Risk of musculoskeletal disorders among females and males in repetitive/constrained work

Sex differences in kinematic adaptations to muscle fatigue induced by repetitive upper limb movements

Background

Muscle fatigue induced by repetitive movements contributes to the development of musculoskeletal disorders. Men and women respond differently to muscle fatigue during isometric single-joint efforts, but sex differences during dynamic multi-joint tasks have not been clearly identified. Moreover, most studies comparing men and women during fatigue development assessed endurance time. However, none evaluated sex differences in kinematic adaptations to fatigue during multi-joint dynamic tasks. The objective of the study was to compare how men and women adapt their upper body kinematics during a fatiguing repetitive pointing task.

Methods

Forty men and 41 women performed repetitive pointing movements (one per second) between two targets while maintaining their elbow elevated at shoulder height. The task ended when participants rated a perceived level of fatigue of 8/10. Trunk, humerothoracic, and elbow angles were compared between the first and last 30 s of the experiment and between men and women. Linear positions of the index finger (distance from the target) and the elbow (arm elevation) as well as movement timing were documented as task performance measures.

Results

Men (7.4 ± 3.2 min) and women (8.3 ± 4.5 min) performed the repetitive pointing task for a similar duration. For both sex groups, trunk range of motion increased with fatigue while shoulder’s and elbow’s decreased. Moreover, participants modified their trunk posture to compensate for the decreased humerothoracic elevation. Movements at all joints also became more variable with fatigue. However, of the 24 joint angle variables assessed, only two Sex × Fatigue interactions were observed. Although average humerothoracic elevation angle decreased in both subgroups, this decrease was greater in men (standardized response mean [SRM] − 1.63) than in women (SRM − 1.44). Moreover, the movement-to-movement variability of humerothoracic elevation angle increased only in women (SRM 0.42).

Conclusion

Despite many similarities between men’s and women’s response to fatigue induced by repetitive pointing movements, some sex differences were observed. Those subtle differences may indicate that men’s shoulder muscles were more fatigued than women’s despite a similar level of perceived exertion. They may also indicate that men and women do not adapt the exact same way to a similar fatigue.

Electronic supplementary material

The online version of this article (10.1186/s13293-018-0175-9) contains supplementary material, which is available to authorized users.

Work-Related Biomechanical Exposure and Job Strain as Separate and Joint Predictors of Musculoskeletal Diseases: A 28-Year Prospective Follow-up Study

We investigated how work-related biomechanical exposure and job strain in midlife separately and jointly predicted back and degenerative musculoskeletal diseases (MSDs). A total of 6,257 employees participated in the Finnish Longitudinal Study on Aging Municipal Employees (FLAME) in 1981 and were followed up for 28 years. Risk ratios and the relative excessive risk due to interaction and 95% confidence intervals were modeled for separate and joint prediction estimates, respectively. After adjustment for confounders, job strain predicted degenerative MSDs among women after 4 and 11 years of follow-up. After 11 years, both exposures predicted both types of MSDs among men. Joint exposure predicted both types of MSDs after 4 years among women (for back MSDs, risk ratio (RR) = 1.58, 95% confidence interval (CI): 1.15, 2.18; for degenerative MSDs, RR = 1.59, 95% CI: 1.21, 2.07) and men (for back MSDs, RR = 1.50, 95% CI: 1.05, 2.15; for degenerative MSDs, RR = 1.61, 95% CI: 1.16, 2.22) and both types of MSDs after 11 years (for back MSDs, RR = 1.72, 95% CI: 1.21, 2.43; for degenerative MSDs, RR = 1.68, 95% CI: 1.25, 2.46) among men only, but the relative excessive risk due to interaction was not significant throughout. However, after 28 years, the separate and joint exposures did not predict MSDs. Workplace interventions should be focused on reducing job strain along with biomechanical exposure for possible prevention of MSDs in working life and around the time of retirement, but there may be other pathways of onset of MSDs in old age.

Arthroscopic surgical treatment of medial epicondylitis

BACKGROUND

The study purpose was to evaluate the outcomes of patients who received arthroscopic surgical treatment for medial epicondylitis refractory to conservative treatment.

METHODS

This was a retrospective study of 7 patients who underwent arthroscopic surgical débridement of the common flexor tendon for treatment of medial epicondylitis refractory to conservative treatment. The patients were assessed using the Disabilities of the Arm, Shoulder and Hand score; visual analog scale for pain; and Short Form 36 Health Survey. The mean age at the time of surgery was 50 years (range, 36-67 years). The mean duration of symptoms before surgery was approximately 2 years (range, 8 months to 4 years). The mean follow-up duration was 17 months (range, 6-48 months).

RESULTS

The average postoperative scores were 17 points on the Disabilities of the Arm, Shoulder and Hand outcome measure; 2 points on the visual analog scale at rest for 6 subjects (86%) with slight pain and 1 (14%) with moderate pain; and 78 on the Short Form 36 Health Survey. No significant complications were observed when the procedure was performed via arthroscopy.

CONCLUSION

Arthroscopic surgical treatment for medial epicondylitis of the elbow exhibits good outcomes and is safe and effective.

Full shift assessment of back and head postures in overhead crane operators with and without symptoms

OBJECTIVES

Prolonged sitting with a flexed back and neck is recognized as being associated with an increased risk of neck and back pain disorders among overhead crane operators. The aim of this study was to compare back and head postures over a full shift of work between operators who experience back and neck pain, and healthy operators.

METHODS

In a first phase, the prevalence of musculoskeletal symptoms was assessed using the Nordic questionnaire among 120 crane operators. Based on first phase results, 17 operators with back/neck disorders were matched with 15 healthy operators based on age and selected to participate in the second phase of the study. Postures and movements were continuously measured over an 8 h shift using inclinometers.

RESULTS

The highest 12-month prevalence of musculoskeletal disorders was found in the lower back, neck and knees. Case and control groups differed significantly in back and head flexion angles at the 50th percentiles APDF (p < 0.05). There was also a significant difference in the time spent working in an extreme posture of the back and head between groups (p < 0.05).

CONCLUSIONS

This is the first study to document work postures assumed during a full work shift and to compare postures between symptomatic and healthy overhead crane operators. Physical exposure in case group operators was characterized by more awkward and extreme postures in the back and head. The results of this study demonstrate that effective prevention strategies directed towards musculoskeletal disorders are required that address awkward work postures for overhead crane operators.

