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 influence of a seated break on prolonged standing induced low back pain development

With the recent attention to ‘sitting disease’, health practitioners and scientists are promoting standing in the workplace to decrease sedentary time, despite a high prevalence of low back pain (LBP) development during prolonged standing. The purpose of this study was to assess how a seated break inserted between bouts of prolonged standing would influence LBP development, posture and movement. A total of 20 participants stood for 45 minutes, sat for 15 minutes and repeated this sequence while lumbar and thoracic angles were measured, and LBP visual analogue scale reports were taken. Of the sample, 55% participants reported LBP in standing. A stand to sit ratio of 3:1 did not provide lasting recovery of LBP from standing and pain developers utilised a limited range of their lumbar spine angle and increased thoracic extension, resulting in static postures that caused tissue aggravation that was not resolved after 15 minutes of sitting. Prolonged standing in the workplace has the potential to result in LBP for some workers and alternate ways to reduce sedentary time should be investigated.     

Effects of positioning optimization in an alternative computer workstation for people with and without low back pain

The aim of this study was to measure the impact of positioning optimization on typing performance and user comfort for people with and without low back pain (LBP) in alternative working postures. Participants completed a series of typing tests in each of five randomly ordered alternative working postures ranging from upright to fully supine. Typing accuracy and typing speed were recorded as were subjective measures of overall comfort and body part discomfort. The impact of positioning optimization of the monitor, keyboard, and arm supports was determined by comparing results from an “Optimized” test study protocol (n = 27) with those from a “Non-Optimized” test study protocol (n = 26). The results indicate a significant improvement in user comfort with the optimized positioning, but no significant differences in typing performance between the two test protocols. However, in both tests the slowest typing speeds occurred in the fully reclined and zero gravity working postures. Results of the user comfort scores indicated that for the Non-Optimized test, all alternative working postures were less comfortable than the upright posture. Whereas, in the Optimized test the tilted and reclined postures were comparable to the upright working posture and only the zero gravity posture was viewed as less comfortable.

Relevance to industry

Understanding the importance of position optimization for VDT operators in alternative working postures will provide valuable information toward the development of more comfortable and more accommodating computer workstations.     

The influence of individual low back health status on workplace trunk kinematics and risk of low back disorder

A case-control study was conducted to determine whether or not kinematic-based low back disorder risk measurement (Marras et al. ) of the job was significantly different for those workers suffering from recent low back injuries compared to asymptomatic controls. Two hundred low back injured workers returning to full duty work and 200 asymptomatic controls were evaluated while performing the same job. There were no statistically significant differences between the two groups on any trunk motion measures or workplace measures. Therefore, job design is dictating the kinematic motions of the torso and not the worker's low back health. In addition, there was not a significant difference in job risk estimates using the lumbar motion monitor risk model. The mean risk (and standard deviation) for the low back injured group and the asymptomatic controls was 0.502 (0.178) and 0.501 (0.193), respectively. This study suggests that trunk kinematics and subsequent risk estimates are dictated primarily by job design and not influenced by the low back health status of the worker.     

Specific flexion-related low back pain and sitting: comparison of seated discomfort on two different chairs

No study has examined the effectiveness of prescribing seating modifications according to the individual clinical presentation of people with low back pain (LBP). A dynamic, forward-inclined chair (‘Back App’) can reduce seated paraspinal muscle activation among pain-free participants. This study examined 21 participants whose LBP was specifically aggravated by prolonged sitting and was eased by standing. Low back discomfort (LBD) and overall body discomfort (OBD) were assessed every 15 min while participants sat for 1 h on both the dynamic, forward-inclined chair and a standard office chair. LBD increased significantly more (p = 0.005) on the standard office chair, with no significant difference (p = 0.178) in OBD between the chairs. The results demonstrate that, in a specific flexion-related subgroup of people with LBP, increased LBD during sitting can be minimised through modifying chair design. Mechanisms that minimise seated discomfort may be of relevance in LBP management, as part of a biopsychosocial management plan.

Practitioner summary: This study examined low back discomfort (LBD) during a typing task among people with low back pain (LBP). Sitting on a dynamic, forward-inclined chair resulted in less seated LBD than sitting on a standard office chair. Further research is required to examine the long-term effectiveness of ergonomics interventions in 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.     

