An examination of shoulder kinematics and kinetics when using a commercial trunk harness while sheep shearing

Sheep shearing is a very physically demanding occupation, especially on the low back, such that many commercial harnesses have been developed to help reduce the load on the back. Such harnesses have been shown to significantly reduce peak and cumulative low back loads; however, the effect that these harnesses have on the shoulders, which are also highly involved during sheep shearing, has not been previously examined. The purpose of this study was to examine the shoulder postures and cumulative shoulder moments of 12 New Zealand sheep shearers. The use of the trunk harness reduced the percentage of time spent in shoulder flexion greater than 90 degrees and the time spent in shoulder abduction greater than 45 degrees as well as reduced the cumulative net joint flexor, abductor, and adductor shoulder moments by a minimum of 21%, 14%, and 42%, respectively. Therefore, the use of a commercial trunk harness to reduce low back injury may also help to reduce the risk of shoulder injury while sheep shearing.     

The effects of job rotation on the risk of reporting low back pain

Job rotation has been widely recommended as an administrative control to reduce the risk of developing work-related musculoskeletal disorders. However, evidence of its benefits are hard to find in the literature. The effect of job rotation on predictions for the risk of reporting low back pain was estimated using Low Back Pain Reporting (LBPR) and Time Weighted Average (TWA) approaches. Index scores calculated using the peak hand force, the peak L4/L5 shear force and the L4/L5 moment cumulated over the entire shift were used to estimate the effects of job rotation on the probability of reporting low back pain. Simulations of realistic rotations between two jobs showed that workers in low demand jobs who rotate into higher demand jobs experience a linear increase in reporting probability using the TWA approach. With the LBPR approach a step increase in reporting probability occurred because of the immediate exposure to the peak loading parameters associated with the more demanding job. With a 50-50 rotation the TWA and LBPR index scores increased by 39% and 57%, respectively. With the LBPR approach the redistribution of risk was not uniform with job rotation. The increase was greater for those who rotated into the demanding job compared to the reduction experienced by those who rotated out of the demanding job. The effects of job rotation are not easily estimated because of the complex effect that mixing jobs has on peak and cumulative tissue loading.     

The influence of skill and low back pain on trunk postures and low back loads of shearers

Shearing is a rural occupation developing considerable spinal loads and carrying a high risk of low back pain (LBP). Although the workforce has a skill structure, interaction between skill, spinal loads and LBP is unknown. We examined whether skill and LBP influenced trunk postures and loads within a sample of 80 shearers representing shear skill levels. A progression from junior to open class demonstrated a 100% increase in productivity, less time in severe flexion, more time in neutral lateral bend, and more time in axially twisted postures, with no increase in cumulative compressive and anterior shear forces. LBP prevalence increased linearly from 10% for junior through to 76% for open class shearers. Shearers with a history of LBP generated greater cumulative right medio-lateral shear forces, greater left lateral bend and left axial twist moments. Skill-based training that reduces asymmetric forces may help reduce such high prevalence levels of LBP.

Statement of Relevance: Shearing is an important and physically demanding rural occupation. It requires sustained flexed postures that generate considerable spinal loads and a high risk of LBP. This research examines how skill and a history of LBP it carries interact to influence trunk postures and spinal loads within a sample of shearers.     

Trunk postures and peak and cumulative low back kinetics during upright posture sheep shearing

Sheep shearing is the most demanding occupation in the wool harvesting industry and is known to have a high prevalence of low back pain. While use of a commercially available trunk harness reduces load on the low back, the extreme trunk flexion associated with shearing still remains. A novel, upright posture shearing technique has been designed to allow a more neutral spine posture. This study assessed this upright technique and found significant reductions in both trunk flexion and cumulative low back loading when compared to either the traditional method or the use of the trunk harness. Moments about the shoulder tended to be higher while using the upright shearing technique and further investigation of shoulder kinetics will be required to assess whether this creates injury risk to the upper extremity. Despite increased shoulder moments, the reduction in flexion and cumulative loading with the use of the upright technique has the potential to reduce risk of low back pain among shearers.     