Work-related risk factors for specific shoulder disorders: a systematic review and meta-analysis

The objective of this systematic review and meta-analysis is to examine which work-related risk factors are associated with specific soft tissue shoulder disorders. We searched the electronic databases of Medline and Embase for articles published between 2009 and 24 March 2016 and included the references of a systematic review performed for the period before 2009. Primary cross-sectional and longitudinal studies were included when outcome data were described in terms of clinically assessed soft tissue shoulder disorders and at least two levels of work-related exposure were mentioned (exposed vs less or non-exposed). Two authors independently selected studies, extracted data and assessed study quality. For longitudinal studies, we performed meta-analyses and used GRADE (Grades of Recommendations, Assessment, Development and Evaluation) to assess the evidence for the associations between risk factors and the onset of shoulder disorders. Twenty-seven studies met the inclusion criteria. In total, 16 300 patients with specific soft tissue shoulder disorders from a population of 2 413 722 workers from Denmark, Finland, France, Germany and Poland were included in the meta-analysis of one case-control and six prospective cohort studies. This meta-analysis revealed moderate evidence for associations between shoulder disorders and arm-hand elevation (OR=1.9, 95% CI 1.47 to 2.47) and shoulder load (OR=2.0, 95% CI 1.90 to 2.10) and low to very low evidence for hand force exertion (OR=1.5, 95% CI 1.25 to 1.87), hand-arm vibration (OR=1.3, 95% CI 1.01 to 1.77), psychosocial job demands (OR=1.1, 95% CI 1.01 to 1.25) and working together with temporary workers (OR=2.2, 95% CI 1.2 to 4.2). Low-quality evidence for no associations was found for arm repetition, social support, decision latitude, job control and job security. Moderate evidence was found that arm-hand elevation and shoulder load double the risk of specific shoulder disorders. Low to very-low-quality evidence was found for an association between hand force exertion, hand-arm vibration, psychosocial job demands and working together with temporary workers and the incidence of specific shoulder disorders.

Upper extremity disorders in heavy industry workers in Greece

AIM

To investigate the disability due to musculoskeletal disorders of the upper extremities in heavy industry workers.

METHODS

The population under study consisted of 802 employees, both white- and blue-collar, working in a shipyard industry in Athens, Greece. Data were collected through the distribution of questionnaires and the recording of individual and job-related characteristics during the period 2006-2009. The questionnaires used were the Quick Disabilities of the Arm, Shoulder and Hand (QD) Outcome Measure, the Work Ability Index (WAI) and the Short-Form-36 (SF-36) Health Survey. The QD was divided into three parameters - movement restrictions in everyday activities, work and sports/music activities - and the SF-36 into two items, physical and emotional. Multiple linear regression analysis was performed by means of the SPSS v.22 for Windows Statistical Package.

RESULTS

The answers given by the participants for the QD did not reveal great discomfort regarding the execution of manual tasks, with the majority of the participants scoring under 5%, meaning no disability. After conducting multiple linear regression, age revealed a positive association with the parameter of restrictions in everyday activities (b = 0.64, P = 0.000). Basic education showed a statistically significant association regarding restrictions during leisure activities, with b = 2.140 (P = 0.029) for compulsory education graduates. WAI’s final score displayed negative charging in the regression analysis of all three parameters, with b = -0.142 (P = 0.0), b = -0.099 (P = 0.055) and b = -0.376 (P = 0.001) respectively, while the physical and emotional components of SF-36 associated with movement restrictions only in daily activities and work. The participants’ specialty made no statistically significant associations with any of the three parameters of the QD.

CONCLUSION

Increased musculoskeletal disorders of the upper extremity are associated with older age, lower basic education and physical and mental/emotional health and reduced working ability.

The spatial dependency of shoulder muscular demands during upward and downward exertions

Lifting and lowering are common occupational tasks contributing to shoulder injury risk. Quantifying task interaction with physical demand can precipitate better workstation designs. Nineteen university-aged males performed one-handed, submaximal upward/downward manual force exertions at 70 hand locations; unilateral electromyography (EMG) of 14 muscles was recorded. EMG across planes was evaluated with ANOVA. Predictive equations for muscle activity throughout the reach envelope were developed with stepwise regression. Total muscle activity (sum of individual muscle activity) was most sensitive to vertical hand location for upward exertions, where activation at superior locations was 192% of values for inferior locations. For upward exertions, activation differences for hand location occurred along all anatomical axes, and along anterior/posterior and superior/inferior axes for downward exertions. Predictive equations were non-linear, reflecting complex muscular demand with three-dimensional hand location. This work details foundational exposure data for lifting/lowering exertions. Results are applicable to workstation design to minimise occupational shoulder muscular demands. Practitioner Summary: Lifting and lowering in the workplace contribute to shoulder injury risk. Shoulder muscle activity magnitudes revealed a dependence on three-dimensional hand location in the reach envelope for a defined hand force. This information can inform evidence-based workstation designs that reduce shoulder muscular demands for numerous materials handling scenarios.

Opting to wear prismatic spectacles was associated with reduced neck pain in dental personnel: a longitudinal cohort study

Background

The aim of this study was to investigate effects on perceived exertion, work ability self-reported neck pain and clinically diagnosed conditions in the neck, of an intervention with prismatic spectacles among dental personnel.

Methods

In this cohort study a baseline questionnaire including questions about frequency of neck pain, perceived exertion during work and background information was distributed to dental personnel in municipal dental care units. In connection, personnel from 78 out of 110 dental care units underwent a clinical neck examination and rated their perceived work ability with the single-item question from the Work Ability Index. The study population consisted of 564 participants; 366 in the questionnaire group, 321 in the examination group, whereof 123 participated in both assessments. In total 371 belonged to the intervention group and received individually adjusted prismatic spectacles after the baseline assessments (inclusion based on self-selection) and 193 belonged to the reference group. At the 12-month follow-up the clinical examination was repeated and the same questionnaire with additional questions was completed. Fisher’s exact test or the Mann–Whitney U test was used to assess differences between the intervention group and the reference group at baseline. Differences at follow up between the two groups were assessed by means of Linear-by Linear association test for trends.

Results

A significant decrease in neck pain (p = 0.047), clinical diagnoses in the neck (p = 0.025), and perceived exertion (p = 0.003) was observed at follow up for the intervention group compared to the reference group. Moreover, for the intervention group a significantly improved self-rated work ability (p = 0.040) was reported. Finally, opting to wear prismatic spectacles during dental work appeared to have a preventive effect on neck pain.

