Department of Community Medicine and Rehabilitation, Physiotherapy, Umeå University, Umeå, Sweden.
Department of Radiation Sciences, Biomedical Engineering, Umeå University, Umeå, Sweden.
Spine (Phila Pa 1976). 2018 Apr 15;43(8):E482-E487. doi: 10.1097/BRS.0000000000002396.
Human volunteers were exposed experimentally to single-sided mechanical shocks (SSMS) and double-sided mechanical shocks (DSMS) while seated.
The aim of this study was to describe and contrast seated postural reactions due to SSMS or DSMS in healthy male adults.
Mechanical shocks to the body, caused when driving on irregular terrain, are suggested to be hazardous to the spine and may be associated with the reported musculoskeletal pain of the back and neck among professional drivers. However, very little is known about the characteristics of seated postural reactions and the biomechanical effects caused by mechanical shocks.
Twenty healthy male subjects (18-43 years old) were exposed while seated to 5 SSMS and 15 DSMS in lateral directions. The second acceleration in the DSMS was in the opposite direction to the first acceleration and was fast, medium, or slow depending on the speed of direction change. Surface electromyography (EMG) was recorded in muscles of the upper neck, trapezius, erector spinae, and external oblique, while kinematics were recorded with inertial sensors placed at the neck, trunk, and pelvis. Muscle activity was normalized to maximum voluntary contractions (MVCs).
The EMG amplitudes were significantly higher (0.6-1%; P < 0.001) for the fast DSMS than all other shocks. Range of motion (ROM) of the neck and trunk was greater during the DSMS than the SSMS. Evoked muscle activity was less than 2% MVC in the trapezius, less than 10% MVC in the erector spinae and upper neck, while the activity exceeded 10% MVC in the external oblique muscles.
Fast DSMS in lateral directions appear more demanding than SSMS, demonstrating augmented seated postural reactions. However, the present mechanical shocks employed did not seem to induce postural reactions with regard to ROM or muscle activity of a magnitude likely to cause musculoskeletal overload.
本研究采用人体志愿者实验暴露法，让志愿者在坐姿下接受单侧机械冲击（SSMS）和双侧机械冲击（DSMS）。
本研究旨在描述并对比健康成年男性接受 SSMS 或 DSMS 时的坐姿姿势反应。
在不平坦的地形上行驶时，对身体造成的机械冲击被认为对脊柱有害，可能与职业司机报告的背部和颈部肌肉骨骼疼痛有关。然而，对于坐姿姿势反应的特征和机械冲击引起的生物力学效应，我们知之甚少。
20 名健康男性（18-43 岁）接受了 5 次 SSMS 和 15 次侧向 DSMS 的暴露实验。DSMS 的第二次加速度与第一次加速度相反，且加速度的快慢取决于方向变化的速度。在斜方肌、竖脊肌和腹外斜肌上记录表面肌电图（EMG），同时使用惯性传感器在颈部、躯干和骨盆上记录运动学。肌肉活动以最大自主收缩（MVC）的百分比进行归一化。
与所有其他冲击相比，快速 DSMS 的 EMG 振幅明显更高（0.6-1%；P<0.001）。DSMS 时颈部和躯干的运动范围大于 SSMS。斜方肌的诱发肌肉活动小于 MVC 的 2%，竖脊肌和上颈部的小于 10%MVC，而腹外斜肌的活动超过 10%MVC。
侧向的快速 DSMS 似乎比 SSMS 要求更高，表现出增强的坐姿姿势反应。然而，目前使用的机械冲击似乎没有引起 ROM 或肌肉活动的变化，这些变化可能会导致肌肉骨骼过载。
4 级。
