Pathomechanisms of work-related musculoskeletal disorders: conceptual issues

Work-related musculoskeletal disorders (WRMSDs) by definition are a subset of musculoskeletal disorders (MSDs) that arise out of occupational exposures. While traditional exposure assessment techniques have proved to be successful in identifying ergonomic exposures that are epidemiologically linked to these disorders, some are troubled by the lack of one-to-one correspondence between specific occupational exposure profiles and specific MSDs. In the absence of more sophisticated hypotheses that might explain the occurrence of WRMSDs in a variety of exposure patterns, the aetiologic relationships may (again) be called into question. Another unanswered question is whether specific types of WRMSDs have qualitatively different exposure-response relationships. A clearer understanding of the underlying pathomechanisms associated with specific WRMSDs could help future researchers better determine how and when various occupational exposure profiles become pathogenic. Such knowledge could also be used to design exposure assessment tools to capture exposure information more relevant to the risk of WRMSDs. The main goals of this paper are to summarize several recently described pathomechanisms, most of which have been discussed primarily in clinical and experimental literature that might not be widely read by occupational health scientists. Suggestions are made as to how future research could evaluate whether these phenomena are relevant to the effects of physical exposures and the underlying disease processes of common WRMSDs.     

Pathomechanisms of work-related musculoskeletal disorders: conceptual issues

Work-related musculoskeletal disorders (WRMSDs) by definition are a subset of musculoskeletal disorders (MSDs) that arise out of occupational exposures. While traditional exposure assessment techniques have proved to be successful in identifying ergonomic exposures that are epidemiologically linked to these disorders, some are troubled by the lack of one-to-one correspondence between specific occupational exposure profiles and specific MSDs. In the absence of more sophisticated hypotheses that might explain the occurrence of WRMSDs in a variety of exposure patterns, the aetiologic relationships may (again) be called into question. Another unanswered question is whether specific types of WRMSDs have qualitatively different exposure-response relationships. A clearer understanding of the underlying pathomechanisms associated with specific WRMSDs could help future researchers better determine how and when various occupational exposure profiles become pathogenic. Such knowledge could also be used to design exposure assessment tools to capture exposure information more relevant to the risk of WRMSDs. The main goals of this paper are to summarize several recently described pathomechanisms, most of which have been discussed primarily in clinical and experimental literature that might not be widely read by occupational health scientists. Suggestions are made as to how future research could evaluate whether these phenomena are relevant to the effects of physical exposures and the underlying disease processes of common WRMSDs.     

The Strain Index (SI) and Threshold Limit Value (TLV) for Hand Activity Level (HAL): risk of carpal tunnel syndrome (CTS) in a prospective cohort

A cohort of 536 workers was enrolled from 10 diverse manufacturing facilities and was followed monthly for six years. Job physical exposures were individually measured. Worker demographics, medical history, psychosocial factors, current musculoskeletal disorders (MSDs) and nerve conduction studies (NCS) were obtained. Point and lifetime prevalence of carpal tunnel syndrome (CTS) at baseline (symptoms + abnormal NCS) were 10.3% and 19.8%. During follow-up, there were 35 new CTS cases (left, right or both hands). Factors predicting development of CTS included: job physical exposure (American conference of governmental industrial hygienists Threshold Limit Value (ACGIH TLV) for Hand Activity Level (HAL) and the Strain Index (SI)), age, BMI, other MSDs, inflammatory arthritis, gardening outside of work and feelings of depression. In the adjusted models, the TLV for HAL and the SI were both significant per unit increase in exposure with hazard ratios (HR) increasing up to a maximum of 5.4 (p = 0.05) and 5.3 (p = 0.03), respectively; however, similar to other reports, both suggested lower risk at higher exposures. Data suggest that the TLV for HAL and the SI are useful metrics for estimating exposure to biomechanical stressors. PRACTITIONER SUMMARY: This study was conducted to determine how well the TLV for HAL and the SI predict risk of CTS using a prospective cohort design with survival analysis. Both the TLV for HAL and the SI were found to predict risk of CTS when adjusted for relevant covariates.     