Conclusions

Dental personnel opting to wear prismatic spectacles reduced their neck pain significantly more at follow up compared with the reference group. These results are worthwhile testing in a randomised design. The practical implication of this study is that recommendations regarding ergonomics for dental professionals may include the use of prismatic glasses, both as primary and secondary prevention of work-related neck pain. Such glasses should also be tested in other working situations where the work tasks include high visual demands in sustained awkward neck postures.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-016-1145-1) contains supplementary material, which is available to authorized users.

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.

Validity of a small low-cost triaxial accelerometer with integrated logger for uncomplicated measurements of postures and movements of head, upper back and upper arms

Repetitive work and work in constrained postures are risk factors for developing musculoskeletal disorders. Low-cost, user-friendly technical methods to quantify these risks are needed. The aims were to validate inclination angles and velocities of one model of the new generation of accelerometers with integrated data loggers against a previously validated one, and to compare meaurements when using a plain reference posture with that of a standardized one. All mean (n = 12 subjects) angular RMS-differences in 4 work tasks and 4 body parts were <2.5° and all mean median angular velocity differences <5.0 °/s. The mean correlation between the inclination signal-pairs was 0.996. This model of the new generation of triaxial accelerometers proved to be comparable to the validated accelerometer using a data logger. This makes it well-suited, for both researchers and practitioners, to measure postures and movements during work. Further work is needed for validation of the plain reference posture for upper arms.

Early retirement among Danish female cleaners and shop assistants according to work environment characteristics and upper extremity complaints: an 11-year follow-up study

Background

Studies have shown a negative social gradient in the incidence of early retirement. To prevent undesired early retirement, there is a need for knowledge of specific predictors in addition to social factors with a limited potential for change. The main purpose of this study was to examine musculoskeletal complaints and working conditions as predictors of early retirement among Danish female cleaners.

Methods

Using Cox regression with an adjustment for extraneous factors, we compared the risk of disability pension and retirement before the nominal retirement age (65 years) in an 11-year cohort study with registry-based follow-up of 1430 female cleaners and 579 shop assistants. In subsequent analyses of female cleaners, disability pension and voluntary early retirement were modeled according to work characteristics and upper extremity complaints.

Results

The adjusted hazard rate (HR) for disability pension among cleaners compared to the control group was 2.27 (95 % CI 1.58 to 3.28) and, for voluntary early retirement, 1.01 (95 % CI 0.85 to 1.20). In the subset of cleaners, the predictors of disability pension were persistent shoulder pain HR: 1.98 (95 % CI 1.47 to 2.67), elbow pain HR: 1.41 (95 % CI 1.02 to 1.94) and symptoms of nerve entrapment of the hand HR: 1.58 (95 % CI 1.14 to 2.20). Predictors of voluntary early retirement were persistent shoulder pain HR: 1.40 (95 % CI 1.16 to 1.67) and floor mopping for more than 10 h per week HR: 1.20 (95 % CI 1.03 to 1.40).

Conclusion

Cleaners have a twofold higher risk of disability pension compared to the control group. Risk factors for disability pension among cleaners were persistent shoulder and elbow pain together with symptoms of nerve entrapment of the hand. The findings of specific health related predictors of early retirement could be used in secondary prevention with targeted temporary reduced workload.

Prevalence of musculoskeletal disorders among immigrant Latino farmworkers and non-farmworkers in North Carolina

This paper evaluates the variability in the prevalence of epicondylitis, rotator cuff syndrome, low back pain, and lower extremity pathology among immigrant Latino farmworkers and non-farmworkers. Data were collected from a study among 272 farmworkers and non-farmworkers. Participants were recruited in eastern and central North Carolina. A physical examination was conducted by trained physicians. Prevalence of musculoskeletal disorders (MSDs) among Latino manual workers is high compared with other workers in similar occupations. Non-farmworkers (49%) had a higher prevalence of MSDs than farmworkers (35%). Epicondylitis (20.2%) and rotator cuff syndrome (19.1%) were most prevalent. Age was found to be significant among those who had epicondylitis (adjusted odds ratio [AOR] = 1.04) and lower extremity pathology (AOR = 1.07). Latino immigrant manual workers have high prevalence of MSDs. Further studies are needed to identify possible factors that make these populations more vulnerable to MSDs.

Critical review on the socio-economic impact of tendinopathy

There are currently no studies that determine the total burden that tendinopathy places on patients and society. A systematic search was conducted to understand the impact of tendinopathy. It demonstrated that the current prevalence is underestimated, particularly in active populations, such as athletes and workers. Search results demonstrate that due to the high prevalence, impact on patients' daily lives and the economic impact due to work-loss, treatments are significantly higher than currently observed. A well-accepted definition by medical professionals and the public will improve documentation and increase awareness, in order to better tackle the disease burden.

Postural awareness among dental students in Jizan, Saudi Arabia

Objective:

The study was conducted to assess the postural awareness of dental students in Jizan, Saudi Arabia.

Materials and Methods:

Close-ended, self-administered questionnaires were used for data collection in the survey. The questionnaire was prepared by observing the positions of students working in the clinics and the common mistakes they make with regard to their postures. The questionnaires were distributed among the dental students who were present and reported to work in the clinics. Levels of postural awareness and the relationship between postural awareness and the degree of musculoskeletal disorder (MSD) among the students was evaluated. This study was carried out in the College of Dental Sciences and Hospital, Jizan.

Statistical Analysis:

The level of knowledge of postural awareness was evaluated and correlated with the presence or absence of the MSDs. Categorical variables were compared using Chi-square test. P values of less than 0.05 were considered statistically significant.

Results:

A total of 162 dental students from the age group of 20–25 years were included in the survey, of which 134 dentists responded (83%). When their postural awareness was evaluated, results showed that 89% of the students had poor-to-medium levels of postural awareness. The relation between postural awareness and prevalence of MSDs indicated that 75% of the students with poor awareness, 49% of the students with average awareness, and 40% of the students with good awareness have MSDs. The results were statistically significant (0.002127, which is <0.005) stating that better awareness about proper postures while working helps to minimize the risk of MSDs.

Conclusion:

Evaluation of levels of postural awareness showed that 21% of the students had poor postural awareness, 67% had average awareness, and 11% had good postural awareness. The analysis of results showed that those students with low-to-average postural awareness had significantly greater prevalence of MSDs.

