were used as work intensity measure and treatments for pain in the neck and shoulders in PDHS were used as outcome. We used a Cox regression model with robust sandwich estimates adjusted for age, sex, employment status and prior treatment < 1 year before July 2009. Cohort 2 consisted of all hairdressers ever covered in the PDHS from 2006 to 2016 (n = 11,162). Exposure were treatments in PDHS within the last year. Outcome was leaving the trade within the following year. Adjustments were made for sex, calendar-year and age in Cox regression models.

Results

The adjusted hazard ratio of treatments in PDHS compared to the lowest work intensity was 0.95 (95% CI 0.58–1.55) and 0.74 (0.43–1.29) for medium and highest intensity, respectively. The risk of leaving the trade was lower, HR 0.80 (0.72–0.90) among hairdressers with treatments in PDHS within the last year, mainly driven by hairdressers aged < 56 years.

Conclusion

We found no association between intensity of work as a hairdresser, measured as self-reported weekly haircuts, and treatments for pain in PDHS. Furthermore, we found a protective effect of treatments in the PDHS within the last year on risk of leaving the trade.

Effects of Sensor Types and Angular Velocity Computational Methods in Field Measurements of Occupational Upper Arm and Trunk Postures and Movements

Accelerometer-based inclinometers have dominated kinematic measurements in previous field studies, while the use of inertial measurement units that additionally include gyroscopes is rapidly increasing. Recent laboratory studies suggest that these two sensor types and the two commonly used angular velocity computational methods may produce substantially different results. The aim of this study was, therefore, to evaluate the effects of sensor types and angular velocity computational methods on the measures of work postures and movements in a real occupational setting. Half-workday recordings of arm and trunk postures, and movements from 38 warehouse workers were compared using two sensor types: accelerometers versus accelerometers with gyroscopes-and using two angular velocity computational methods, i.e., inclination velocity versus generalized velocity. The results showed an overall small difference (<2° and value independent) for posture percentiles between the two sensor types, but substantial differences in movement percentiles both between the sensor types and between the angular computational methods. For example, the group mean of the 50th percentiles were for accelerometers: 71°/s (generalized velocity) and 33°/s (inclination velocity)-and for accelerometers with gyroscopes: 31°/s (generalized velocity) and 16°/s (inclination velocity). The significant effects of sensor types and angular computational methods on angular velocity measures in field work are important in inter-study comparisons and in comparisons to recommended threshold limit values.

Work-related musculoskeletal disorders and associated risk factors among urban metropolitan hairdressers in India

Objectives

Ergonomic hazards account for a substantial proportion of work‐related diseases and injuries among hairdressers. Awkward posture during work, repetitive movements, prolonged standing, and long working periods to carry out work activities cause mechanical load on the joints and work‐related musculoskeletal disorders (WMSDs). This study investigated the musculoskeletal problems among urban hairdressers and associated risk factors.

Methods

This study investigates the prevalence of WMSDs among 768 study subjects (384 hairdressers and control subjects each) from Ahmedabad and New Delhi metropolis in India. Univariate statistical analysis was carried out along with 95% confidence interval for effect estimates.

Results

Findings reveal that the nearly half of the hairdressers suffered from knee and foot pain (49.5%), followed by lower back pain (39.8%) and upper back pain (38.8%). The neck pain and shoulder pain were reported by more than 25% hairdressers. The odds of developing neck pain (OR = 2.04; 95% CI 1.37‐3.06) and shoulder pain (OR = 1.85; 95% CI 1.25‐2.73) were significantly higher than control. The female hairdressers were more likely to experience work‐related musculoskeletal disorder (OR = 2.63; 95% CI 1.18‐5.86) than male counterparts. Hairdressers within the age of 18‐35 years had significantly higher occurrence of musculoskeletal disorders with longer duration of working hours at the workplace. Longer daily work hours (>12 hours) posed significantly higher risk (OR = 2.47; 95% CI 1.39‐4.38) of experiencing MSD for hairdressers.

Conclusion

A very large proportion of hairdressers suffered with work‐related musculoskeletal disorders. The long daily working hours and gender of the hairdresser are associated with increased risk of developing WMSDs.

