Occupational Lifting Research Articles

Pelvic positions during lifting, a multi factor analysis

The study is dedicated to the evaluation of the pelvic movements during the common acts involved in occupational lifting. Pelvic kinematics in terms of angular rotation has been analyzed in a controlled set of experiments under three methods of lifting while performing various lifting assignments, by male and female subjects. The study was designed to evaluate positioning differences in anatomical geometry due to subject gender, object's weight and reach to object distances. Measurements of angular displacements describe the geometrical motion of the pelvic during five phases of the lifting act. Analysis of the variance was performed on angular displacement, as recorded for each lifting assignment. The findings are discussed in two modes, one for different values of lifting weights, and the other for different horizontal reach distances. The paper presents an analysis of the factors affecting the performance of lifting, which contributes to the effort directed toward prevention of back injury. Relevance to industry The analysis of angular displacement in the human pelvic during the lifting act is important for the study of low-back pain and safety in manual materials handling.

Osteoarthritis of the hip and occupational lifting.

To test the hypothesis that occupational lifting is a cause of hip osteoarthritis, the authors examined associations with lifting and other occupational activities in a case-control study. The study was performed in two English health districts (Portsmouth and North Staffordshire) from 1993 to 1995. A total of 611 patients (210 men and 401 women) listed for hip replacement because of osteoarthritis over an 18-month period were compared with an equal number of controls selected from the general population and individually matched for age, sex, and general practice. Information about suspected risk factors was obtained by a questionnaire administered at interview and a short physical examination. Analysis was by conditional logistic regression. After adjustment for potential confounders, the risk in men increased progressively with the duration and heaviness of occupational lifting. Relative to those with low exposure, men who had regularly lifted weights in excess of 50 kg for 10 years or longer had an odds ratio of 3.2 (95% confidence interval 1.6-6.5). No comparable association was found in women. Of the other occupational activities examined, only frequent climbing of stairs showed a pattern suggestive of a causal relation. These findings are consistent with the results of other studies, and there is now a strong case for regarding hip osteoarthritis as an occupational disease in men whose work has involved prolonged and frequent heavy lifting.

Biomechanical risk factors for occupationally related low back disorders.

A continuing challenge for ergonomists has been to determine quantitatively the types of trunk motion and how much trunk motion contributes to the risk of occupationally-related low back disorder (LBD). It has been difficult to include this motion information in workplace assessments since the speed at which trunk motion becomes dangerous has not been determined. An in vivo study was performed to assess the contribution of three-dimensional dynamic trunk motions to the risk of LBD during occupational lifting in industry. Over 400 industrial lifting jobs were studied in 48 varied industries. The medical records in these industries were examined so that specific jobs historically categorized as either low, medium, or high risk for occupationally-related LBD could be identified. A tri-axial electrogoniometer was worn by workers and documented the three-dimensional angular position, velocity, and acceleration characteristics of the lumbar spine while workers worked at these low, medium, or high risk jobs. Workplace and individual characteristics were also documented for each of the repetitive lifting tasks. A multiple logistic regression model indicated that a combination of five trunk motion and workplace factors predicted well both medium risk and high risk occupational-related LBD. These factors included lifting frequency, load moment, trunk lateral velocity, trunk twisting velocity, and trunk sagittal angle. Increases in the magnitude of these factors significantly increased the risk of LBD. The analyses have enabled us to determine the LBD risk associated with combined changes in the magnitudes of the five factors. The results indicate that by suitably varying these five factors observed during the lift collectively, the odds of high risk group membership may decrease by over ten times. These results were related to the biomechanical, ergonomic, and epidemiologic literature. The five trunk motion and workplace factors could be used as quantitative, objective measures to redesign the workplace so that the risk of occupationally-related LBD is minimized.

The Role of Dynamic Three-Dimensional Trunk Motion in Occupationally-Related Low Back Disorders

Current ergonomic techniques for controlling the risk of occupationally-related low back disorder consist of static assessments of spinal loading during lifting activities. This may be problematic because several biomechanical models and epidemiologic studies suggest that the dynamic characteristics of a lift increase spine loading and the risk of occupational low back disorder. It has been difficult to include this motion information in workplace assessments because the speed at which trunk motion becomes dangerous has not been determined. An in vivo study was performed to assess the contribution of three-dimensional dynamic trunk motions to the risk of low back disorder during occupational lifting in industry. More than 400 repetitive industrial lifting jobs were studied in 48 varied industries. Existing medical and injury records in these industries were examined so that specific jobs historically categorized as either high-risk or low-risk for reported occupationally-related low back disorder could be identified. A triaxial electrogoniometer was worn by workers and documented the three-dimensional angular position, velocity, and acceleration characteristics of the lumbar spine while workers lifted in these high-risk or low-risk jobs. Workplace and individual characteristics were also documented for each of the repetitive lifting tasks. A multiple logistic regression model was developed, based on biomechanical plausibility, and indicated that a combination of five trunk motion and workplace factors distinguished between high and low risk of occupationally-related low back disorder risk well (odds ratio: 10.7). These factors included 1) lifting frequency, 2) load moment, 3) trunk lateral velocity, 4) trunk twisting velocity, and 5) the trunk sagittal angle. This analysis implies that by suitably varying these five factors observed during the lift collectively, the odds of high-risk group membership may decrease by almost 11 times. The predictive power of this model was found to be more than three times greater than that of current lifting guidelines. This study, though not proving causality, indicates an association between the biomechanical factors and low back disorder risk. This model could be used as a quantitative, objective measure to design the workplace so that the risk of occupationally-related low back disorder is minimized.