The importance of work organization on workload and musculoskeletal health--Grocery store work as a model

We have evaluated the consequences of work organization on musculoskeletal health. Using a postal questionnaire, answered by 1600 female grocery store workers, their main work tasks were identified and four work groups were defined (cashier, picking, and delicatessen work, and a mixed group, who performed a mix of these tasks). The crude odds ratios (ORs) for neck/shoulder complaints were 1.5 (95% CI 1.0-2.2), 1.1 (0.7-1.5) and 1.6 (1.1-2.3), respectively, compared to mixed work. Adjusting for individual and psychosocial factors had no effect on these ORs. For elbows/hands, no significant differences were found. Technical measurements of the workload showed large differences between the work groups. Picking work was the most strenuous, while cashier work showed low loads. Quantitative measures of variation revealed for mixed work high between minutes variation and the highest between/within minutes variation. Combining work tasks with different physical exposure levels increases the variation and may reduce the risk of musculoskeletal complaints.

Musculoskeletal Disorders and Working Posture among Dental and Oral Health Students

The prevalence of musculoskeletal disorders (MSD) in the dental professions has been well established, and can have detrimental effects on the industry, including lower productivity and early retirement. There is increasing evidence that these problems commence during undergraduate training; however, there are still very few studies that investigate the prevalence of MSD or postural risk in these student groups. Thus, the aim of this study was to determine the prevalence of MSD and conduct postural assessments of students studying oral health and dentistry. A previously validated self-reporting questionnaire measuring MSD prevalence, derived from the Standardised Nordic Questionnaire, was distributed to students. Posture assessments were also conducted using a validated Posture Assessment Instrument. MSD was highly prevalent in all student groups, with 85% reporting MSD in at least one body region. The neck and lower back were the most commonly reported. The final year dental students had the highest percentage with poor posture (68%), while the majority of students from other cohorts had acceptable posture. This study supports the increasing evidence that MSD could be developing in students, before the beginning of a professional career. The prevalence of poor posture further highlights the need to place further emphasis on ergonomic education.

Cross-sectional associations between occupational factors and musculoskeletal pain in women teachers, nurses and sonographers

BACKGROUND

It is usually assumed that musculoskeletal pain is associated with both the physical workload and the psychosocial work environment, as well as with personal and lifestyle factors. This study aims to ascertain the prevalence of musculoskeletal pain in women with varying or different occupational exposures, and to explore the associations between musculoskeletal pain and the occupational and personal factors.

METHODS

A questionnaire on physical, psychosocial and individual factors was answered by 1591 women in five occupational groups with contrasting occupational exposures (teachers, anaesthetic, theatre, and assistant nurses, and sonographers). The outcome measure was musculoskeletal pain (in a new model based on frequency and intensity of complaints the preceding year) from the neck, shoulders, hands, lower back and feet.

RESULTS

Neck pain was equally frequent among teachers, assistant nurses and sonographers, and less frequent in anaesthetic and theatre nurses. The sonographers experienced the highest prevalence of shoulder pain, while the assistant nurses were the most affected in the wrists and hands, lower back, and feet. The teachers reported the highest scores in most of the psychosocial dimensions. The theatre nurses scored highest in strenuous work postures and movements (mechanical exposure index, MEI), and the assistant nurses in physical activity and lifting (physical exposure index, PHYI). Multivariable models in the total population showed that both the physical workload and the psychosocial work environment were associated with pain in all body regions, though different factors affected different regions. Pain in the neck, shoulders, hands and lower back was strongly associated with a high MEI and high job demands, while pain in the feet was associated with a high PHYI and a high BMI. A young age was associated with pain in the neck, and an older age was associated with pain in the hands and feet. Lack of time for personal recovery was associated with pain in the shoulders and lower back.

CONCLUSIONS

The occupational groups were affected differently and need different protective measures. For the teachers, the psychosocial work environment should be improved. The surgical staff and sonographers require measures to mitigate lifting and constrained postures.

A better way of fitting clips? A comparative study with respect to physical workload

The clip fitting task is a frequently encountered assembly operation in the car industry. It can cause upper limb pain. During task laboratory simulations, upper limb muscular activity and external force were compared for 4 clip fitting methods: with the bare hand, with an unpowered tool commonly used at a company and with unpowered and powered prototype tools. None of the 4 fitting methods studied induced a lower overall workload than the other three. Muscle activity was lower at the dominant limb when using the unpowered tools and at the non-dominant limb with the bare hand or with the powered tool. Fitting clips with the bare hand required a higher external force than fitting with the three tools. Evaluation of physical workload was different depending on whether external force or muscle activity results were considered. Measuring external force only, as recommended in several standards, is insufficient for evaluating physical workload.

Adaptations to isolated shoulder fatigue during simulated repetitive work. Part II: Recovery

The shoulder allows kinematic and muscular changes to facilitate continued task performance during prolonged repetitive work. The purpose of this work was to examine changes during simulated repetitive work in response to a fatigue protocol. Participants performed 20 one-minute work cycles comprised of 4 shoulder centric tasks, a fatigue protocol, followed by 60 additional cycles. The fatigue protocol targeted the anterior deltoid and cycled between static and dynamic actions. EMG was collected from 14 upper extremity and back muscles and three-dimensional motion was captured during each work cycle. Participants completed post-fatigue work despite EMG manifestations of muscle fatigue, reduced flexion strength (by 28%), and increased perceived exertion (∼3 times). Throughout the post-fatigue work cycles, participants maintained performance via kinematic and muscular adaptations, such as reduced glenohumeral flexion and scapular rotation which were task specific and varied throughout the hour of simulated work. By the end of 60 post-fatigue work cycles, signs of fatigue persisted in the anterior deltoid and developed in the middle deltoid, yet perceived exertion and strength returned to pre-fatigue levels. Recovery from fatigue elicits changes in muscle activity and movement patterns that may not be perceived by the worker which has important implications for injury risk.

Health surveillance under adverse ergonomics conditions--validity of a screening method adapted for the occupational health service

A new health surveillance protocol for work-related upper-extremity musculoskeletal disorders has been validated by comparing the results with a reference protocol. The studied protocol, Health Surveillance in Adverse Ergonomics Conditions (HECO), is a new version of the reference protocol modified for application in the Occupational Health Service (OHS). The HECO protocol contains both a screening part and a diagnosing part. Sixty-three employees were examined. The screening in HECO did not miss any diagnosis found when using the reference protocol, but in comparison to the reference protocol considerable time savings could be achieved. Fair to good agreement between the protocols was obtained for one or more diagnoses in neck/shoulders (86%, k = 0.62) and elbow/hands (84%, k = 0.49). Therefore, the results obtained using the HECO protocol can be compared with a reference material collected with the reference protocol, and thus provide information of the magnitude of disorders in an examined work group. Practitioner Summary: The HECO protocol is a relatively simple physical examination protocol for identification of musculoskeletal disorders in the neck and upper extremities. The protocol is a reliable and cost-effective tool for the OHS to use for occupational health surveillance in order to detect workplaces at high risk for developing musculoskeletal disorders.

