Exposure to whole-body vibration and mechanical shock: a field study of quad bike use in agriculture.

OBJECTIVES: The purpose of this study was to determine exposure to whole-body vibration (WBV) and mechanical shock in rural workers who use quad bikes and to explore how personal, physical, and workplace characteristics influence exposure. METHODS: A seat pad mounted triaxial accelerometer and data logger recorded full workday vibration and shock data from 130 New Zealand rural workers. Personal, physical, and workplace characteristics were gathered using a modified version of the Whole Body Vibration Health Surveillance Questionnaire. WBVs and mechanical shocks were analysed in accordance with the International Standardization for Organization (ISO 2631-1 and ISO 2631-5) standards and are presented as vibration dose value (VDV) and mechanical shock (S(ed)) exposures. RESULTS: VDV(Z) consistently exceeded European Union (Guide to good practice on whole body vibration. Directive 2002/44/EC on minimum health and safety, European Commission Directorate General Employment, Social Affairs and Equal Opportunities. 2006) guideline exposure action thresholds with some workers exceeding exposure limit thresholds. Exposure to mechanical shock was also evident. Increasing age had the strongest (negative) association with vibration and shock exposure with body mass index (BMI) having a similar but weaker effect. Age, daily driving duration, dairy farming, and use of two rear shock absorbers created the strongest multivariate model explaining 33% of variance in VDV(Z). Only age and dairy farming combined to explain 17% of the variance for daily mechanical shock. Twelve-month prevalence for low back pain was highest at 57.7% and lowest for upper back pain (13.8%). CONCLUSIONS: Personal (age and BMI), physical (shock absorbers and velocity), and workplace characteristics (driving duration and dairy farming) suggest that a mix of engineered workplace and behavioural interventions is required to reduce this level of exposure to vibration and shock.

All terrain vehicle loss of control events in agriculture: contribution of pitch, roll and velocity.

All terrain vehicle (ATV) (i.e. quad bike) loss of control (LOC) events are a major cause of injury and death on New Zealand and Australian farms. ATV LOC history, work experience, anthropometric data and vehicle pitch, roll and velocity data were recorded from 30 farmers. The terrain induced 95th percentiles were forward pitch 27.8 degrees , backward pitch 28.7 degrees and 20.8 degrees for left and right roll. Nineteen participants (mean 42.4 years) had experienced 53 LOC events and were on average 9.5 years younger than the 11 participants (mean 51.9 years) who had not previously experienced LOC. Peak pitch, roll and velocity were not associated with LOC; however, at peak left roll the non-LOC group had a pitch of 3.1 degrees downhill, while the LOC group had a pitch of 2.1 degrees uphill. Results indicate ATV LOC prevalence is considerably underestimated, while increased risk for LOC may be influenced by a combination of personal, mechanical or terrain factors. The ATV pitch, roll and slope traverse data may help in the better understanding of why LOC events occur, may help in the development of safety equipment such as a tilt warning device and will contribute to national safety guidelines. STATEMENT OF RELEVANCE: Approximately 80,000 ATVs are used in rural New Zealand and ATV accidents are the single most common cause of work-related fatalities, apart from road accidents. This fieldwork research provides pitch, roll and velocity data and considers how these data might contribute to risk of ATV accidents.

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.

Three-dimensional spinal motion and risk of low back injury during sheep shearing.

Sheep shearers are known to work in sustained flexed postures and have a high prevalence of low back pain (LBP). As sustained posture and spinal movement asymmetry under substantial loads are known risk factors for back injury our aim was to describe the 3D spinal movement of shearers while working. We hypothesised that thoraco-lumbar and lumbo-sacral movement would be tri-axial, asymmetric, and task specific. Sufficient retro-reflective markers were placed on the trunk of 12 shearers to define thoraco-lumbar and lumbo-sacral 3D motion during three tasks. Thoraco-lumbar movement consistently involved flexion, left lateral flexion, and right rotation. Lumbo-sacral movement consistently involved right lateral flexion in flexion with minimal rotation. Shearers therefore work in sustained spinal flexion where concurrent, asymmetric spinal movements into both lateral flexion and rotation occur. These asymmetric movements combined with repetitive loading may be risk factors leading to the high incidence of LBP in this occupational group.

