1 Mechanical Engineering Department, Stanford University , 443 Via Ortega, Room 202, Stanford, CA 94305 , USA.
2 Bioengineering Department, Stanford University , 443 Via Ortega, Room 202, Stanford, CA 94305 , USA.
J R Soc Interface. 2019 May 31;16(154):20190086. doi: 10.1098/rsif.2019.0086. Epub 2019 May 29.
It has been suggested that neck muscle strength and anticipatory cocontraction can decrease head motions during head impacts. Here, we quantify the relative angular impulse contributions of neck soft tissue to head stabilization using an OpenSim musculoskeletal model with Hill-type muscles and rate-dependent ligaments. We simulated sagittal extension and lateral flexion mild experimental head impacts performed on 10 subjects with relaxed or cocontracted muscles, and median American football head impacts. We estimated angular impulses from active muscle, passive muscle and ligaments during head impact acceleration and deceleration phases. During the acceleration phase, active musculature produced resistive angular impulses that were 30% of the impact angular impulse in experimental impacts with cocontracted muscles. This was reduced below 20% in football impacts. During the deceleration phase, active musculature stabilized the head with 50% of the impact angular impulse in experimental impacts with cocontracted muscles. However, passive ligaments provided greater stabilizing angular impulses in football impacts. The redistribution of stabilizing angular impulses results from ligament and muscle dependence on lengthening rate, where ligaments stiffen substantially compared to active muscle at high lengthening rates. Thus, ligaments provide relatively greater deceleration impulses in these impacts, which limit the effectiveness of muscle strengthening or anticipated activations.
有人认为，颈部肌肉力量和预收缩可以减少头部在头部撞击时的运动。在这里，我们使用带有 Hill 型肌肉和速率相关韧带的 OpenSim 肌肉骨骼模型来量化颈部软组织对头部稳定的相对角冲量贡献。我们模拟了 10 名受试者在放松或预收缩肌肉状态下进行的矢状伸展和侧向屈曲轻度实验性头部撞击，以及中位数美式足球头部撞击。我们估计了在头部撞击加速和减速阶段中主动肌肉、被动肌肉和韧带的角冲量。在加速阶段，在有预收缩肌肉的实验性撞击中，主动肌肉产生的抵抗性角冲量为撞击角冲量的 30%。在足球撞击中，这一比例降至 20%以下。在减速阶段，在有预收缩肌肉的实验性撞击中，主动肌肉通过 50%的撞击角冲量来稳定头部。然而，在足球撞击中，被动韧带提供了更大的稳定角冲量。稳定角冲量的重新分配是由于韧带和肌肉对伸长率的依赖性，在高伸长率下，韧带相对于主动肌肉明显变硬。因此，在这些撞击中，韧带提供了相对较大的减速冲量，这限制了肌肉强化或预期激活的效果。
