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This picture illustrates the effects on the back when a person lifts a load with a bend back posture. When a person lifts an object, the load will be counteracted by the back muscles. The spine is the fulcrum and the back muscles are in a fixed, short distance from the spine (K). As the load in front of the body is much farther from the spine (L), the stress exerted by the back will be many times higher. The ratio between L and K can be as large as 15 times or more. This can easily create excessive stress on the corresponding back muscles and on the inter-vertebral discs, which can injury the back muscles and may also result in a "slipped disc". |