The effects of job rotation on the risk of reporting low back pain

Job rotation has been widely recommended as an administrative control to reduce the risk of developing work-related musculoskeletal disorders. However, evidence of its benefits are hard to find in the literature. The effect of job rotation on predictions for the risk of reporting low back pain was estimated using Low Back Pain Reporting (LBPR) and Time Weighted Average (TWA) approaches. Index scores calculated using the peak hand force, the peak L4/L5 shear force and the L4/L5 moment cumulated over the entire shift were used to estimate the effects of job rotation on the probability of reporting low back pain. Simulations of realistic rotations between two jobs showed that workers in low demand jobs who rotate into higher demand jobs experience a linear increase in reporting probability using the TWA approach. With the LBPR approach a step increase in reporting probability occurred because of the immediate exposure to the peak loading parameters associated with the more demanding job. With a 50-50 rotation the TWA and LBPR index scores increased by 39% and 57%, respectively. With the LBPR approach the redistribution of risk was not uniform with job rotation. The increase was greater for those who rotated into the demanding job compared to the reduction experienced by those who rotated out of the demanding job. The effects of job rotation are not easily estimated because of the complex effect that mixing jobs has on peak and cumulative tissue loading.     

Estimating investment worthiness of an ergonomic intervention for preventing low back pain from a firm's perspective

A mathematical model was developed for estimating the net present value (NPV) of the cash flow resulting from an investment in an intervention to prevent occupational low back pain (LBP). It combines biomechanics, epidemiology, and finance to give an integrated tool for a firm to use to estimate the investment worthiness of an intervention based on a biomechanical analysis of working postures and hand loads. The model can be used by an ergonomist to estimate the investment worthiness of a proposed intervention. The analysis would begin with a biomechanical evaluation of the current job design and post-intervention job. Economic factors such as hourly labor cost, overhead, workers' compensation costs of LBP claims, and discount rate are combined with the biomechanical analysis to estimate the investment worthiness of the proposed intervention. While this model is limited to low back pain, the simulation framework could be applied to other musculoskeletal disorders. The model uses Monte Carlo simulation to compute the statistical distribution of NPV, and it uses a discrete event simulation paradigm based on four states: (1) working and no history of lost time due to LBP, (2) working and history of lost time due to LBP, (3) lost time due to LBP, and (4) leave job. Probabilities of transitions are based on an extensive review of the epidemiologic review of the low back pain literature. An example is presented.     

A prospective cohort study of neck and shoulder pain in professional drivers

In a three-year follow-up study, the occurrence of neck and shoulder pain (NSP) in terms of frequency, duration and intensity was investigated in a population of 537 male professional drivers. Over the follow-up period, the cumulative incidences for neck and shoulder pain were 31.9% and 21.4%, respectively. After adjustment for potential confounders, a measure of cumulative whole-body vibration exposure was significantly associated with all NSP outcomes. Lifting loads and work with hands above shoulder level were significantly related to shoulder outcomes, while driving with trunk bent or twisted was associated with neck pain. Limited job decision, low social support and job dissatisfaction were significant predictors of neck outcomes. Psychological distress was associated with all NSP outcomes. The findings of this cohort study suggest that NSP outcomes are of multifactorial origin in driving occupations.

Practitioner Summary: This prospective cohort study highlighted the multifactorial nature of neck and shoulder pain (NSP) outcomes in a population of professional drivers. Cumulative whole-body vibration exposure, physical load factors and adverse psychosocial environment at the workplace, as well as individual-related psychological distress, were significant predictors of the occurrence of NSP in the professional drivers.     

Continuous assessment of low back loads in long-term care nurses

Considerable effort has been spent evaluating aspects of low back injury risk in nursing yet comprehensive evaluation of all work tasks has been limited. The purpose of this study was to evaluate peak and cumulative lumbar spine loads experienced by personal support workers. A total of 20 female long-term care workers were observed and had trunk posture monitored via an inclinometer throughout their shift. When adjusted for an 8-h workday, workers experienced cumulative loads of 21.3 ± 4.6 MNs, 1.8 ± 0.6 MNs and 2.9 ± 1.4 MNs for compression, lateral and anterior shear, respectively. Patient care, unloaded standing, walking and miscellaneous tasks accounted for almost 80% of cumulative compression, while lifts and transfers accounted for less than 10%. Mechanical lift assists reduced peak loads and contributed minimally to cumulative loading. These findings suggest that both peak and cumulative spine loads should be considered when evaluating injury risk in the nursing profession.

Statement of Relevance: This study has shown that tasks other than patient transfers and lifts are important in the assessment of low back injury risk in nurses. The method developed is a relatively straightforward approach that can be used to estimate peak and cumulative spine load to provide insight to risk of injury in many occupational settings.     

