The U. S. Bureau of Mines has developed a biomechanical modeling system to examine the stresses on the lumbar spine when lifting in stooped and kneeling work postures utilized by low-seam underground coal miners. This system allows Bureau researchers to digitize two videotaped views (frontal and sagittal) of underground miners performing various lifting tasks under laboratory conditions. These points are then translated into a three-dimensional coordinate system, and a link man (developed from known anthropometry of the subject) is fitted to the 3-D coordinates. The centers of mass for the various links are calculated according to the body type (rotund, muscular, thin, or median) of the subject. Compression results were estimated using a linear programming internal/external load model. The location of the L3 vertebral body center was calculated based upon anthropometric data and morphometric studies of the lumbar spine. Results of the compression and shear force analyses for restricted lifting postures are presented and discussed.