Perceptions of low back pain in people with lower limb amputation: a focus group study.

PURPOSE: This study explored the perceptions of people with a lower limb amputation as to important factors contributing to their low back pain (LBP). METHOD: Semi-structured interviews were conducted (three focus groups and two individual interviews), with 11 participants with lower limb amputation and on-going LBP. The discussions were analysed using the General Inductive Approach. RESULTS: Five major categories were identified with "uneven posture and compensatory movements" of the back perceived to be the main contributor to LBP. "Fatigue" during functional activities and "prosthesis-related factors" may affect the "uneven movements" of the back further leading to LBP. "Multiple pain conditions" (i.e. phantom limb pain, non-amputated limb pain) could influence the pain perceptions contributing to LBP. "Self-management strategies" in the form of maintaining optimal physical fitness and support from health care professionals helped to manage LBP symptoms, thereby assisted in preventing chronicity. CONCLUSION: The results suggest "uneven movements" of the back affected by "fatigue" and "prosthesis-related factors" may alter the mechanical loading of the spine during functional activities and contribute to LBP. While being physically active helped participants cope with their LBP, identifying and addressing "uneven movements" in the back during the performance of functional activities may be important to devise prevention strategies for LBP.

Intra-session and inter-day reliability of forearm surface EMG during varying hand grip forces.

Surface electromyography (EMG) is widely used to evaluate forearm muscle function and predict hand grip forces; however, there is a lack of literature on its intra-session and inter-day reliability. The aim of this study was to determine reliability of surface EMG of finger and wrist flexor muscles across varying grip forces. Surface EMG was measured from six forearm flexor muscles of 23 healthy adults. Eleven of these subjects undertook inter-day test-retest. Six repetitions of five randomized isometric grip forces between 0% and 80% of maximum force (MVC) were recorded and normalized to MVC. Intra- and inter-day reliability were calculated through the intraclass correlation coefficient (ICC) and standard error of measurement (SEM). Normalized EMG produced excellent intra-session ICC of 0.90 when repeated measurements were averaged. Intra-session SEM was low at low grip forces, however, corresponding normalized SEM was high (23-45%) due to the small magnitude of EMG signals. This may limit the ability to evaluate finer forearm muscle function and hand grip forces in daily tasks. Combining EMG of functionally related muscles improved intra-session SEM, improving within-subject reliability without taking multiple measurements. Removing and replacing electrodes inter-day produced poor ICC (ICC < 0.50) but did not substantially affect SEM.

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.

All-terrain vehicle use in agriculture: exposure to whole body vibration and mechanical shock.

Whole body vibration (WBV) and mechanical shock were measured in 12 New Zealand farmers during their daily use of all-terrain vehicles (ATVs). As per the International Organization for Standardization (ISO) guidelines for WBV exposure, frequencies between 0 and 100Hz were recorded via a seat-pad tri-axial accelerometer during 20min of ATV use. The farmers were also surveyed to estimate seasonal variation in daily ATV usage as well as 7-day and 12-month prevalence of spinal pain. Frequency-weighted vibration exposure and total riding time were calculated to determine the daily vibration dose value (VDV). The daily VDV of 16.6m/s(1.75) was in excess of the 9.1m/s(1.75) action limit set by ISO guidelines suggesting an increased risk of low back injury from such exposure. However, the mean shock factor R, representing cumulative adverse health effects, was 0.31 indicating that these farmers were not exposed to excessive doses of mechanical shock. Extrapolation of daily VDV data to estimated seasonal variations of farmers in ATV riding time demonstrated that all participants would exceed the ISO recommended maximum permissible limits during the spring lambing season, as compared to lower exposures calculated for summer, autumn and winter. Low back pain was the most commonly reported complaint for both 7 day (50%) and 12 month prevalence (67%), followed by the neck (17% and 42%) and the upper back (17% and 25%) respectively. The results demonstrate high levels of vibration exposure within New Zealand farmers and practical recommendations are needed to reduce their exposure to WBV.

