Biomechanical risk factors for occupationally related low back disorders

Abstract

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.

Gender-Related Differences in Prevalence of Lumbopelvic Region Movement Impairments in People With Low Back Pain

“…Performance of repetitive activities, such as bending and twisting, is a known risk factor for LBP. 2,15,18,23,24,26 Principles of the physical stress theory also would suggest that an increase in frequency of movement of a specific region across the day may contribute to increased stress on biological tissues, leading to injury and eventually pain. 21 Although data suggest that people with LBP display early lumbopelvic movement with various clinical tests, 6,9,33,36 currently the factors contributing to the early movement are not fully understood.…”

Clinicians’ views on factors that trigger a sudden onset of low back pain

“…These factors can be aggregated into a smaller number of categories [9] including biomechanical factors (regular lifting, exposure to vibration, physically demanding jobs, bending and twisting, pushing and pulling heavy loads, awkward posture) [2,[7][8][9][10][11][12][13][14][15][16][17][18][19][20], psychological/psychosocial factors (job satisfaction, local support in the workplace, depression, job control, stress) [2,7,9,16,[19][20][21][22][23][24][25] and individual risk factors (sedentary lifestyle, age, smoking, gender, obesity, poor general health, marital status, pregnancy) [2,7,9,12,13,20,21,23,[26][27][28][29][30][31]. Past studies have investigated many of these factors and their relationship to LBP.…”

Association between sitting and occupational LBP

“…Laboratory studies have focused on biomechanical hypotheses to explain the association between sitting and LBP [45,47,56,74,80]. The literature on this subject is extensive, but the evidence is somewhat contradictory.…”

“…In a more recent investigation, Wilke et al [80] reevaluated the intradiscal pressure in sitting and found that, in fact, it can be lower in sitting than in erect standing. Another hypothesis is that prolonged static sitting postures may have a negative effect on the nutrition of the intervertebral disc [47]. Thus, a constantly changing position may promote the flow of fluid (nutrition) to the disc [75].…”

“…Among the occupational exposures identified, sitting is commonly cited as a risk factor in the literature, in addition to heavy physical work, heavy or frequent lifting, non-neutral postures (i.e., trunk rotation, forward bending), pushing and pulling, and exposure to whole body vibration (WBV) (i.e., motor vehicle driving) [12,20,25,31,35,37,39,47,51,53,76,79].…”