Development and validation of a cumulative exposure shoulder risk assessment tool based on fatigue failure theory

OBJECTIVE

To present a new risk assessment tool for shoulder intensive occupational tasks based on fatigue failure theory.

METHODS

The tool estimates cumulative damage (CD) based on shoulder moments and loading cycles using an S-N curve derived from in vitro tendon fatigue failure tests. If multiple shoulder tasks are performed, the CD for each is summed. In the validation, 293 workers were evaluated for five separate shoulder outcomes. Logistic regression was used to assess the log CD against five shoulder outcomes adjusted for covariates including age, sex, body mass index (BMI), and plant site.

RESULTS

Both crude and adjusted logistic regression results demonstrated strong dose-response associations between the log CD measure and all five shoulder outcomes (continuous ORs ranged from 2.12 to 5.20).

CONCLUSIONS

The CD measure of The Shoulder Tool demonstrated dose-response relationships with multiple health outcomes. This provides further support that MSDs may be the result of a fatigue failure process.

PRACTITIONER SUMMARY

This study presents a new, easy-to-use risk assessment tool for occupational tasks involving stressful shoulder exertions. The tool is based on fatigue failure theory. The tool was tested against an existing epidemiology study and demonstrated strong relationships to multiple shoulder outcomes.

ABBREVIATIONS

MSD: musculoskeletal disorder; NORA: national occupational research agenda; RULA: rapid upper limb assessment; REBA: rapid entire body assessment; S-N: stress-number of cycles; EDL: extensor digitorum longus; DPC: damage per cycle; CD: cumulative damage; UTS: ultimate tensile strength; FTOV: first time office visit; 3DSSPP: 3-dimensional static strength prediction program; AS: visual analogue scale; BMI: body mass index; CI: confidence interval; Nm: newton-metre; LiFFT: lifting fatigue failure tool; DUET: distal upper extremity tool; OMNI-RES: OMNI resistance exercise scale.

Can a metric combining arm elevation and trapezius muscle activity predict neck/shoulder pain? A prospective cohort study in construction and healthcare

OBJECTIVE

To determine whether a composite metric of arm elevation and trapezius activity (i.e. neck/shoulder load) is more strongly associated with the 2-year course of neck and shoulder pain intensity (NSPi) among construction and healthcare workers than each exposure separately.

METHODS

Dominant arm elevation and upper trapezius muscle activity were estimated in construction and healthcare employees (n = 118) at baseline, using accelerometry and normalized surface electromyography (%MVE), respectively. At baseline and every 6 months for 2 years, workers reported NSPi (score 0-3). Compositions of working time were determined for arm elevation (< 30°; 30-60°;  > 60°), trapezius activity (< 0.5%; 0.5-7.0%; > 7.0%MVE), and a composite metric "neck/shoulder load" (restitution, low, medium, and high load). Associations between each of these three compositions and the 2-year course of NSPi were determined using linear mixed models.

RESULTS

Associations between exposure compositions and the course of NSPi were all weak and in general uncertain. Time spent in 0.5-7.0%MVE showed the largest and most certain association with changes in NSPi during follow-up (β = - 0.13; p = 0.037; corresponding to a -0.01 change in NPSi every 6 months). Among pain-free workers at baseline, medium (β = - 0.23; p = 0.039) and high (β = 0.15; p = 0.031) neck/shoulder load contributed the most to explaining changes in NSPi.

CONCLUSION

The composite metric of neck/shoulder load did not show a stronger association with the course of NSPi than arm elevation or trapezius activity alone in the entire population, while some indications of a stronger association were found among those who were pain-free at baseline.

Work above shoulder level and shoulder complaints: a systematic review

OBJECTIVE

To investigate the association and the exposure-response relationship between work above shoulder height and shoulder pain or disorders.

METHODS

A systematic search was performed in Medline, Embase, and Health and Safety Science Abstracts. Included were articles with prospective cohort, case-control, cross-sectional, or intervention study designs. Quality assessment was based on an evaluation scheme adjusted to study design and normalized to 100%. The cut-off for sufficient quality to include articles was above 40% and cut-off for high-quality articles was above 50% of maximal score. The level of strength of evidence for an association between exposure and effect was assessed according to the GRADE guidelines.