Effect of prescribed sleep surfaces on back pain and sleep quality in patients diagnosed with low back and shoulder pain

The purpose of this study was to assess sleep quality and comfort of participants diagnosed with low back pain and stiffness following sleep on individually prescribed mattresses based on dominant sleeping positions. Subjects consisted of 27 patients (females, n = 14; males, n = 13; age 44.8 yrs ± SD 14.6, weight 174 lb. ±SD 39.6, height 68.3 in. ± SD 3.7) referred by chiropractic physicians for the study. For the baseline (pretest) data subjects recorded back and shoulder discomfort, sleep quality and comfort by visual analog scales (VAS) for 21 days while sleeping in their own beds. Subsequently, participants’ beds were replaced by medium-firm mattresses specifically layered with foam and latex based on the participants’ reported prominent sleeping position and they again rated their sleep comfort and quality daily for the following 12 weeks. Analysis yielded significant differences between pre- and post means for all variables and for back pain, we found significant (p < 0.01) differences between the first posttest mean and weeks 4 and weeks 8-12, thus indicating progressive improvement in both back pain and stiffness while sleeping on the new mattresses. Additionally, the number of days per week of experiencing poor sleep and physical discomfort decreased significantly. It was concluded that sleep surfaces are related to sleep discomfort and that is indeed possible to reduce pain and discomfort and to increase sleep quality in those with chronic back pain by replacing mattresses based on sleeping position.     

Participation in workplace design with reference to low back pain: a case for the improvement of the police patrol car

Thirty Canadian police officers, divided into six groups, participated in the redesign of the interior of the patrol car. Three of the groups consisted of individuals having a history of low back disease. The effect of participating in a design process on the characteristics of the final design and on the perception of the low back pain was studied in a semi-experimental setting. The participants developed a strong commitment to the participatory design process, which was reflected in their productions. The differences between participants with and without a history of a low back disease was not marked. The former tended to stress posture-related elements in their analysis and design.     

Investigating the effect of real-time spinal postural biofeedback on seated discomfort in people with non-specific chronic low back pain

A total of 24 participants with non-specific chronic low back pain (NSCLBP) sat for 2 h while their seated posture and low back discomfort (LBD) were analysed. A total of 16 pain developers (PDs), whose LBD increased by at least two points on the numeric rating scale, repeated the procedure 1 week later, while receiving postural biofeedback. PDs were older (p = 0.018), more disabled (p = 0.021) and demonstrated greater postural variability (p < 0.001). The ramping up of LBD was reduced (p = 0.002) on retesting, when sitting posture was less end-range (p < 0.001), and less variable (p = 0.032). Seated LBD appears to be related with modifiable characteristics such as sitting behaviour. Among people with sitting-related NSCLBP, the ramping up of LBD was reduced by modifying their sitting behaviour according to their individual clinical presentation. The magnitude of change, while statistically significant, was small and no follow-up of participants was completed. Further research should examine integrating biofeedback into comprehensive biopsychosocial management strategies for NSCLBP.

Practitioner Summary: The effect of real-time postural biofeedback on LBD was examined among people with LBP. Postural biofeedback matched to the individual clinical presentation significantly reduced LBD within a single session. Further research should examine the long-term effectiveness of postural biofeedback as an intervention for LBP.     

Characterization of cashier shoulder and low back muscle demands

Cashiers commonly report musculoskeletal discomfort in their shoulders, neck, and low back. This may result from excessive loading, awkward postures, insufficient rest, or task repetition. Recently, widespread introduction of reusable, consumer-supplied bags has introduced challenges in assessing exposures in this occupational group. Limited information exists on the physical demands associated with cashier work, particularly in the context of multiple bagging formats; this study was thus designed to generate a novel data set describing standard grocery packaging tasks. Twenty-five experienced cashiers completed 36 grocery packaging tasks consisting of twice performing all combinations of workload intensity (6, 20 items), workstation height (low, medium, high), and packaging type (plastic bags, reusable bags, bins). Surface electromyography (EMG) was measured bilaterally for 5 shoulder and 3 low back muscles and processed to generate integrated muscle demand for each combination evaluated. A mixed effect ANOVA was used to assess the influences of gender, intensity, package type, side, (muscles on the right or left side of the body) and workstation height on individual and total muscular demands. High workload intensity combined with several other factors to increase muscle demands, including using plastic or reusable bags for packaging and increasing workstation height. Gender and side also interacted with workload intensity to influence muscle activity. Encouraging rest breaks, the use of bins for packaging, and decreasing cashier workstation height may help reduce potentially injurious muscular effort for cashiers.     