Associations of ergonomic and psychosocial work hazards with musculoskeletal disorders of specific body parts: A study of general employees in Taiwan

Background and aimsMusculoskeletal disorders (MSDs) are major occupational health concerns. This study examined the associations of ergonomic and psychosocial work hazards with the risks of MSDs of specific body parts and their distribution across a wide range of occupational groups.MethodsStudy participants comprised 8,937 male and 7,052 female employees aged 20–65 years from a nationwide survey in 2016. A self-report questionnaire was administered to obtain information regarding demographic characteristics, work conditions, ergonomic and psychosocial work hazards, and MSDs of different body parts in 12 months. Multivariate logistic regression models were used to estimate prevalence ratios of MSDs in relation to ergonomic and psychosocial work hazards.ResultsIn professionals and skilled workers, MSDs of the neck and shoulders were more prevalent, whereas in manual workers, MSDs of the hands, wrists, and lower back were more prevalent. Psychosocial work hazards, including high psychological demand and low workplace justice, were major work-related risk factors for shoulder and neck disorders, whereas ergonomic hazards were major work-related risk factors for lower back and wrist or hand disorders.ConclusionDifferent workplace hazards contribute to the risks of different MSDs. To prevent the development of MSDs, occupational health professionals should evaluate both ergonomic and psychosocial work hazards and develop health prevention programs tailored to the risk profiles of working populations.     

Medium- and long-term reproducibility of self-reported exposure to physical ergonomics factors at work

INTRODUCTION: The literature is sparse on reproducibility of self-reported exposure to physical ergonomics risk factors for musculoskeletal disorders (MSDs). Aims of this study were to evaluate, in a cohort of workers interviewed up to three times: 1-year test-retest reliability; and 5- and 6-year recall of physical exposures. We also examined whether reproducibility was influenced by the presence of UE MSD or by technological changes introduced between the last two surveys. METHODS: A cohort of automobile manufacturing employees was interviewed at baseline, one and six years later about work history, physical and psychosocial exposures at work, upper limb symptoms, injury and medical history, and demographics. Agreement between interviews was evaluated by intraclass correlation and Spearman coefficients. Differences in exposure between 1- and 6-year follow-up were analyzed by Wilcoxon matched-pairs signed-ranks test. RESULTS: Large and significant decreases in work pace and physical effort were observed from baseline, although an upper extremity composite index was quite stable in the total population. One-year test-retest reliability was fair to good for the composite exposure index (ICC=0.58), whole-body vibration, handling parts, and tool use, but poor for the other variables considered. Long-term reproducibility, from baseline or 1-year follow-up to 6-year follow-up, was poor for the composite index and almost all single items. UE MSD case status influenced 1-year test-retest reliability, with subjects who changed case status from baseline displaying higher reliability, but not reproducibility of recalled exposures. A strong regression to the mean effect was observed on exposures reported at follow-up surveys. CONCLUSIONS: Recalled ergonomics exposures could be employed in retrospective cohort studies as a somewhat reliable and unbiased estimate of the self-reported exposures that would have been obtained up to one year earlier, but not over a longer period (5-6 years). These longer-term results may have been limited by difficulty in matching jobs between interviews; also the regression to the mean effect likely contributed to reduce agreement. Changes in production technology and work organization produced a decrease in physical workload intensity and job pace, but did not have a substantial impact on an exposure index for the upper limb.     

Psychosocial risk exposures and musculoskeletal disorders across working‐age males and females

In 2008, The European Agency for Safety and Health at Work (EU‐OSHA) reported that musculoskeletal disorders (MSDs) were the most common work‐related health problem in Europe. Females are considered more susceptible to MSDs than are males, and older workers are more vulnerable than are younger workers. Factors specific to the job, work organization, and individual have been implicated as potential risk factors, with current interest focusing on psychosocial risk factors and the pathology of disorders. Although there is some disagreement in the literature, there is growing support that, after controlling for exposure, females have a predisposition to MSDs. More is known of the role of psychosocial risks in MSD etiology, but it is unclear if there are differences in exposures across gender and age and if this has a resultant effect on injury rates. The purpose of this study was to investigate the prevalence of MSDs and trends with psychosocial risks, across age and gender. The study group consisted of 200 female and 132 male employees from varied occupations within Ireland, ranging from age 18–66 years. The most prevalent symptoms of MSDs were for the lower back, shoulder, and neck regions. Age and gender differences in prevalence were evident for these regions. There was a general trend for increasing prevalence with age. For the psychosocial risks, significant differences in job content exposures were observed across age groups for males (p < 0.05) and females (p < 0.0005). There were also differences in scores across the age groups for mental health (p < 0.0005) and insecurity at work (p < 0.0005) for the females. The conclusions are that there were not sufficiently strong differences in exposures to relevant psychosocial risks both between genders and across age for a resultant effect on MSDs. © 2010 Wiley Periodicals, Inc.     

