Trunk stresses in construction workers.

The incidence of low back pain in the construction industry has been investigated. Industrial accidents, particularly those occurring during material handling, generally decreased with increasing age, but vary in incidence between different trades. Frequent high trunk stresses wore found in some of the common handling techniques, and this could well account for the associated frequency of trunk injuries. Stooping lifts are generally used at present, and it is clear that proper training in handling would reduce the hazards. To establish the basis of a training scheme for the industry, a series of laboratory studies were undertaken to compare trunk stresses in various lifting techniques when handling weights at different heights relative to the body. Semi knee lifting (lifting with the knees partially flexed) was least stressful, and lateral full stoop lifting produced the greatest stresses. Truncal stress increased with increasing load and lift height for all techniques, simultaneous increases, in lift height and load weight disproportionately increasing the truncal stresses observed. A field study was also undertaken to measure the energy demands -on an operative whon using the different lifting methods. The results demonstrated that semi knee lifts and semi stooping lifts use less energy than full stoop and full knee lifts. Likewise stoop lifts whether full or semi required lower energy expenditures than those observed during bent knee lifting. The differences observed were small, indicating that the bent knee lifting methods recommended should not lead to any material increase in fatigue at work