Industrial Quantification of Occupationally-Related Low Back Disorder Risk Factors

Few assessment technigues have attempted to define the role of occupational trunk motion in the risk of occupationally-related low back disorder (LBD) even though laboratory studies have indicated that motion significantly Increases spine loading. An in-vivo study was performed to assess the contribution of three- dimensional dynamic trunk motions to the risk of LBD during occupational lifting in industry. Over 400 industrial lifting jobs were studied in 48 industries. Specific manual materials handling jobs historically identify as either high risk or low risk for LBD were identified. A tri-axial electrogoniometer was worn by workers and documented the three-dimensional trunk motion characteristics associated with these high risk or low risk jobs. Workplace characteristics such as load moment arm, load weight, etc. were also documented for each of the repetitive lifting tasks. A multiple logistic regression model indicated that a combination of five trunk motion and workplace factors (lifting frequency, load moment, trunk lateral velocity, trunk twisting velocity, and trunk sagittal angle) predicted occupational-related LBD risk well. The analyses have enabled us to determine the LBD risk associated with combined changes in the magnitudes of the five factors. This model could be used as a quantitative, objective measure to redesign the workplace so that the risk of occupationally-related LBD is minimized.

Occupational lifting by nursing aides and warehouse workers.

Nursing aides (18 women and six men) at one traditional and one modern geriatric ward, and warehouse workers (16 men) at two different types of warehouse departments were studied during occupational work. The vertical load during manual handling was measured using strain gauges built into wooden shoes. The warehouse workers performed four times as many lifts as the nursing aides and transferred five times as great a mass per unit time. Less than 25% of the lifts were carried out with the load evenly distributed on both feet during both the upward lift and lowering. In the warehouses the lifts were short, while the nursing aides were exposed both to lifts of longer duration and to carrying, as well as a greater frequency of unexpected, sudden and high peak load. The heart rate and oxygen uptake values recorded were relatively low, and both groups utilized approximately 25% of their maximum aerobic power. According to official occupational injury statistics, both warehouse workers and nursing aides belong to risk groups with a high frequency of reported back injuries. However, more injuries are reported by nursing aides than by warehouse workers. Greater muscle strength in male workers may partly explain this difference. Qualitative differences in the design of the lifting work, with more lifts of long duration in awkward work postures, more carrying, more exertion of horizontal forces and a greater frequency of unexpected rapid lifts in the nursing aides may also contribute to the differences in risk of injury between these occupational groups. Considerable differences were found between the two hospital wards as regards lifting frequency, force, duration and the proportion of lifts with an even distribution of load on both feet during upward lift. The lifting work was approximately 50% less in the modern ward, which has easily maneuvered electric overhead hoists, spacious premises and better work organization than in the traditional ward, even though the patient handling needs were equivalent. In the warehouse department at which the wares were stored with easy access, the frequency of lifts with an even distribution of load on both feet was approximately 25%, compared to 7% in the other warehouse department. In conclusion, evaluations of occupational lifting work should include a quantitative assessment of the duration and load distribution of lifting, as well as of postures. Workstation design, technical aids and work organization have a profound effect on the lifting work load even in jobs with equal manual handling demands.

Chemical Radiculitis

Chemical radiculitis is an inflammatory condition of the nerve root due to the rupture of the annulus fibrosus and dissemination of disk fluid along the nerve root sheath. The inflammatory component of disk fluid is glycoprotein. The inflammation is a reaction to repeated injuries of the spinal column, as for example, in occupational lifting of heavy loads. Rupture of the annulus fibrosus and liberation of disk fluid into the tissues also evokes circulating antibody response and auto immune reaction. A high titer to glycoprotein at 3 weeks after an acute attack of back pain is evidence of the presence of a significant disk lesion. In selected cases immediate relief from pain occurs after administration of cortisone or a suitable cortisone-derivative. Prolonged rest may be contraindicated because of the risk of formation of radicular adhesions.