Types of manual materials handling (MMH) and occupational incidents and musculoskeletal disorders (MSDs) in motor vehicle parts manufacturing (MVPM) industry

The motor vehicle parts manufacturing (MVPM) works include various types of manual materials handling (MMH). This study analyzes occupational incidents and musculoskeletal disorders (MSDs) caused by MMH in the MVPM industry. Also, this study conducted a risk assessment for predicting the possibility and severity of the injuries and MSDs. This study examined 236 injured persons registered for occupational incidents and MSDs caused by MMH tasks. Of the 236 injuries, 124 (52.5%) were caused by lifting/lowering, followed by 92 (39.0%) pushing/pulling and 20 (8.5%) carrying. MSDs were the highest at 36.9%, followed by struck by (22.9%), caught in (19.5%), and slip/fall (9.7%) incidents. In the case of incidents, the percentage caused by pushing/pulling was the highest at 55.7%, followed by lifting/lowering (35.6%) and carrying (8.7%). However, in the case of MSDs, the percentage caused by lifting/lowering was the highest at 81.6%, followed by pushing/pulling (10.3%) and carrying (8.0%). However, the rate of severe injured with over 180 work-loss days was higher in carrying works, women, or older workers over 50 years. The highest prevalence of MSDs was low back (63.2%), followed by shoulders (17.2%), and arm/hand regions (16.1%). In risk assessment according to the work process, ‘struck by incidents during pushing/pulling carts in the logistics process’ is the most possible and the highest average of work-loss days.Relevance to industryThis study presents the overview of actual nationwide compensation records occurred during MMH tasks in the MVPM industry. Also, this study shows the outlines of occupational incidents and MSDs, and the most possible and severe incident according to the types of MMH and work process.     

Work routinization and implications for ergonomic exposure assessment

Jobs in many modern settings, including manufacturing, service, agriculture and construction, are variable in their content and timing. This prompts the need for exposure assessment methods that do not assume regular work cycles. A scheme is presented for classifying levels of routinization to inform development of an appropriate exposure assessment strategy for a given occupational setting. Five levels of routinization have been defined based on the tasks of which the job is composed: 1) a single scheduled task with a regular work cycle; 2) multiple cyclical tasks; 3) a mix of cyclical and non-cyclical tasks; 4) one non-cyclical task; 5) multiple non-cyclical tasks. This classification, based primarily on job observation, is illustrated through data from a study of automobile manufacturing workers (n = 1200), from which self-assessed exposures to physical and psychosocial stressors were also obtained. In this cohort, decision latitude was greater with higher routinization level (p < 0.0001), and the least routinized jobs showed the lowest self-reported exposure to physical ergonomic stressors. The job analysis checklist developed for non-routinized jobs is presented, and limitations of the task analysis method utilized in the study are discussed. A work sampling approach to job analysis is recommended as the most efficient way to obtain a comparable unbiased exposure estimate across all routinization levels.     

Reaction load exposure from handheld powered tightening tools: A scoping review

Assembly workers using handheld powered tightening tools are repetitively subjected to reaction loads resulting from the tool handle. Despite the vast amount of research, tool manufacturers and OSH practitioners still lack well-grounded recommendations and benchmarks for ergonomics evaluations of reaction loads. This review provides an overview of research investigating reaction loads and operator physical demand, and identifies gaps in current means of evaluating reaction load exposure from tightening tools. A scoping review was conducted, scanning for quantifications of reaction loads as well as reported indications of MSD risks following tightening tool use. Suggested maximum exposures for reaction loads were further identified. The most commonly investigated quantities among the 40 publications included, were peak reaction force/torque (70%) and handle displacement (70%), followed by impulse (23%). Pneumatic tools were studied at greater extent (65%) than electric tools (30%). Three studies presented a relationship between reaction load exposure and physiological changes, i.e. edema, tissue oxygenation and blood volume changes, indicating an elevated risk of developing MSDs. Four publications proposed values for maximum reaction load exposure, expressed as either reaction torque, handle displacement, or tightening torque. To conclude, strategies for developing recommendations for reaction load exposure are suggested. Less investigated reaction parameters, e.g. impulse, can carry additional relevant information regarding exposure. Exposure values should be expressed as physical quantities of the reaction load rather than tightening torque. Recommendations are further needed for various tool handle-configurations, emphasizing the increasingly used electric tools. Such recommendations can eventually contribute to reducing MSDs resulting from tightening tool use.     