Effect of horizontal pick and place locations on shoulder kinematics

In this study the effects of horizontal bin locations in an order picking workstation on upper arm elevation, trunk inclination and hand use were investigated. Eight subjects moved (self-paced) light or heavy products (0.2 and 3.0 kg) from a central product bin to an inner or outer order bin (at 60 or 150 cm) on the left or right side of the workstation, while movements were recorded. The outer compared to inner bin location resulted in more upper arm elevation and trunk inclination per work cycle, both in terms of number of peak values and in terms of time integrals of angles (which is a dose measure over time). Considering the peak values and time integrals per minute (instead of per work cycle), these effects are reduced, due to the higher cycle times for outer bins. Hand use (left, right or both) was not affected by order bin locations.

On physiological demands and sustainability in meat cutting

Meat cutters' work has been investigated by several researchers. However, knowledge about the physiological demands of meat cutting is almost lacking. The aim of this explorative study was to assess physiological demands in meat cutting, to compare them with International Labour Organization (ILO) recommendations for acceptable workload and to discuss the findings in relation to individual and work-related factors. In accordance with the ILO recommendations, work was categorised as sustainable or non-sustainable based on critical relative aerobic strain (RAS) levels. Twenty-one beef and pork cutters participated in the study, which included workload measurements, assessment of workplace and individual factors. Thirteen meat cutters were categorised as having non-sustainable and eight as having sustainable work. Results suggest that the workload is higher in beef cutting than in pork cutting, and that longer work experience is related to lower RAS. Other factors contributing to the physical workload are discussed.

PRACTITIONER SUMMARY

Meat-cutting work may exceed recommended physical workload levels. Beef cutting is physically more demanding than pork cutting. Furthermore, factors such as years in the profession, knife sharpness, work pace, wage system, working technique, maximum oxygen uptake level and muscular strength should be considered when planning actions regarding the workload for meat cutters.

Sex differences in task distribution and task exposures among Danish house painters: an observational study combining questionnaire data with biomechanical measurements

OBJECTIVES

Sex differences in occupational biomechanical exposures may be part of the explanation why musculoskeletal complaints and disorders tend to be more common among women than among men. We aimed to determine possible sex differences in task distribution and task-specific postures and movements of the upper extremities among Danish house painters, and to establish sex-specific task exposure matrices.

METHODS

To obtain task distributions, we sent out a questionnaire to all members of the Painters' Union in Denmark (N = 9364), of whom 53% responded. Respondents reported their task distributions in a typical week. To obtain task exposures, postures and movements were measured in 25 male and 25 female house painters for one whole working day per person. We used goniometers on the wrists, and inclinometers on the forehead and the upper arms. Participants filled in a logbook allowing task-specific exposures to be identified. Percentiles and % time with non-neutral postures were used to characterise postures. Velocity, range of motion, repetitiveness, and variation were used as measures of movement. Cochran-Mantel-Haenszel statistics and unpaired double-sided t-tests with post-hoc Bonferroni correction were used to evaluate sex differences.

RESULTS

Statistically significant (p<0.05) sex differences were revealed in task proportions, but the proportions differed by less than 4%. For task exposures, no statistically significant sex differences were found.

CONCLUSIONS

Only minor sex differences were found in task distribution and task exposures regarding postures and movements among Danish house painters. Sex-specific task exposure matrices were established.

Employer differences in upper-body musculoskeletal disorders and pain among immigrant Latino poultry processing workers

Between-employer differences in working conditions may lead to variable injury rates. The objective of this paper is to assess the difference in the prevalence of epicondylitis, rotator cuff syndrome, and low back pain among immigrant Latino poultry workers at plants of three different employers. Data were collected from a cross-sectional study among 286 poultry processing workers. Community-based sampling was used to recruit participants in western North Carolina. Rotator cuff syndrome (26.7%) and low back pain (27.9%) were more prevalent among employees of one specific employer. Multivariate analysis showed significant associations of low back pain and rotator cuff syndrome with age, task performed in the processing line, and employer. Employer is a major predictor of musculoskeletal disorders and pain. Line speed and work pace may account for these differences and provide an opportunity for regulation and intervention to protect the health of workers.

Shoulder muscle fatigue development in young and older female adults during a repetitive manual task

Age may modify the association between occupational physical demand and muscle loading, and ultimately increase the risk of musculoskeletal disorders. The goal of this study was to investigate age-related differences in shoulder muscle fatigue development during a repetitive manual task. Twenty participants in two age groups completed an 80-minute simulated low-intensity assembly task. Electromyographic (EMG) manifestation of muscle fatigue was observed in the upper trapezius, deltoid and infraspinatus muscles in both age groups, and coincided with an increase in the subjective ratings of perceived exertions. Compared with the younger group, older group showed a more monotonic decrease in EMG power frequency in the upper trapezius and deltoid muscles. However, the age-related difference in EMG amplitude was less consistent. Relative rest time of the upper trapezius muscle in the older group was less than the young group throughout the task. The observed patterns of EMG measures suggest that older participants may have disadvantages in fatigue resistance in the upper trapezius and posterior deltoid muscles during the simulated repetitive manual task.

Does the threshold for reporting musculoskeletal pain or the probability of attributing work-relatedness vary by socioeconomic position or sex?

OBJECTIVE

To examine the effect of sex and socioeconomic position (SEP) on individuals' perceptions of pain and its work-relatedness.

METHODS

We compared self-reported pain in neck-shoulder or arm with clinical diagnoses and workers' judgments of work-relatedness with physicians' assessments based on specific criteria, between sexes and high- and low-SEP participants in the Oslo Health Study (n = 217).

RESULTS

Clinical diagnoses were more frequent in low-SEP subjects than high-SEP subjects with pain and generally higher in women than in men. Pain attributed to work was more frequently assessed as work-related by the physicians in low-SEP subjects than high-SEP subjects and in men than in women of low SEP.

CONCLUSIONS

The threshold for reporting pain seemed higher in low-SEP subjects and among women. Physicians were more likely to agree with low-SEP workers about work-relatedness.

