Simulation of abdominal belt effects on IAP and spinal compressive force with musculoskeletal human model

Abstract

Repeated High-G shocks and whole-body vibration (WBV) can increase the risk of fatigue and injuries in the lumbar region of the spine for crew and passengers on High-speed craft (HSC). Existing reviews have suggested the beneficial effects of abdominal belts regarding lumbar torso stabilization and spinal unloading. The paper provides a novel 3-D seated human model with a virtual belt to simulate the belt effects for occupants on HSC. The model is built with AnyBody, a commercial software for musculoskeletal simulation based on the inverse dynamics method. The belt behaves like an additional force exerted in the lumbar region, and the force magnitude has been optimized to avoid discomfort during long journeys. The belt effects have been studied with different levels of wave shock, anthropometries, and belt design parameters such as belt width and position. Wave shocks exerted on seat surface are considered to include both vertical and off-vertical (horizontal) acceleration and expressed with a half-sine pulse. The belt effects are evaluated with intra-abdominal pressure (IAP), transversus muscle activities, and spinal compressive force. The results have shown a combined increase of IAP (137% maximum) and a decrease of spinal compressive force at the L4/L5 joint (15.5% maximum) once the belt is applied under various circumstances. Transverse abdominis activity is also reduced with belt application. The belt performs best when it covers the entire lumbar region. Reduction of belt width might lead to increased muscle activity for the muscle that isn't covered by the belt, inducing over-recruited muscle. For the same belt width, belt position variations are irrelevant to the belt performance. It has been validated that the abdominal belt can significantly assist abdominal muscles and maintain a solid core during intense WBV generated in different sea states, reducing fatigue and the risk of injury to the lumbar. Therefore, the model can be a preliminary guide for designing the abdominal belt.