RESULTS

Thirty-four articles were included. Articles that document large effects (higher risk estimates; OR ≥ 2) have higher quality score, include analyses of severe arm elevation, more often use clinical outcome, and report an exposure-response relationship compared to studies reporting lower risk estimates. The studies that reported large effects were all significant. An exposure-response relationship was found in many high-quality studies when relating exposure intensity of arm elevation (level of arm elevation, amplitude) as well as duration of arm elevation, especially > 90°.

CONCLUSION

We conclude on a limited evidence for an association between arm elevation at work and shoulder disorders. Severe arm elevation with elbows above shoulder level (i.e., > 90°) shows a moderate evidence for an association with shoulder disorders.

Musculoskeletal health, work-related risk factors and preventive measures in hairdressing: a scoping review

BACKGROUND

Hairdressers are exposed to various work-related biomechanical and organizational risk factors. To date, there has been no overview of the evidence for this occupational group. The purpose of this scoping review is to gain insight into the current state of research on work-related musculoskeletal disorders (MSD) in hairdressing.

METHODS

Studies published up to November 2018 were identified by a systematic search using electronic databases (MEDLINE, PUBMED, CINAHL, Web of Science, LIVIVO), Google Scholar and reference lists of articles. Studies were screened by two researchers and synthesized in a descriptive manner.

RESULTS

Overall 44 studies with different study designs, scopes and approaches were included. Nineteen studies provided data on MSD prevalence in at least one body site. The prevalence values between the studies varied considerably. On average, the highest 12-month prevalence was reported for the lower back (range 13-76%), neck (range 9-58%), shoulder (range 28-60%) and hand/wrist (range 11-53%). In comparison to other occupational groups, hairdressers reported more frequent MSD in all body regions or exhibited a greater risk of leaving the profession for health reasons. Common risk factors include working with arms above shoulder level, repetitive movements, forceful exertion of upper extremities, awkward back postures and movements, high mechanical workload and standing. In addition to physical stress, lack of adequate breaks, overtime, and general distress may deteriorate health and performance of hairdressers. Three rehabilitative and three preventive interventional studies were found. Only the rehabilitative studies showed positive effects on the management of physical and mental strain and resulted in significant pain reduction, increased physical capacity and knowledge of potential risk factors for MSD.

CONCLUSION

This data provides some evidence for work-related risk factors for MSD in hairdressers and indicate that there should be an intense focus on preventive measures. High quality and long-term interventional studies are needed to clarify the effectiveness of complex preventive concepts in hairdressing.

Exposure to Upper Arm Elevation During Work Compared to Leisure Among 12 Different Occupations Measured with Triaxial Accelerometers

Regarding prevention of neck and shoulder pain (NSP), unsupported arm elevation is one factor that should be taken into account when performing work risk assessment. Triaxial accelerometers can be used to measure arm elevation over several days but it is not possible to differentiate between supported and unsupported arm elevation from accelerometers only. Supported arm elevation is more likely to exist during sitting than standing. The aim of the study was to evaluate the use of whole workday measurements of arm elevation with accelerometers to assess potentially harmful work exposure of arm elevation, by comparing arm elevation at work with arm elevation during leisure, in a population with diverse work tasks, and to assess how the exposure parameters were modified when upper arm elevation during sitting time was excluded. The participants, 197 workers belonging to 12 occupational groups with diverse work tasks, wore triaxial accelerometers on the dominant arm, hip, and back for 1–4 days to measure arm elevation and periods of sitting. None of the groups were found to have higher exposure to arm elevation during work compared to leisure. Even though some occupations where known to have work tasks that forced them to work with elevated arms to a large extent. A high proportion of arm elevation derived from sitting time, especially so during leisure. When arm elevation during sitting time was excluded from the analysis, arm elevation was significantly higher at work than during leisure among construction workers, garbage collectors, manufacturing workers, and domestic cleaners. Together this illustrates that it is not suitable to use whole workday measurments of arm elevation with accelerometer as a sole information source when assessing the risk for NSP due to arm elevation. Information on body posture can provide relevant contextual information in exposure assessments when it is known that the potential harmful exposure is performed in standing or walking.

