Kumar Shrawan, Ferrari Robert, Narayan Yogesh
Department of Physical Therapy, Faculty of Rehabilitation Medicine, 3-75 Corbett Hall, University of Alberta, Edmonton, Alta., T6G 2G4, Canada.
Clin Biomech (Bristol). 2004 Nov;19(9):899-905. doi: 10.1016/j.clinbiomech.2004.06.014.
Rear impacts may be offset, and may also occur with the head rotated at impact. The purpose of this study was to determine the response of the cervical muscles to increasing low-velocity rear impacts offset by 45 degrees to the subject's right, but also with the head rotated either right or left.
Twenty healthy volunteers underwent right posterolateral impacts of 4.6, 8.0, 11.0, and 13.1 m/s2 acceleration with head turned right or left. Electromyograms of the sternocleidomastoids, trapezii, and splenii capitis were recorded, as were acceleration of the sled, torso, and head of the participant.
At an impact acceleration of 13.1 m/s2, with head rotated to the right, the left sternocleidomastoid and the contralateral (to rotation) trapezius and splenius capitis generated more electromyogram activity than their counterparts (P < 0.05). Following impacts with the head rotated to the right, the left sternocleidomastoid generated 67% of its maximal voluntary electromyogram, and the right sternocleidomastoid 5% of the maximal voluntary electromyogram, whereas the remaining muscles did not generate more than 31% of the maximal voluntary contraction electromyogram. In impacts with head rotated left, the right sternocleidomastoid generated 53% of its maximal voluntary electromyogram, and the left splenius capitis and left trapezius showed more electromyogram activity than their counterparts (P < 0.05).
Head rotation in a right posterolateral impact modifies the cervical response mainly by generating an asymmetry in the paired sternocleidomastoid electromyograms. This may asymmetrically affect the risk of injury to the sternocleidomastoids. An understanding of the muscular response to rear-impacts of different types and the effect of head rotation at the time of impact is relevant to understanding the mechanism of acute whiplash injury and may be helpful to develop targeted treatments and preventative measures.
后向撞击可能是偏心的，并且也可能在撞击时头部旋转的情况下发生。本研究的目的是确定颈部肌肉对以45度向右偏移的逐渐增加的低速后向撞击的反应，同时头部向右或向左旋转。
20名健康志愿者接受了加速度分别为4.6、8.0、11.0和13.1m/s²的右后外侧撞击，撞击时头部向右或向左转动。记录了胸锁乳突肌、斜方肌和头夹肌的肌电图，以及参与者的雪橇、躯干和头部的加速度。
在撞击加速度为13.1m/s²且头部向右转时，左侧胸锁乳突肌以及对侧（与旋转方向相反）的斜方肌和头夹肌产生的肌电图活动比其对应肌肉更多（P<0.05）。在头部向右转的撞击后，左侧胸锁乳突肌产生了其最大自主肌电图的67%，右侧胸锁乳突肌产生了最大自主肌电图的5%，而其余肌肉产生的肌电图不超过最大自主收缩肌电图的31%。在头部向左转的撞击中，右侧胸锁乳突肌产生了其最大自主肌电图的53%，左侧头夹肌和左侧斜方肌的肌电图活动比其对应肌肉更多（P<0.05）。
右后外侧撞击时的头部旋转主要通过在成对的胸锁乳突肌肌电图中产生不对称来改变颈部反应。这可能会不对称地影响胸锁乳突肌的受伤风险。了解不同类型后向撞击的肌肉反应以及撞击时头部旋转的影响，对于理解急性挥鞭伤的机制是相关的，并且可能有助于制定有针对性的治疗方法和预防措施。