Further studies of shoulder and neck pain and exposures in customer service work with low biomechanical demands

The aim of the study was to establish insight into work exposures that cause shoulder and neck pain among occupational groups that have low biomechanical exposure and experience work stress from client/customer contact, among other exposures. Four occupational groups were studied, in health care (n = 20), retail (n = 22), banking (n = 26), and university secretaries (n = 26), a total of 94 volunteers. Thirty-nine were classified as pain-afflicted in the shoulder and neck, while 55 were pain-free. The subjects' perceptions of biomechanical and psychosocial exposures were established by use of quantitative questionnaires and by explorative interviews with open-ended questions, covering the same themes. Heart rate and trapezius EMG were recorded over a full workday and the following leisure period. Trapezius median and static activity during work were 3.3% and 0.3% EMG(max), only marginally higher than trapezius activity in the leisure period (2.7% and 0.2% EMG(max)). The quantitative questionnaire did not identify any variable that correlated with shoulder and neck pain except perceived general tension. The interviews established that the interaction with clients or customers was an important source of work stress. Such stress appeared to be a complex entity not easily characterized by established psychosocial questionnaires. The physiological variables were at most weakly elevated in periods with high stress as compared to periods with low stress. The authors caution against relying on standardized quantitative questionnaires and/or physiological recordings to characterize work stress in occupations with emotional stress through client/customer service work.     

Shoulder and neck complaints in customer relations: individual risk factors and perceived exposures at work

Perceived psychosocial and biomechanical exposures, individual factors and pain in the shoulder and neck were recorded in two groups of female service workers (healthcare and shopping centre workers). The jobs investigated were characterized by 'much' direct human relations, 'little' sitting and 'much' standing, and were light work by physiological or biomechanical criteria but potentially psychosocially demanding. A screening survey (n = 400 females) was the basis for the selected sample (n = 66 females), which was the object of the main investigation of this study. Reliability of the questionnaires was tested in a separate group of female healthcare workers (n = 29). Heart rate recordings through the work day estimated workload. There was a high prevalence of shoulder and neck pain (> 50%) for both work groups. In the two populations it proved difficult to explain shoulder and neck pain by reported physical and psychosocial exposures or individual factors, except by the variable 'perceived general tension', which clearly differentiated workers with and without pain. The findings in this study indicated, first, that perceived general tension might be an independent risk factor for muscle pain and, second, that this might be related to personality factors. However, this putative relationship must be verified in a longitudinal study. As no variable describing exposures in the working environment was associated with shoulder and neck pain, the question is posed whether such complaints can be considered work-related. Alternatively, the variables used to describe mechanical and psychosocial exposures in this study may have low specificity in characterizing work-related risk factors for service workers with customer relations.     

Musculoskeletal disorder prevalence and psychosocial risk exposures by age and gender in a cohort of office based employees in two academic institutions

This study presents data on self-reported prevalence of Musculo-Skeletal Disorder (MSD) symptoms and psychosocial risk exposures by age and gender among a group of office based University workers who use their computers for at least 25% of their workday. Employees in two academic organisations received an invitation to participate in an on-line questionnaire. A total of n = 852 office workers participated in this study; yet respondents who were employed for greater than 12 months were only included in the study cohort. Furthermore, participants were only considered for further analysis if they spent 50% or more of their workday in their office, and of this time at least 50% was spent on computer work (n = 569). The study indicates that self-reported symptoms of MSDs for these workers were highest in the neck, shoulder and lower back. Neck, shoulder and back MSDs were higher for females than males, yet age differences within genders were not evident for these symptoms. For neck disorders, symptomatic individuals reported significantly higher levels of office work (p < 0.05) and PC usage (p < 0.005), and significantly lower levels of job content (p < 0.01), job demands (p < 0.05), and work environment (p < 0.05) compared to asymptomatic participants. For the shoulder, symptomatic individuals exposure levels were significantly higher for office work (p < 0.05) and PC usage (p < 0.05) and significantly lower for job content (p < 0.05) compared to asymptomatic individuals. There was evidence of important differences in the psychosocial exposures between age and genders, but associations between these differences and MSD symptoms were not present.Relevance to industryThis study presents prevalence data on age and gender differences in self-reported symptoms of MSDs and psychosocial risk exposures in a group of sedentary workers.     