Validity of Wearable Sensors at the Shoulder Joint: Combining Wireless Electromyography Sensors and Inertial Measurement Units to Perform Physical Workplace Assessments

Background: Workplace adaptation is the preferred method of intervention to diminish risk factors associated with the development of work-related shoulder disorders. However, the majority of the workplace assessments performed are subjective (e.g., questionnaires). Quantitative assessments are required to support workplace adaptations. The aims of this study are to assess the concurrent validity of inertial measurement units (IMUs; MVN, Xsens) in comparison to a motion capture system (Vicon) during lifting tasks, and establish the discriminative validity of a wireless electromyography (EMG) system for the evaluation of muscle activity. Methods: Sixteen participants performed 12 simple tasks (shoulder flexion, abduction, scaption) and 16 complex lifting tasks (lifting crates of different weights at different heights). A Delsys Trigno EMG system was used to record anterior and middle deltoids’ EMG activity, while the Xsens and Vicon simultaneously recorded shoulder kinematics. Results: For IMUs, correlation coefficients were high (simple task: >0.968; complex task: >0.84) and RMSEs were low (simple task: <6.72°; complex task: <11.5°). For EMG, a significant effect of weight, height and a weight x height interaction (anterior: p < 0.001; middle: p < 0.03) were observed for RMS EMG activity. Conclusions: These results suggest that wireless EMG and IMUs are valid units that can be used to measure physical demand in workplace assessments.

Characterizing exposure to physical risk factors among reforestation hand planters in the Southeastern United States

Low back and neck/shoulder pain are commonly reported among reforestation hand planters. While some studies have documented the intensive cardiovascular demands of hand planting, limited information is available regarding exposures to physical risk factors associated with the development of musculoskeletal disorders (MSDs) among hand planters. This study used surface electromyography (EMG) and inertial measurement units (IMUs) to characterize the muscle activation patterns, upper arm and trunk postures, movement velocities, and physical activity (PA) of fourteen Southeastern reforestation hand planters over one work shift. Results indicated that hand planters are exposed to physical risk factors such as extreme trunk postures (32.5% of time spent in ≥45° trunk flexion) and high effort muscle exertions (e.g., mean root-mean-square right upper trapezius amplitude of 54.1% reference voluntary exertion) that may place them at increased risk for developing MSDs. The findings indicate a need for continued field-based research among hand planters to identify and/or develop maximally effective interventions.

Association of objectively measured arm inclination with shoulder pain: A 6-month follow-up prospective study of construction and health care workers

OBJECTIVES

The aim was to determine the association of occupational arm inclination with shoulder pain in construction and health care workers.

METHODS

Arm inclination relative to the vertical was measured with an accelerometer placed on the dominant upper arm for up to four full days at baseline in 62 construction workers and 63 health care workers. The pain intensity in the shoulder and mechanical and psychosocial work factors were measured by self-reports at baseline and prospectively after 6 months. The associations between exposures and shoulder pain were analyzed with multilevel mixed-effects linear regressions.

RESULTS

For the total study population working with the dominant arm at inclinations > 30° and >120° was associated with lower levels of shoulder pain both cross-sectionally and after 6 months. Associations were attenuated when adjusting for individual and social factors, psychological state, and exposure during leisure time, especially for the high inclination levels. Analyses, only including subjects with no pain at baseline revealed no significant associations. While stratified analysis showed negative associations in the construction worker group, there were no significant association in health care workers. Compared to the number of hypotheses tested, the number of significant findings was low. Adjustment by Bonferroni-correction made almost all findings insignificant.

CONCLUSIONS

All analyses reflected a negative association between arm inclination and shoulder pain, but few analyses showed these associations to be statistically significant. If there is a relationship between arm inclination and shoulder pain, these findings could indicate that pain-avoidance may modify how workers perform their tasks.