Impacts of differences in epidemiological case definitions on prevalence for upper-extremity musculoskeletal disorders

OBJECTIVE

The aim of this study was to systematically evaluate prevalence based on variations in case definitions used for epidemiological studies of musculoskeletal disorders (MSDs).

BACKGROUND

Prior studies of MSDs have mostly relied on a single case definition based on questionnaires.

METHOD

In a multicenter prospective cohort study, we systematically collected data to evaluate impacts of differences in case definitions of MSDs on prevalence of three common musculoskeletal disorders: (a) shoulder tendinosis, (b) lateral epicondylalgia, and (c) carpal tunnel syndrome. Production workers were from 21 employment settings in three diverse U.S. states and performed widely varying work. All workers completed laptop-administered structured interviews, two standardized physical examinations, and nerve conduction studies (NCS). Case definitions included symptoms only, and symptoms plus physical examinations and/or NCS.

RESULTS

A total of 1,227 subjects had complete health data at baseline. The prevalence for shoulder tendinosis is 23.0% if only glenohumeral pain is used for a case definition, compared with 8.0% if a combination of pain plus a positive supraspinatus test is used. The prevalence for lateral epicondylalgia varied on the basis of lateral elbow pain (12.0%), pain plus tenderness on palpation (9.9%), or pain plus tenderness on palpation plus resisted wrist or middle finger extension (3.5%). Carpal tunnel syndrome prevalence varied on the basis of tingling or numbness in a median nerve-served digit (29.9%) or tingling or numbness plus NCS abnormalities consistent with carpal tunnel syndrome (9.0%).

CONCLUSION

Variations in epidemiological case definitions have major impacts on prevalence of common MSDs. Wide-ranging differences in prevalence may have impacts on purported risk factors that need to be determined.

Self-reported neck symptoms and use of personal computers, laptops and cell phones among Finns aged 18-65

The purpose of this study was to investigate the possible relation between self-reported neck symptoms (aches, pain or numbness) and use of computers/cell phones. The study was carried out as a cross-sectional study by posting a questionnaire to 15,000 working-age persons, and 15.1% of all respondents (6121) reported that they very often experienced physical symptoms in the neck. The results showed that they also had many other symptoms very often, and 49% used a computer daily at work and 83.9% used cell phones. We compared physical/mental symptoms of persons with symptoms in the neck quite often or more, with others. We found significant differences in the physical/mental symptoms and use of cell phones and computers. The results suggest taking into account in the future that those persons' symptoms in the neck can be associated with use of cell phones or computers.

PRACTITIONER SUMMARY

We investigated the possible relation between neck symptoms and use of computers/cell phones. We found that persons, who very often had symptoms in the neck, had also other symptoms very often (e.g. exhaustion at work). Their use of information and communication technology (e.g. computers) can associate with their symptoms.

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.

Prevalence of epicondylitis, rotator cuff syndrome, and low back pain in Latino poultry workers and manual laborers

BACKGROUND

The goal of this study is to improve understanding of immigrant Latino manual workers' occupational health, focusing on upper body musculoskeletal injury.

METHODS

Physical exams were conducted with a representative sample of 516 Latino poultry workers and manual laborers in western North Carolina; outcome measures were prevalence of epicondylitis, rotator cuff syndrome, and low back pain.

RESULTS

Low back pain (n = 89; 17.2%) and rotator cuff syndrome (n = 76; 14.7%) indicated by physical exam was common. Epicondylitis was less common, but still frequent (n = 30; 5.8%). Prevalence of each outcome did not differ between poultry processing workers and other manual workers. Workers >40 years old had greater incidence of rotator cuff syndrome and epicondylitis.

CONCLUSIONS

Epicondylitis, rotator cuff syndrome, and low back pain are common in immigrant Latino workers, and may negatively impact long-term health and contribute to occupational health disparities.

Rationalisation in public dental care--impact on clinical work tasks and mechanical exposure for dentists--a prospective study

Swedish dentistry has been exposed to frequent rationalisation initiatives during the last half century. Previous research has shown that rationalisation often results in increased risk of developing work-related musculoskeletal disorders, thus reducing sustainability in the production system. In this prospective study, we assessed mechanical exposures among Swedish dentists in relation to specific rationalisations of clinical dental work during a six-year period. Body postures and movements of 12 dentists were assessed by inclinometry synchronised to video recordings of their work. No rationalisation effects could be shown in terms of a reduction in non-value-adding work ('waste'), and at job level, no major differences in mechanical exposure could be shown between baseline and follow-up.

CONCLUSION

The present rationalisation measures in dentistry do not seem to result in rationalisation at job level, but may potentially be more successful at the overall dental system level.

PRACTITIONER SUMMARY

In contrast to many previous investigations of the mechanical exposure implications of rationalisation, the present rationalisation measures did not increase the level of risk for dentists. It is highlighted that all occupations involved in the production system should be investigated to assess production system sustainability.

Motor variability in occupational health and performance

Several recent reviews have reported that 'repetitive movements' constitute a risk factor for occupational musculoskeletal disorders in the neck, shoulder and arm regions. More variation in biomechanical exposure is often suggested as an effective intervention in such settings. Since increasing variation using extrinsic methods like job rotation may not always be possible in an industrial context, the intrinsic variability of the motor system may offer an alternative opportunity to increase variation. Motor variability refers to the natural variation in postures, movements and muscle activity observed to different extents in all tasks. The current review discusses research appearing in motor control, sports sciences and occupational biomechanics literature to answer whether motor variability is important to consider in an occupational context, and if yes, whether it can be manipulated by training the worker or changing the working conditions so as to increase biomechanical variation without jeopardizing production. The review concludes that motor variability is, indeed, a relevant issue in occupational health and performance and suggests a number of key issues for further research.

Rationalization in meat cutting - consequences on physical workload

Meat cutting is associated with several ergonomic risk factors and a high risk of musculoskeletal disorders. The development of new production systems points to an increased degree of mechanization; instead of subdividing split carcasses of pigs with a knife, the halves are trisected by an electrical saw into 'sixth-parts', resulting in shorter work cycles for the workers. Recently, machine-directed line-production systems have been implemented. This study evaluates differences in the physical workload between the production systems. The postures and movements (inclinometry and goniometry) and muscular load (electromyography) of workers in the split-carcass- (five subjects), sixth-part- (ten) and line-production systems (five) were recorded. Most measures showed a statistically significant trend of declining physical exposure with increasing degrees of mechanization. For example, movement velocities of the upper arm were higher in the split-carcass system (50th percentile: mean 209°/s) than in the sixth-part (103°/s) and line production (81°/s). However, the latter two were not statistically significantly different. A novel method for quantifying posture variation, based on inclinometry, showed that the split-carcass system implied the highest variation of the upper arm postures "within-minute" (i.e., a high range of motion each minute), but the lowest "between-minute" (i.e., a low variation during the course of the workday). In conclusion, the physical workload in the line-production system was significantly lower than in the split-carcass one, and tended also to be lower than in the sixth-part system. However, there may be disadvantages in line production, such as machine-directed work pace and shorter work cycles.