Age-related biomechanical differences during asymmetric lifting

This study investigated age-related biomechanical differences during asymmetric lifting. Eleven younger and twelve older participants were instructed to lift loads of different weights to an asymmetric destination. The trunk kinematics and low back moments were examined. The results showed that older adults adopted safer lifting strategies compared with younger adults. Specifically, the peak trunk sagittal flexion angle was 32% lower and the peak trunk transverse twisting angle was 22% lower in older adults compared with those in younger adults. It was also found that the average low back moment in the deposit phase was 32% higher in older adults than that in younger adults, most probably due to the age-related increased body weight. Based on these findings and the fact of age-related decreased muscle strengths, physical exercise programs were suggested to be more effective than instructions of safe lifting strategies in LBP risk reduction during asymmetric lifting for older adults. For younger adults, safe lifting strategy instructions might be effective to reduce risks of LBP.     

The interaction between skill, postures, forces and back pain in wool handling

Wool handling is an important rural occupation where workers process 200 or more fleeces daily, separating them into various quality components. Loads and postures they experience carry substantial risk of low back pain (LBP). Although a formal skill training structure exists, interaction with loads and LBP is unknown. We examined whether skill and LBP influenced trunk postures and loads of 60 wool handlers representing 3 skill levels. LBP prevalence ranged from 20% for junior (lowest skill) to 45% for open class (highest skill) wool handlers. Open class wool handlers demonstrated increased lateral bend and more axially twisted postures, generating greater medio-lateral shear forces and lateral bend and axial twist moments. LBP was associated with open class wool handlers spending more time in severe axially twisted postures. These findings suggest that skill-based training needs to be reviewed to reduce the quantity of axially twisted posture which may help reduce the prevalence of LBP in this workforce.     

Quantifying low back peak and cumulative loads in open and senior sheep shearers in New Zealand: Examining the effects of a trunk harness

Sheep shearing requires shearers to adopt sustained flexed postures for prolonged periods of time and has been associated with an increased risk of developing low back pain (LBP). However, these postures do not generally result in acute compressive values at L4/L5 exceeding the action limit proposed by the National Institute for Occupational Safety and Health, despite the high prevalence of LBP in this occupation. Therefore, it may not be peak loading that is responsible for LBP in this occupation but instead it may be the effect of cumulative loading over the course of a workday. The primary purpose of this research was to quantify the low back cumulative load exposure in 12 sheep shearers with and without the aid of a commercial trunk harness. Results revealed a significant reduction in the magnitude of cumulative compression with the use of the trunk harness and therefore its use may potentially reduce the risk of injury. The use of the trunk harness also reduced the time spent in axially twisted postures, which have been associated with LBP. However, using the trunk harness also resulted in increased time spent in laterally bent postures, which has been associated with increased risk for pain and injury.     

Quantifying low back peak and cumulative loads in open and senior sheep shearers in New Zealand: examining the effects of a trunk harness

Sheep shearing requires shearers to adopt sustained flexed postures for prolonged periods of time and has been associated with an increased risk of developing low back pain (LBP). However, these postures do not generally result in acute compressive values at L4/L5 exceeding the action limit proposed by the National Institute for Occupational Safety and Health, despite the high prevalence of LBP in this occupation. Therefore, it may not be peak loading that is responsible for LBP in this occupation but instead it may be the effect of cumulative loading over the course of a workday. The primary purpose of this research was to quantify the low back cumulative load exposure in 12 sheep shearers with and without the aid of a commercial trunk harness. Results revealed a significant reduction in the magnitude of cumulative compression with the use of the trunk harness and therefore its use may potentially reduce the risk of injury. The use of the trunk harness also reduced the time spent in axially twisted postures, which have been associated with LBP. However, using the trunk harness also resulted in increased time spent in laterally bent postures, which has been associated with increased risk for pain and injury.     

A review of: “Catastrophic Failures”. By V. BIGNELL,G. PETERS and C. PYM. (Milton Keynes: OPEN UNIVERSITY PRESS, 1977.) [Pp.274.] £5·50.

