When a person bends over to lift an object, the intra-abdominal pressure is insufficient to prevent the abdominal cavity from buckling. This paper is concerned with estimation of the extent of buckling, its effect on the bending moment capability of the abdominal cavity and the stress distributions in the abdominal muscles. Buckling decreases the bending moment capability of the abdominal cavity, increases the stresses in the oblique muscles and transversus, and reduces to zero the stress in the rectus muscles.
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