Kumar Shrawan, Ferrari Robert, Narayan Yogesh
Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada.
Spine (Phila Pa 1976). 2005 Mar 1;30(5):536-41. doi: 10.1097/01.brs.0000154655.96696.85.
Twenty healthy volunteers were subjected to left lateral impacts, randomly looking either left or right.
The purpose of this study is to determine the response of the cervical muscles to lateral impact whiplash-type perturbations when the head is rotated at the time of impact.
A previous study of left lateral impacts with head in neutral posture suggests that the burden of impact is borne primarily by the splenius capitis muscles. In order to improve automobile designs to prevent whiplash injury, we need to understand the response of the cervical muscles to whiplash-type perturbations in less-than-ideal conditions, such as when the head is rotated to the right and at the time of lateral impact.
Bilateral electromyograms of the sternocleidomastoids, trapezii, and splenii capitis were recorded. Triaxial accelerometers recorded the acceleration of the sled, torso, and head of the participant.
For participants experiencing a left lateral impact, whether having the head rotated to the left or right at the time of impact, the muscle responses generally increased with increasing levels of acceleration (P < 0.05). The time of onset and peak electromyograph reading for most muscles progressively decreased with increasing acceleration. Overall, however, muscle responses were of low magnitude with the head rotated to the left or right. The sternocleidomastoid muscle responsible for head rotation (i.e., right sternocleidomastoid muscle when looking left) had a greater electromyograph response than its counterpart (P < 0.05). The contralateral splenius capitis and trapezius had the highest electromyograph responses. The remaining muscles showed similar levels of electromyograph responses, but even at the highest acceleration of 12.8 m/s, all generated less than 45% of their maximal voluntary contraction electromyograph reading.
Compared to a lateral impact with the volunteer's head in the neutral position, a lateral impact with head rotation to either right or left may reduce the muscle response. Further studies are needed to determine whether or not head rotation at the time of lateral impact reduces overall injury risk.
20名健康志愿者接受左侧横向撞击，撞击时随机向左或向右看。
本研究的目的是确定当头部在撞击时旋转时，颈部肌肉对横向撞击挥鞭样扰动的反应。
先前一项关于头部处于中立姿势时左侧横向撞击的研究表明，撞击的负担主要由头夹肌承担。为了改进汽车设计以预防挥鞭样损伤，我们需要了解在不太理想的条件下，如头部向右侧旋转且在横向撞击时，颈部肌肉对挥鞭样扰动的反应。
记录胸锁乳突肌、斜方肌和头夹肌的双侧肌电图。三轴加速度计记录参与者雪橇、躯干和头部的加速度。
对于经历左侧横向撞击的参与者，无论撞击时头部向左还是向右旋转，肌肉反应通常随着加速度水平的增加而增加（P < 0.05）。大多数肌肉的肌电图起始时间和峰值读数随着加速度的增加而逐渐减少。然而，总体而言，头部向左或向右旋转时肌肉反应的幅度较低。负责头部旋转的胸锁乳突肌（即向左看时的右侧胸锁乳突肌）的肌电图反应比其对应肌肉更大（P < 0.05）。对侧的头夹肌和斜方肌的肌电图反应最高。其余肌肉显示出相似水平的肌电图反应，但即使在最高加速度12.8 m/s时，所有肌肉产生的肌电图读数均小于其最大自主收缩肌电图读数的45%。
与志愿者头部处于中立位置时的横向撞击相比，头部向左或向右旋转时的横向撞击可能会降低肌肉反应。需要进一步研究以确定横向撞击时头部旋转是否会降低总体损伤风险。
