Work-Related Physical Factors for Low Back Pain
In the past, studies on work-related physical risk factors for low back pain either lacked quantification of the physical load or did not take potential confusion by individual and psychosocial factors into account.
A study among a working population was initiated to identify risk factors
for musculoskeletal disorders. The object of the analysis was to determine the extent to which flexion and rotation of the trunk and lifting at work are risk factors for the occurrence of low back pain. This four-year study consisted of 861 workers from 34 companies in the Netherlands with no back pain, and included complete data on the occurrence of low back pain in the three-year follow-up period. The average age of the workers was 36 years, with an age-range of 18-59, and included workers in blue-collar, white-collar and caring professions. All risk factors included in the analysis were measured at the start of the study.
Physical loads and force at work were assessed by means of video recordings. Each worker was randomly recorded four times each day for 10-14 minutes. The videos were then classified into similar groups and analyzed by researchers within that specific group. Assessments were made of the time spent in the sitting position vs. the time spent with the trunk in a minimum of 30 or 60 degrees of flexion. The categories of trunk flexion observed were defined as neutral (<30°); mild flexion (30-60°); extreme flexion (60-90°); and very extreme flexion (>90°). Assessment of the percentage of time spent was based on multimoment observations from the video recordings. The categories of trunk rotation were defined as neutral (<30°) and twisting (>30°), and were observed every 15 seconds. Assessments on the number of times workers lifted a load of at least 10-25 kilograms (kg) were based on continual recording and were extrapolated to the number of lifts per eight-hour working day. Other general health information was assessed by means of a self-administered questionnaire.
An increased risk of low back pain was observed for workers who worked with the trunk in a minimum of 60 degrees of flexion for more than 5% of the working time, for workers who worked with the trunk in a minimum of 30 degrees of rotation for more than 10% of the working time. The same was true for workers who lifted a load of at least 25 kg more than 15 times per working day.
Hoogendoorn WE, Bongers P, de Vet HCW, et al. Flexion and rotation of the trunk and lifting at work factors are risk factors for low back pain. Spine
2000:25(23), pp 3087-3092.