Musculoskeletal disorders in hospital nurses: a comparison between two hospitals

Nursing staff members of a urban general hospital (GH) and a small oncological department (OD) were surveyed to determine the prevalence of occupational related musculoskeletal disorders (MSDs), the specific disabilities, accidents at work, and working time lost. All subjects had a medical examination to evaluate osteoarthicular disease and selected cases were invited to X-ray examinations. The purpose of this study was to compare MSDs in the two groups of nurses working in two hospitals with different work organization in the same geographical area, Pordenone in Italy. In the previous year 48% GH and 33% OD nurses reported back pain due to work, 29·4 and 16·1% respectively have had X-ray or orthopaedic examinations, 19·2% and 9·1% had been away from work because of back pain. All these differences are statistically significant. The analysis of musculoskeletal pain sites and working tasks in the two hospital workers shows no differences in distribution. Great difference exists when analysing the numbers of patients assisted by a nurse: 0·57 and 1·27 nurse/patients respectively in GH and OD. Our data indicate a high overall frequency of occupational back pain, similar to other studies in Europe. The comparison between the two hospitals suggests factors associated with the disorder: work tasks and particularly nurses/patients ratio are more important factors than age and length of exposure. Different work distribution, shift organization, a better ratio between nurses and patients, an improvement of equipment provision, and specific nurse-training with application of ergonomic methods could improve work efficiency radically and decrease injury rates.     

Hybrid procedure to determine optimal workforce without noise hazard exposure

Hearing loss is a major occupational health problem among industrial workers. Repetitive exposure to loud noise increases the risk of hearing loss. An administrative noise control such as job rotation can help to reduce workers’ daily noise exposures. In a case where noise levels are excessively high, it is often necessary to assign additional workers to the current workforce to alleviate daily noise exposures that individual workers receive. This paper presents four solution algorithms (three approximations and one exact) to determine a minimum number of workers and their work assignments to attend noisy workstations without noise hazard exposure (that is, daily noise exposure does not exceed 90 dBA). Then, a hybrid procedure which utilizes the four algorithms successively is proposed to improve the solution procedure. Based on a computational experiment on 300 test problems, it is found that the hybrid procedure outperforms all four algorithms (when utilized separately) and is able to find an optimal solution for 88% of the test problems.     

Hybrid procedure to determine optimal workforce without noise hazard exposure

Hearing loss is a major occupational health problem among industrial workers. Repetitive exposure to loud noise increases the risk of hearing loss. An administrative noise control such as job rotation can help to reduce workers’ daily noise exposures. In a case where noise levels are excessively high, it is often necessary to assign additional workers to the current workforce to alleviate daily noise exposures that individual workers receive. This paper presents four solution algorithms (three approximations and one exact) to determine a minimum number of workers and their work assignments to attend noisy workstations without noise hazard exposure (that is, daily noise exposure does not exceed 90 dBA). Then, a hybrid procedure which utilizes the four algorithms successively is proposed to improve the solution procedure. Based on a computational experiment on 300 test problems, it is found that the hybrid procedure outperforms all four algorithms (when utilized separately) and is able to find an optimal solution for 88% of the test problems.     

Injury risk associated with physical demands and school environment characteristics among a cohort of custodial workers

Few epidemiological studies have investigated the relationship between work exposures and injury risk among custodians. The relationship between injury risk and occupational physical demands (e.g. pushing/pulling, lifting) and school environment characteristics (e.g. school type, season) was investigated among a cohort of 581 school custodians over a 4-year period. In the final Poisson regression models, the risk of injury was associated with time spent in pushing/pulling tasks in a dose-response manner increasing to a five-fold risk among the highest quartile of exposure (risk ratio?=?5.15, 95% CI 1.00, 26.5). Injury risk was also associated with working during the school year compared to the summer, working in a school with grass vs. gravel grounds and working in a school with detached classrooms. Results help to target interventions such as alternative methods for floor cleaning to reduce the pushing/pulling demands of custodial work and to support decisions for alternatives to detached classrooms and grass surfaces. Statement of Relevance: This study examines ergonomic factors (physical demand exposures, school environment characteristics) associated with injury risk among custodial school workers. The findings help schools to target interventions to reduce the physical demands associated with injuries and to design school environments to reduce exposures.     