The Spineangel: Examining the validity and reliability of a novel clinical device for monitoring trunk motion.

Spinal loading in excessive and repeated trunk flexion may hinder recovery from acute low back pain. The Spineangel device provides real-time patient biofeedback on trunk flexion and may facilitate recovery from lower back injury. This cross-sectional study evaluates validity and reliability of this device in the laboratory setting. Participants included 18 healthy males. Angular displacements were simultaneously obtained from a Spineangel device placed on the hip and criterion measures of hip, lumbar and total sagittal rotation, and pelvic tilt obtained via 3D Motion Analysis. Each participant repeated four movements five times in a random order (forward bending fingertips-to-knees and to mid-lower leg, full flexion, and full extension). Intraclass correlation coefficients (ICC) for Spineangel measurement of trunk motion were excellent (ICC>0.9). The coefficient of repeatability was less than 5.2 degrees in both flexion and extension. Spineangel showed the highest correlation with Motion Analysis((R)) measurement of pelvic tilt with no statistical difference between measures when bending forward to fingertips-to-knees. Given its high reliability, the Spineangel device has potential as a trunk flexion biofeedback device. Further investigation is required to see if these laboratory results can be reproduced in the clinical setting and to determine the clinical benefits of such a device.

The effect of age on lumbar range of motion: a systematic review.

A systematic review and meta-analysis to determine the effect of age on lumbar range of motion (ROM). Assessment of lumbar ROM is commonly used in spinal clinical examination. Although known to reduce with advancing age, it is unclear how this occurs across different age bands; how this compares between movement planes; and what differences exist between males and females. Ten electronic databases were searched to find studies matching predetermined inclusion criteria. Methodological quality was assessed with a quality assessment tool for quantitative studies. Evidence for effect of age on ROM in all planes was investigated with meta-analyses. Sixteen studies met inclusion criteria with results showing age-related reductions in flexion, extension and lateral flexion particularly from 40 to 50 and after 60 years of age. There was very little age effect on lumbar rotation. There is strong evidence for a non-linear age-related reduction in lumbar sagittal and coronal ROM after 40 years of age that also appears to be asymmetric in the coronal plane. These factors should be considered during the evaluation of spinal ROM in patients who present with lumbar disorders.

The influence of a back support harness on spinal forces during sheep shearing.

Previous research has classified the occupation of sheep shearing as heavy work where shearers flex their spine and hips for long periods of time, handle awkward loads and expend high amounts of energy. The aim of this research was to investigate the magnitude of spinal forces produced during the shearing phase of the work and to determine whether the use of a commercially available back support harness would reduce these forces. Following discussion on task complexity and risk of back injury with senior shearing instructors, three component tasks of the shearing phase were identified as posing high risk of injury and were prioritized for primary analysis. Although the dragging out of a sheep in preparation for shearing and an unexpected loss of animal control were also identified as being of high risk, technological and instrumentation difficulties precluded their analysis. Twelve experienced shearers were videotaped while shearing with and without the use of a back harness. Surface mounted retro-reflective markers placed on the trunk defined three linked segments: Pelvis, Lumbar and Head, Arms, and Upper Trunk (HAUT). A 3D, link segment, top down, inverse dynamics approach was used to describe the motion and to estimate forces involved during the identified tasks of shearing. The spinal force/time profiles of this sample of shearers demonstrated large compressive and shear forces for all three tasks that are close to the NIOSH and University of Waterloo action limits for compressive and shear forces respectively (McGill 1997, Yingling and McGill 1999, Marras 2000). The use of the back support harness reduced these forces by substantial and statistically significant amounts. This effect was consistent across all three tasks. The results of this study demonstrate the production of high levels of compressive and shear forces within the spine of shearers during the three shearing tasks studied and that the use of a back support harness can substantially reduce these forces. Therefore the use of a back harness may reduce the cumulative load on the spine during shearing thereby moderating damage to the articular structures. However it is not known whether the harness would protect the spine from a sudden or unexpected force.