Effect of lifting height and load mass on low back loading

The objective of this study was to quantify the effect of lifting height and mass lifted on the peak low back load in terms of net moments, compression forces and anterior–posterior shear forces. Ten participants had to lift a box using four handle heights. Low back loading was quantified using a dynamic 3-D linked segment model and a detailed electromyographic driven model of the trunk musculature. The effects of lifting height and lifting mass were quantified using a regression technique (GEE) for correlated data. Results indicate that an increase in lifting height and a decrease in lifting mass were related to a decrease in low back load. It is argued that trunk flexion is a major contributor to low back load. For ergonomic interventions it can be advised to prioritise optimisation of the vertical location of the load to be lifted rather than decreasing the mass of the load for handle heights between 32 cm and 155 cm, and for load masses between 7.5 and 15 kg. Lifting height and load mass are important determinants of low back load during manual materials handling. This paper provides the quantitative effect of lifting height and mass lifted, the results of which can be used by ergonomists at the workplace to evaluate interventions regarding lifting height and load mass.     

Neck loads and posture exposure of helicopter pilots during simulated day and night flights

This study investigated neck loads and neck postures experienced by Canadian Forces (CF) helicopter pilots during routine simulator day and night flights. During the night flights pilots’ helmets were equipped with night vision goggles (NVG) which have been implicated in the increase of neck pain amongst pilots. Pilot’s postures were determined from video recordings of their flight missions to: (1) identify the neck postures assumed during day and night flight missions, and (2) determine the amount of biomechanical cervical spine loading experienced during these flights. Neck postures and peak and cumulative cervical kinetic loading were significant different (P < 0.05) between day and night. During night flights the percentage of work cycle spent in mildly flexed posture increased significantly from 43% during day flights to 74% during night flights. As well, cumulative reaction compression values significantly increased from 583 kN s to 694 kN s. The biomechanical results lend support to previous physiological investigations of NVG use and further justify the need for guidelines associated with NVG use.

Relevance to industry

The research highlights the biomechanical demands on the neck resulting from wearing a helmet with added weight from night vision equipment. The results have direct implication to military and commercial operators required to wear night vision equipment or added weight to the head.     

An evaluation of off-axis manual forces and upper extremity joint moments during unilateral pushing and pulling exertions

This study quantified changes in off-axis manual force production and upper extremity joint moments during sub-maximal one-handed push and pull tasks. Off-axis forces in the up/down and left/right directions were quantified in the presence or absence of constraints placed upon the direction of manual force application and/or arm posture. Resultant off-axis forces of 13.1% and 9.4% were produced for pulls and pushes, respectively. Off-axis forces during pulling were oriented downwards and to the right and were associated with a decreased should flexion moment when posture was constrained. Off-axis forces in the up/down direction were minimized with increased on-axis force level. Off-axis forces during pushing tended to be oriented to the left and were associated with increased elbow flexion moment when off-axis forces were allowed. By not accounting for these off-axis forces, we may not be accurately reflecting actionable muscle- and joint-level loading characteristics derived from biomechanically-based proactive ergonomics assessment approaches.

Practitioner Summary: Constrained arm postures and directions of manual force application influence the production of off-axis forces. As inaccurate estimation of true manual forces can markedly influence actionable outcomes of proactive ergonomic assessments, this study suggests that simplification of these estimates is insufficient and potentially misleading.     

Neck/shoulder pain,habitual spinal posture and computer use in adolescents: the importance of gender

Neck/shoulder pain is a common complaint, with evidence suggesting rates in adolescence have increased in line with increased computer use. The study aimed to examine the influence of gender on relationships between computer use, habitual posture and neck/shoulder pain. Adolescents (n = 1483) participating in the 14 year follow-up of the Raine Study cohort were surveyed for computer use, habitual sitting posture and neck/shoulder pain. Females used computers less than males (52% vs. 45% used for up to 7 h per week). Females sat much more upright than males with greater anterior pelvic tilt (9.4° vs. 0.4°). Females reported a higher 1 month prevalence of neck/shoulder pain (34.7%) than males (23.1%). A multivariate model showed neck/shoulder pain risk was increased in females (OR 2.61, 95% CI 1.70–4.00) and with computer use (OR 1.19, CI 1.01–1.40). Computer use is related to neck/shoulder pain and posture in adolescents but this relationship is different in boys and girls.