The ability of non-computer tasks to increase biomechanical exposure variability in computer-intensive office work

Postures and muscle activity in the upper body were recorded from 50 academics office workers during 2 hours of normal work, categorised by observation into computer work (CW) and three non-computer (NC) tasks (NC seated work, NC standing/walking work and breaks). NC tasks differed significantly in exposures from CW, with standing/walking NC tasks representing the largest contrasts for most of the exposure variables. For the majority of workers, exposure variability was larger in their present job than in CW alone, as measured by the job variance ratio (JVR), i.e. the ratio between min–min variabilities in the job and in CW. Calculations of JVRs for simulated jobs containing different proportions of CW showed that variability could, indeed, be increased by redistributing available tasks, but that substantial increases could only be achieved by introducing more vigorous tasks in the job, in casu illustrated by cleaning.     

Musculoskeletal disorders in labor-intensive agriculture

This paper gives an overview of the extent of musculoskeletal disorders (MSDs) in agriculture, and a historical perspective on how ergonomics has been used to reduce the health effects of labor-intensive agriculture. A summary of exposure to MSD physical risk factors within various classes of crops, along with various administrative and engineering controls for abating MSDs in agriculture is given. These controls range from programmed rest breaks to mechanized or partially-mechanized operations. Worker-based approaches such as prone carts and platforms, and load transfer devices hold promise in combating the prevalent stooped work in agriculture. Including the worker as an integral contributor to all aspects of developing and implementing an intervention, and considering the psychosocial and socio-cultural aspects of the work environment are crucial elements of effective interventions for reducing MSDs. Despite the advent progress in new technologies in agricultural practices, reliance on labor, especially in fresh market fruits and vegetables, will always be a major cornerstone of agriculture for at least the foreseen future. It is encouraging to see the increased interest among health and safety professionals, epidemiologists, engineers, social scientists, and ergonomists throughout the world who are committed to the plight of reducing MSDs and other health problems among agricultural workers.     

Quantitative and qualitative assessment of musculoskeletal disorders and socioeconomic issues of workers of brick industry in Pakistan

Brick industry, in Pakistan, is prominent and provides job to 3.1 million people only in one province. The industry hires different percentage of workers for different stages of brick formation and these stages trigger musculoskeletal disorders (MSDs) in workers. This study identifies relation between 5 work stages and MSDs in 9 body parts and also finds socioeconomic sufferings inflicted by the industry and removal of research gap at national level. We conducted both qualitative and quantitative research. 105 men and 45 women from 15 brick kilns were selected as subject. Rapid Upper Limb Assessment (RULA) and Rapid Entire Body Assessment (REBA) sheets, Standard Nordic MSDs Questionnaire along with general questionnaire, still photography and video recording were used to carry out the study. About 96% workers involved in mixing & molding complained tiredness at end of day. Similarly, 90% male and 83% female staff performing spreading task suffered tiredness after their duty hours. Workers engaged in different tasks reported varying levels of pain in observed body parts. Digging and carrying jobs caused significant pain in body parts including neck, upper back, shoulders, lower back and hips. Mixing and molding emerged most dangerous activities for most of the body parts and exhibited 7 score on RULA. Furthermore, mixing and molding demonstrated high to very high risk level by showing 9 and 13 higher score on REBA, respectively. The current study divulged that all observed work tasks during manufacturing and transportation of bricks are equally dangerous for pain generation in lower back. Many socioeconomic issues like residency of workers in muddy house (83%) low monthly income (<90.3 $) of 83% workers, higher tendency of alcoholism and smoking in men, lack of health facilities and higher illiteracy rate were also identified. The enhanced musculoskeletal disorders during brick making process render the brick industry unhealthy for work. This dismal picture requires an improvement in quality of life and occupational environment of workers of the industry. Well organized duty timings, modified working posture, job rotation and preliminary training perhaps manage these miseries and the output of the brick industry may increase many fold.     

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

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