Drivers often react to an impending collision by bracing against the steering wheel. The goal of the present study was to quantify the effect of bracing on neck muscle activity and head/torso kinematics during low-speed front and rear impacts. Eleven seated subjects (3F, 8 M) experienced multiple sled impacts (Δv = 0.77 m/s; a_peak = 19.9 m/s², Δt = 65.5 ms) with their hands on the steering wheel in two conditions: relaxed and braced against the steering wheel. Electromyographic activity in eight neck muscles (sternohyoid, sternocleidomastoid, splenius capitis, semispinalis capitis, semispinalis cervicis, multifidus, levator scapulae, and trapezius) was recorded unilaterally with indwelling electrodes and normalized by maximum voluntary contraction (MVC) levels. Head and torso kinematics (linear acceleration, angular velocity, angular rotation, and retraction) were measured with sensors and motion tracking. Muscle and kinematic variables were compared between the relaxed and braced conditions using linear mixed models. We found that pre-impact bracing generated only small increases in the pre-impact muscle activity (< 5% MVC) when compared to the relaxed condition. Pre-impact bracing did not increase peak neck muscle responses during the impacts; instead it reduced peak trapezius and multifidus muscle activity by about half during front impacts. Bracing led to widespread changes in the peak amplitude and timing of the torso and head kinematics that were not consistent with a simple stiffening of the head/neck/torso system. Instead pre-impact bracing served to couple the torso more rigidly to the seat while not necessarily coupling the head more rigidly to the torso.

驾驶员通常会靠在方向盘上对即将发生的碰撞做出反应。本研究的目标是量化支撑在低速前后碰撞期间对颈部肌肉活动和头部/躯干运动学的影响。十一就座受试者（3F，8 M）有经验的多个雪橇影响（Δ v  = 0.77米/秒;一个_峰值 =19.9米/秒²，Δ吨 = 65.5 ms) 在两种情况下双手放在方向盘上：放松和靠在方向盘上。使用留置电极单侧记录八块颈部肌肉（胸骨舌骨、胸锁乳突肌、头脾、头半棘、颈半棘、多裂肌、肩胛提肌和斜方肌）的肌电活动，并通过最大自主收缩 (MVC) 水平进行标准化。头部和躯干运动学（线性加速度、角速度、角旋转和收缩）通过传感器和运动跟踪进行测量。使用线性混合模型比较松弛和支撑条件之间的肌肉和运动学变量。我们发现，与放松状态相比，冲击前支具仅产生了冲击前肌肉活动的小幅增加（< 5% MVC）。冲击前支撑并没有增加冲击期间的峰值颈部肌肉反应；相反，它在正面碰撞期间减少了大约一半的峰值斜方肌和多裂肌活动。支撑导致躯干和头部运动学的峰值振幅和时间发生广泛变化，这与头部/颈部/躯干系统的简单硬化不一致。相反，预冲击支撑用于将躯干更牢固地连接到座椅上，而不必将头部更牢固地连接到躯干上。