Cumulative trauma illness currently accounts for over half of all occupational illness in the United States. From 1987 to 1989 there was a 100% increase in the reported number of cases of cumulative trauma illness (Bureau of Labor Statistics 1990). Shoulder region pain ranks second only to low back and neck pain in clinical frequency, and the occurrence of occupational shoulder illness is on the rise. This paper summarizes findings of a subset of recent epidemiologic, laboratory, and field studies conducted in order to identify occupational risk factors for cumulative trauma disorders (CTDs) of the shoulder region. These studies have identified the following risk factors as being associated with particular shoulder pain syndromes: awkward or static postures, heavy work, direct load bearing, repetitive arm movements, working with hands above shoulder height, and lack of rest. The paper begins with a discussion of several shoulder disorders, includes problems in studying cumulative trauma, presents results of recent studies, and concludes with suggested ergonomic controls that could help to reduce the incidence of shoulder disorders, by eliminating or reducing exposure to the associated risk factors.     

Low back pain and other work-related musculoskeletal problems among physiotherapists

This technical note reports the findings of a self-administered questionnaire regarding low back pain (LBP) and other musculoskeletal problems completed by 113 physiotherapists (15% of the active physiotherapists in the Republic of Slovenia). The study revealed that the overall incidence among the sample population of physiotherapists is 73.7% and the most prominent factor appears to be the age of the respondents. The only triggering factor for LBP within the physiotherapy profession appears to be handling of dependent patients.     

Determining the minimum sampling rate needed to accurately quantify cumulative spine loading from digitized video

Cumulative low back loads have been linked to the reporting of low back pain. Traditional video-based methods used to estimate these loads are time intensive for data collection and analysis. Sampling less frequently would help to reduce the associated time and cost of this type of approach. The purpose of this study was to determine how the error in estimated cumulative low back loads is affected by reducing video sampling rate. Ten healthy male university students performed three laboratory, sagittal plane lifts of varying mass (2.3, 8.8, and 15.9 kg), speed (0.2, 0.4, 0.8 m/s), and postural demand (lift from floor to table; lower from shelf to table; lift from floor over barrier and lower to floor) while being videotaped (60 frames/s). Digitized body coordinates and anthropometrics were input into a static biomechanical model, resulting in estimates of low back compression and shear forces, and moment. Load-time histories for each condition underwent rectangular integration at 60 (gold standard), 30, 20, 15, 12, 10, 6, 5, 4, 3, 2 and 1 frames/s, resulting in estimates of low back cumulative loads. Mean relative errors with respect to 60 frames/s for all cumulative loads and all conditions were found to be below 8% at 1 frame/s, and less than 3% at 2 frames/s. In addition, analyses at sampling rates above 3 frames/s were not significantly different than the cumulative loads determined at 60 frames/s, for all conditions. The accuracy of cumulative loads exhibited even at low sampling rates can be attributed, in part, to the fact that overestimations and underestimations of the integrated loads tend to cancel out over the length of the tasks considered.     

Low back pain among mineworkers in relation to driving,cold environment and ergonomics

Objectives: We aimed to study the association between low back pain (LBP) and exposure to low temperature, wet clothes, heavy lifting and jobs that involve whole body vibration (WBV) in a population of miners. Methods: Health and personal data were collected in a population study by a questionnaire. A total of 3530 workers from four mines participated in the study. Results: 51% of the workers reported LBP within the last 12 months. The adjusted odds ratio for LBP was above unity for working with wet clothes (1.82), working in cold conditions (1.52), lifting heavy (1.54), having worked as a driver previously (1.79) and driving Toro400 (2.61) or train (1.69). Conclusion: Wet clothing, cold working conditions, heavy lifting, previous work as a driver and driving certain vehicles were associated with LBP, but vehicles with WBV levels above action value were not. For better prevention of LBP, improved cabin conditions and clothing should be emphasised.     

Work organization and Low back pain in nursing personnel

Nursing personnel are at a high risk from occupational low back injury. Work organization has been suggested as one factor playing a part in the aetiology of occupational low back pain. Baseline data for a prospective epidemiology study were gathered by means of a questionnaire. One part of the questionnaire elicited characteristics of work organization, perceived autonomy, the relationship with head nurse and satisfaction in the relationship with co-workers. Information on history of musculoskeletal problems, reported frequency of lifting and personal characteristics was also gathered. Of 787 nursing staff at two acute care hospitals, 154 (19-6%) reported troublesome low back pain occurring within the previous 6 months. From univariate analyses, such characteristics of work organization as shift, type of schedule and primary versus functional nursing were not associated with low back pain. The relationship with head nurse and perceived autonomy of the job also were not related to recent back pain. Recent low back pain was significantly associated with younger age, the job category ‘registered nurse’ and greater satisfaction in relationships with co-workers. These associations were confirmed in multivariate analysis. None of the work organization factors examined, with the exception of satisfaction with co-workers, were associated with back pain in this study. Moreover, the positive association of satisfaction with coworkers suggests that interventions to improve working relationships may not be helpful in prevention programmes. To some extent, these results are susceptible to biases resulting from selective attrition from nursing and selective participation in the study.     