Influence of fear-avoidance beliefs on functional status outcomes for people with musculoskeletal conditions of the shoulder

BACKGROUND

The influence of elevated fear-avoidance beliefs on change in functional status is unclear.

OBJECTIVE

The purpose of this study was to determine the influence of fear-avoidance on recovery of functional status during rehabilitation for people with shoulder impairments.

DESIGN

A retrospective longitudinal cohort study was conducted.

METHODS

Data were collected from 3,362 people with musculoskeletal conditions of the shoulder receiving rehabilitation. At intake and discharge, upper-extremity function was measured using the shoulder Computerized Adaptive Test. Pain intensity was measured using an 11-point numerical rating scale. Completion rate at discharge was 57% for function and 47% for pain intensity. A single-item screen was used to classify patients into groups with low versus elevated fear-avoidance beliefs at intake. A general linear model (GLM) was used to describe how change in function is affected by fear avoidance in 8 disease categories. This study also accounted for within-clinic correlation and controlled for other important predictors of functional change in functional status, including various demographic and health-related variables. The parameters of the GLM and their standard errors were estimated with the weighted generalized estimating equations method.

RESULTS

Functional change was predicted by the interaction between fear and disease categories. On further examination of 8 disease categories using GLM adjusted for other confounders, improvement in function was greater for the low fear group than for the elevated fear group among people with muscle, tendon, and soft tissue disorders (Δ=1.37, P<.01) and those with osteopathies, chondropathies, and acquired musculoskeletal deformities (Δ=5.52, P<.02). These differences were below the minimal detectable change. Limitations Information was not available on whether therapists used information on level of fear to implement treatment plans.

CONCLUSIONS

The influence of fear-avoidance beliefs on change in functional status varies among specific shoulder impairments.

Physical workload in neck, shoulders and wrists/hands in dental hygienists during a work-day

Physical workload was recorded by electromyography, inclinometry and goniometry for twelve female dental hygienists during authentic work. Their work was, in relation to other types of work, characterised by pronounced head flexion (90th percentile 46°), high loads on the forearm extensor muscles (90th percentile 23% and 18% of maximal EMG (MVE), for the right and left sides, respectively), average loads on trapezius muscles (90th percentile 15% and 14% MVE), average arm elevation (99th percentile 83° and 72°) and average wrist flexion and velocities (50th percentiles 17° of extension and 7.3°/s, for the right side). Manual scaling and machinery (use of ultrasonic scaling and hand-pieces) showed higher loads on the trapezius muscles, regarding muscular rest, as well as the 10th and 50th percentiles, than the other tasks, and for the forearm extensor muscles, an almost complete lack of muscular rest (0.1% time), and much higher loads regarding the 10th and 50th percentiles. Further, more pronounced head flexion and lower head and upper arm velocities were found, indicating more constrained postures for the neck and shoulders for the manual scaling and machinery. Use of ultrasonic scaler reduced the 50th percentile loads on the right forearm extensor muscles, but had no effect on the fraction of muscular rest and on the 10th percentile load. These findings are consistent with the high prevalences of musculoskeletal disorders among dental hygienists.

Perceived exertion, comfort and working technique in professional computer users and associations with the incidence of neck and upper extremity symptoms

Background

The aim of this study was to investigate whether perceived exertion, perceived comfort and working technique is associated with the incidence of neck and upper extremity symptoms among professional computer users.

Methods

At baseline a self-administered questionnaire was distributed to 853 participants from 46 different work sites (382 men and 471 women) who, at baseline, had been free from neck and upper extremity symptoms during the preceding month. Work-related exposures, individual factors, and symptoms from the neck and upper extremities were assessed. Observations of working technique were performed by ergonomists using an ergonomic checklist. Incidence data were collected by means of 10 monthly questionnaires, asking for information on the occurrence of neck, shoulder and arm/hand symptoms. Perceived exertion was rated on a modified Borg RPE scale ranging from 0 (very, very light) to 14 (very, very strenuous). Perceived comfort was rated on a 9-point scale ranging from -4 (very, very poor) to +4 (very, very good) in relation to the chair, computer screen, keyboard, and computer mouse.

Results

The median follow up time was 10.3 months. The incidence of symptoms from the neck, shoulders and arm/hands were 50, 24 and 34 cases per 100 person years, respectively.

Higher perceived exertion in the neck, shoulder or arm/hands was associated with an increased risk of developing symptoms in the corresponding body region. Moreover, a dose-response relationship between the level of exertion and the risk of developing symptoms was recorded for all three regions. There was an association between low comfort and an increased risk for neck symptoms, but not for shoulder and arm/hand symptoms, although a trend towards such an association (not statistically significant) could be seen. Working technique was, in this study, not associated with the risk of developing symptoms in any of the investigated body regions.

Conclusion

There was a strong association between high perceived exertion and the development of neck, shoulder, and arm/hand symptoms. Moreover, there was an association between poor perceived comfort and neck pain. Surveillance of computer users may include perceived exertion and comfort to target individuals at risk for neck and upper extremity symptoms.

Power grip force is modulated in repeated elbow movement

The objective of this study was to quantitatively investigate the modulation of power grip force under repeated elbow movement and its relation to muscle cocontraction and potential risk of developing cumulative trauma disorders (CTD). Thirteen right-handed participants without any neuromuscular disorders were recruited. Participants were instructed to hold a digital dynamometer in the hand with three levels of grip forces (20%, 40% and 60% of the maximum grip force) and perform repeated arm movement in the sagittal plane at three speeds (slow, self-paced and fast) with the upper arm voluntarily held by side by the participant. With the increase of motion rate and target force level, the grip force fluctuation, finger flexor muscle activities, elbow muscles cocontraction and apparent stiffness were significantly increased (p < 0.01). This study suggests that the power grip coupled with fast arm movement be avoided as much as possible in the workplace.