Predicted endurance times during overhead work: influences of duty cycle and tool mass estimated using perceived discomfort

A need for overhead work remains in several industries and such work is an important risk factor for shoulder musculoskeletal problems. In this study, we evaluated the effects of duty cycle and tool mass on endurance times during overhead work. A psychophysical approach was used, via a new methodology that was implemented to more efficiently estimate endurance times (rather than through direct measurements). Participants performed a simulated overhead task in specified combinations of tool mass and duty cycle. Both duty cycle and tool mass have substantial effects on the development of fatigue and estimated endurance times, though the former was more substantial and an interactive effect was evident. Gender differences were not substantial, except when using the largest tool mass. We recommend that, for two-hour periods of overhead work, tool masses greater than 1.25 kg should be avoided, as should duty cycles greater than 50%. Practitioner Summary: The current results may facilitate enhanced design and evaluation of overhead work tasks. In addition, the new estimation approach that was employed may enhance the efficiency of future studies using a psychophysical approach (ie using extrapolation of patterns of reported discomfort to predict longer term outcomes).

Evaluation of upper body kinematics and muscle activity during milking attachment task

The objective of the study was to evaluate the effects of udder height on upper body kinematics and muscle activity during a simulated attachment task in a parallel parlor set up, and the effects of udder access method (back or side) on the task biomechanics. Twenty males performed the task under conditions that simulated three udder heights and two udder access methods. The muscular load and kinematics during the task confirmed that milking is a physically demanding task. Trunk flexion angle increased with decreasing udder height, and the erector spinae activation was higher when the udder was below shoulder height compared to at or above. Compared to accessing the udder from side of the cow (herringbone parlor style), accessing from behind (Parallel parlor style) was associated with lower trunk flexion, greater shoulder horizontal adduction, lower shoulder elevation, and greater anterior deltoid activation. Milking in herringbone parlor style and with the udder at or above shoulder level may help reduce strain on the trunk/neck.

Longitudinal study exploring factors associated with neck/shoulder pain at 52 years of age

OBJECTIVES

To investigate the ability of work-related measurements, body composition, physical activity, and fitness levels to predict neck/shoulder pain (upper body pain, UBP) at the age of 52 years. Another aim was to investigate the cross-sectional relationships between UBP, work-related factors, and individual factors at the age of 52 years.

METHODS

We followed a randomly selected cohort of 429 adolescents that was recruited in 1974 (baseline), when they were 16 years old. The participants completed physical fitness tests, questions about sociodemographic and lifestyle factors at 16, 34, and 52 years of age, and questions about work-related factors and pain in the follow-ups. Logistic regression analyses were used to examine the associations between UBP and the other variables.

RESULTS

Univariate logistic regression analyses showed that high body mass index and the work-related factors, low control, and low social support at the age of 34 years were related to UBP at the age of 52 years. For social support, there was an interaction between men and women where the relationship between low social support and the experience of pain was more evident for women. Among women, body mass index and social support remained significantly related in the multivariate analyses. For men, social support remained significantly related. Cross-sectional relationships at the age of 52 differed from the longitudinal in the sense that measures of joint flexibility and work posture were also significantly associated with UBP.

CONCLUSION

The fact that the cross-sectional differed from the longitudinal relationships strengthens the importance of performing longitudinal studies when studying factors that might influence the initiation of pain. UBP preventative measures might need to include both lifestyle (such as dietary habits and physical activity to ensure that the individuals are not becoming overweight) and work-related factors such as social support.

Working postures and physical activity among registered nurses

Nurses report a high prevalence of musculoskeletal discomfort, particularly of the low back and neck/shoulder. This study characterized the full-shift upper arm and trunk postures and movement velocities of registered nurses using inertial measurement units (IMUs). Intensity of occupational physical activity (PA) was also ascertained using a waist-worn PA monitor and using the raw acceleration data from each IMU. Results indicated that nurses spent a relatively small proportion of their work time with the arms or trunk in extreme postures, but had few opportunities for rest and recovery in comparison to several other occupational groups. Comparisons between nurses in different PA groups suggested that using a combination of accelerometers secured to several body locations may provide more representative estimates of physical demands than a single, waist-worn PA monitor. The findings indicate a need for continued field-based research with larger sample sizes to facilitate the development of maximally effective intervention strategies.