Prevalence and associated risk factors of low‐back pain in textile fishing net manufacturing

This study examined the 7‐day prevalence of low‐back pain (LBP; i.e., pain within the preceding week of the survey) and identified associated factors, including working posture, for a population of fishing net assembly workers. LBP is a serious problem in manual work with high prevalence and affects worker absenteeism. A cross‐sectional survey study was conducted among textile fish net industrial workers using a structured questionnaire (hand delivered by researchers and independently completed by workers). The 7‐day prevalence of LBP in this study was 68.6% (95% confidence interval [CI]: 65 to 72%). Work factors significantly related to LBP included prolonged standing and walking. Workers 35 years old or greater were significantly more likely to experience LBP within the past 7 days preceding the survey than were those 34 years old or less (adjusted odds ratio [ORadj] = 4.9; 95% CI: 2.4 to 10.3; p = .0001). Other significant factors associated with LBP included posture position, specifically stooping (ORadj = 1.6; 95% CI: 1.0 to 2.3; p = .033), lifting (ORadj = 1.6; 95% CI: 1.1 to 2.4; p = .025), and high concentration jobs (ORadj = 1.9; 95% CI: 1.3 to 2.7; p = .001), respectively. LBP among textile fish net workers is a serious problem meriting ergonomic evaluation and design of control measures for reducing worker exposure to risk factors. Work characteristics were more significantly associated with LBP than were individual characteristics. Factories need to consider adjusting work conditions to prevent worker low‐back injuries. © 2012 Wiley Periodicals, Inc.     

Shoulder muscular activity in individuals with low back pain and spinal cord injury during seated manual load transfer tasks*

This study aimed to compare the activity of four shoulder muscles in individuals with low back pain (LBP), spinal cord injuries (SCI) and a control group, during one-handed load transfer trials. Nine individuals with minimum one-year of LBP, eleven with thoracic/lumbar SCI and nine healthy controls participated in this study. The activations of anterior deltoid, upper trapezius, infraspinatus and pectoralis major were recorded by surface EMG during one-handed transferring of a cylinder from a home shelve to six spatially distributed target shelves. The integrated EMG values were compared using repeated measure ANOVA. Both LBPs and SCIs had higher anterior deltoid activation and LBPs required more upper trapezius activation than controls (p < 0.05). The spatial position of the targets also significantly influenced demands for these two muscles. The anterior deltoid and upper trapezius in LBP and SCI individuals are under higher demand during occupational load transfer tasks.

Practitioner Summary: This study aimed to compare the activation of four shoulder muscles in individuals with low back pain, spinal cord injuries and healthy condition. EMG analysis showed that the injured groups required more upper trapezius and anterior deltoid activation during load transfer tasks, which may predispose them to muscle overexertion.     

Modeling the influence of individual and employment factors on musculoskeletal disorders in fabrication industry

This study was designed to identify the individual and employment factors that influence highly frequent, less severe self‐reported musculoskeletal disorder pain incidences among welders. A self‐reporting questionnaire to measure two individual factors (age and experience), six employment factors (physical workload, working hours, shift work, nature of employment, mode of apprenticeship training, and association with present employer), along with a modified Nordic questionnaire response sheet was used to collect data. The survey was conducted among welders employed in a fabrication cluster in a southern part of India. A total of 987 completed questionnaires (response rate: 66%) were analyzed using the SPSS program. The analysis showed that two employment factors, “shift work” and “mode of apprenticeship training” significantly influence self‐reported musculoskeletal disorder pain. The mode of apprenticeship training was found to influence musculoskeletal disorder pain in the neck region for annual prevalence and causes annual disability in neck and upper back regions. Similarly, shift work was found to influence musculoskeletal disorder pain in the shoulder and neck regions for weekly and annual prevalence and causes annual disability in shoulder, wrist/hands, upper back, and hip/thigh/buttock regions among welders. These factors can be considered as points for targeting intervention efforts.