PRACTITIONER SUMMARY

Power grip is usually accompanied with arm movement in workplaces and the increased physical demand might result in higher muscle activities and potentially higher risk of repetitive musculoskeletal injuries.

Gender analysis of musculoskeletal disorders and emotional exhaustion: interactive effects from physical and psychosocial work exposures and engagement in domestic work

The objective of this study was to assess the relationships between physical and psychosocial work exposures, engagement in domestic work and work-home imbalance in relation to symptoms of musculoskeletal disorders and emotional exhaustion in white- and blue-collar men and women. Three thousand employees from 21 companies were asked to answer a questionnaire on family structure, household and child care tasks, work exposure, work-home imbalance and symptoms of neck/shoulder disorders, low back disorders and emotional exhaustion. Women reported more musculoskeletal disorders and engagement in domestic work. Adverse at-work exposures were highest in blue-collar women. High engagement in domestic work was not separately associated with symptoms but paid work exposure factors were associated. High engagement in domestic work interacted with adverse work exposure and increased risk estimates for low back disorders and emotional exhaustion. Reported work-home imbalance was associated with neck/shoulder disorders in women and with emotional exhaustion in both women and men.

PRACTITIONER SUMMARY

The current article adds to earlier research by showing that high engagement in domestic work is not separately associated with increased symptoms, but interacts with psychosocial work exposure variables to produce emotional exhaustion in both women and men and low back disorders in women.

Interaction of occupational and personal risk factors in workforce health and safety

Most diseases, injuries, and other health conditions experienced by working people are multifactorial, especially as the workforce ages. Evidence supporting the role of work and personal risk factors in the health of working people is frequently underused in developing interventions. Achieving a longer, healthy working life requires a comprehensive preventive approach. To help develop such an approach, we evaluated the influence of both occupational and personal risk factors on workforce health. We present 32 examples illustrating 4 combinatorial models of occupational hazards and personal risk factors (genetics, age, gender, chronic disease, obesity, smoking, alcohol use, prescription drug use). Models that address occupational and personal risk factors and their interactions can improve our understanding of health hazards and guide research and interventions.

Prevalence of musculoskeletal disorders and job exposure in Taiwan oyster shuckers

BACKGROUND

Oyster shucking is characterized by long hours of static work, awkward working posture, and highly repetitive hand/wrist motion. The objectives of this study were to investigate the prevalence of musculoskeletal discomfort and kyphosis in oyster shuckers in Taiwan as well as the biomechanical features of oyster shucking.

METHODS

The Chinese version of the Standardized Nordic Musculoskeletal Questionnaire was successfully collected from 234 oyster shuckers. The characteristics of workstation, hand/wrist motion angles, and muscular exertion in shucking oysters were recorded. Measurements to identify kyphosis were also taken from the subjects and a control group.

RESULTS

Among the participated oyster shuckers, low back (75.2%), hand/wrist (60.3%), shoulder (44.0%), and elbow (27.8%) discomfort were reported most frequently. The prevalence of low back discomfort in oyster shuckers was higher than various groups of workers who need long hours of seated position. Those who worked on tables had fewer musculoskeletal complaints in shoulder and elbow (P < 0.05) than those not. Additionally, oyster shuckers were more prone to kyphosis than the general population (P < 0.001).

CONCLUSIONS

Oyster shuckers are observed to have high prevalence of musculoskeletal discomfort and kyphosis. Introduction of ergonomic design to oyster shucking workshops is strongly suggested.

Mechanical exposure among general practice dentists in Sweden and possible implications of rationalisation

The present study investigates the dental work in terms of time distribution and mechanical exposure in value-adding work (VAW) and non-VAW. Further rationalisation of dental work would typically involve an increase in the proportion of VAW. Information on mechanical exposure within the classes of VAW and non-VAW may be used to predict possible implications of rationalisation. Sixteen dentists were investigated. Using a data logger, postures and movements were continuously recorded for each subject during the 4 h of work, which included the 45 min of video recording. Time distribution and mechanical exposure for the six different work activities identified were evaluated from the video recordings, using a loss analysis technique. VAW, which comprised 54% of the total working time, generally implied significantly more constrained mechanical exposures as compared with non-VAW. The results suggest that future rationalisation of dental work, involving a reduction of non-VAW, may increase the risk of developing musculoskeletal disorders. Statement of Relevance: The present study illustrates the potential effects of rationalisation on biomechanical exposures for dentists. The results highlight the significance of integrating ergonomic issues into the rationalisation process in dentistry in addition to ordinary workstation and tool design improvements performed by ergonomists.

Carpal tunnel syndrome and its relationship to occupation: a meta-analysis

OBJECTIVE

To examine the association between work place exposure and CTS by meta-analysis, including analyses with respect to exposure to hand force, repetition, vibration and wrist posture.

METHODS

All relevant peer-reviewed articles published between January 1980 and December 2009 were identified by a systematic search using the MEDLINE, CINAHL and PubMed databases. Papers were critiqued independently by two researchers and the relevant exposure information was extracted. Using the raw data of exposed and unexposed cases, a cumulative effect of specific exposure risks were calculated for hand force, repetition, a combination of force and repetition, vibration and wrist posture using the statistical program, Stata version 11 (StataCorp, College Station, TX, USA). Heterogeneity, meta-regression, publication bias and subgroup sensitivity analyses were performed.

RESULTS

Thirty-seven studies from English-language literature met the inclusion criteria. Using National Institute for Occupational Health and Safety criteria for case definition, a significant positive association between CTS and hand force, repetition, use of vibratory tools and wrist posture was observed with approximate doubling of risk for all exposures. Significant heterogeneity among studies was observed for most exposures and metaregression analyses identified CTS case definition, study design, country and risk of bias score to be the significant determinants. When a more conservative definition of CTS was employed to include nerve conduction abnormality with symptoms and/or signs, risk factors significantly associated with an increased risk of CTS among exposed workers were: vibration [odds ratio (OR) 5.40; 95% CI 3.14, 9.31], hand force (OR 4.23; 95% CI 1.53, 11.68) and repetition (OR 2.26; 95% CI 1.73, 2.94). There was a non-significant trend for the association between CTS and combined exposure to both force and repetition (OR 1.85; 95% CI 0.99, 3.45) and wrist posture (OR 4.73; 95% CI 0.42, 53.32).

CONCLUSION

Occupational exposure to excess vibration, increased hand force and repetition increase the risk of developing CTS. Workplace strategies to avoid overexposure to these risk factors should be implemented.