The influence of occupation on lumbar sagittal motion and posture

The aim of this study was to determine whether sheep shearers have clinically hypothesized adaptive postural and sagittal mobility parameters of the lumbar spine and pelvis. Sixty-four shearers and 64 non-shearers, matched by age and anthropometry and surveyed for present and previous low back pain, participated in a study to determine the effects of occupation on sagittal spinal motion and posture. Lumbar and hip mobility measurements were made with a geometric CAD analysis of lateral photographs using surface reflective markers. Sagittal range of motion demonstrated similar ranges of lumbar flexion between the two groups; however, there was a marked gain in hip flexion in the shearers as well as a marked loss of lumbar extension. The shearers also demonstrated a more lordotic lower lumbar curvature compensated by a flatter (less kyphotic) mid to lower thoracic region. Shearers appear to lose lumbar extension, gain hip flexion and develop an adaptive normal stance. This adaptation appears to be independent of previous or current back pain. Conversely, lumbar extension loss in non-shearers correlates with previous back injury. A stepwise linear regression of all participants indicated that the occupation is the predominant influence on motion and posture followed by age. The implications are one of structural adaptation in this occupational group that does not appear to be correlated with back pain.