Statement of Relevance: This study showed the confounding effect of gender on the relationships among computer use, posture and neck/shoulder pain and thus the need to consider genders separately in research and practice aiming to optimise young people's use of computers.     

A comparison of low back kinetic estimates obtained through posture matching, rigid link modeling and an EMG-assisted model

This study examined errors introduced by a posture matching approach (3DMatch) relative to dynamic three-dimensional rigid link and EMG-assisted models. Eighty-eight lifting trials of various combinations of heights (floor, 0.67, 1.2 m), asymmetry (left, right and center) and mass (7.6 and 9.7 kg) were videotaped while spine postures, ground reaction forces, segment orientations and muscle activations were documented and used to estimate joint moments and forces (L5/S1). Posture matching over predicted peak and cumulative extension moment (p < 0.0001 for all variables). There was no difference between peak compression estimates obtained with posture matching or EMG-assisted approaches (p = 0.7987). Posture matching over predicted cumulative (p < 0.0001) compressive loading due to a bias in standing, however, individualized bias correction eliminated the differences. Therefore, posture matching provides a method to analyze industrial lifting exposures that will predict kinetic values similar to those of more sophisticated models, provided necessary corrections are applied.     

Prevalence of back pain and characteristics of the physical workload of community nurses

Abstract

A research project is described that analyses the back pain prevalence and physical working conditions of community nurses. The purpose was to compare the position of nurses working in institutional care with the specific situation of nurses working in the private homes of their patients. The results of a questionnaire showed that the back pain prevalence was relatively high as compared to other occupations and also when compared to other health care sectors. The home care organization is influenced not only by sick leave due to back pain, but also its efficiency is hampered by nurses with back pain who continue to work. It appeared that the total sick leave incidence due to musculoskeletal disorders other than back pain exceeds that due to back pain alone. The physical exposure level not only consisted of frequent and heavy lifting and transferring of patients but also a substantial static workload was present. The onset of back pain seems to result from a gradual build up of overload reaching its maximum. A preventive approach should take these differential loading factors into account. The consequences for preventive interventions are discussed resulting in recommendations towards a (participatory) ergonomic approach. This material forms the baseline of a controlled prospective trial in home care.     

Preparation of dynamic posture and occurrence of low back pain

Abstract

Improper posture is considered as one of the causes for low back pain. This study focused attention on low back pain that occurs when people adopt a dynamic posture. Low back pain in attendants was investigated as a typical example of low back pain in a dynamic posture. When multi-dimensional quantification III was applied to the results of the investigation, low back pain was found to occur in six postural patterns: bending knee posture, the posture of lifting and holding a light object, the posture of tilting the trunk, working posture to push a cart, the posture of turning or lifting a cart, and the posture of stretching. This survey found that low back pain frequently occurred when an unexpected load was imposed on the lumbar region and experiments were conducted to simulate the unexpected loading of this region. The experimental results showed that lumbar muscular activity was not fast enough to cope with the load and resulted in an increased swaying of the trunk. This swaying was considered to induce a load on the lumbar region. It is concluded that low back pain can be prevented if an appropriate preparatory set is taken.     

Effect of backpack load on the head,cervical spine and shoulder postures in children during gait termination

Twelve boys with an average age of 9.9 years were instructed to carry backpacks that weighed 0%, 10% and 15% of their body weights (BWs) to complete planned and unplanned gait termination experiments. The craniohorizontal, craniovertebral and sagittal shoulder posture angles at the sagittal plane as well as the anterior head alignment and coronal shoulder posture angles at the coronal plane were analysed. Results revealed significantly smaller craniohorizontal and sagittal shoulder posture angles during planned gait termination and a significantly smaller sagittal shoulder posture angle during unplanned gait termination under loaded conditions compared with those at 0% BW backpacks. Furthermore, the coronal shoulder posture angles at 10% and 15% BW during planned and unplanned gait terminations were significantly larger than those at 0% BW. Therefore, subjects were more likely to have a forward head posture, rounded shoulder posture and increased lateral tilting of the shoulders during gait termination as backpack loads were increased. However, gait termination, whether planned or unplanned, did not elicit a remarkable effect on posture.