The role of intra-abdominal pressure (IAP) in spinal load reduction has remained controversial, partly because previous musculoskeletal models did not introduce the pressure generating mechanism. In this study, an integrated computational methodology is proposed to combine the IAP change with core muscle activations. An ideal gas relationship was introduced to calculate pressure distribution within the abdominal cavity. Additionally, based on flexible multibody dynamics, a muscle membrane element was developed by incorporating the muscular fiber deformation, inter-fiber stiffness, and volume constancy. This element was then utilized in discretizing the diaphragm and transversus abdominis, forming an IAP–muscle coupling system of the abdominal cavity. Based on this methodology, a forward dynamic simulation of spinal flexion was presented to examine the unloading effect of abdominal breathing. The results confirm that core muscle contraction during the abdominal breathing cycle can substantially reduce the forces of spinal compression together with trunk extensor muscles, and this effect is more pronounced when the IAP increase is produced by contraction of the transversus abdominis. This unloading effect still holds even with the co-activation of other abdominal muscles, providing a potential choice when designing trunk movements during weight-lifting tasks.

腹内压 (IAP) 在减轻脊柱负荷中的作用仍然存在争议，部分原因是以前的肌肉骨骼模型没有引入压力产生机制。在这项研究中，提出了一种综合计算方法，将 IAP 变化与核心肌肉激活相结合。引入理想气体关系来计算腹腔内的压力分布。此外，基于柔性多体动力学，通过结合肌肉纤维变形、纤维间刚度和体积恒定性，开发了一种肌肉膜元件。然后将该元素用于离散隔膜和腹横肌，形成腹腔的 IAP-肌肉耦合系统。基于这种方法论，提出了脊柱屈曲的前向动态模拟来检查腹式呼吸的卸载效果。结果证实，在腹式呼吸循环期间核心肌肉收缩可以显着降低脊柱压缩力以及躯干伸肌，当腹横肌收缩产生 IAP 增加时，这种效果更加明显。即使在其他腹部肌肉共同激活的情况下，这种卸载效果仍然存在，在设计举重任务期间的躯干运动时提供了潜在的选择。当腹横肌收缩导致 IAP 增加时，这种效果更加明显。即使在其他腹部肌肉共同激活的情况下，这种卸载效果仍然存在，在设计举重任务期间的躯干运动时提供了潜在的选择。当腹横肌收缩导致 IAP 增加时，这种效果更加明显。即使在其他腹部肌肉共同激活的情况下，这种卸载效果仍然存在，在设计举重任务期间的躯干运动时提供了潜在的选择。