Neck Muscle and Head/Neck Kinematic Responses While Bracing Against the Steering Wheel During Front and Rear Impacts.
Level 2 - randomized trial
Controlled within-subject experimental laboratory study on human volunteers.
PubMed 33215369 · doi:10.1007/s10439-020-02687-7
What was done
Eleven seated human volunteers (3 females, 8 males) underwent low-speed front and rear sled impacts (Δv = 0.77 m/s; peak acceleration = 19.9 m/s²; Δt = 65.5 ms) with hands on a steering wheel under two conditions: relaxed and braced. Intramuscular electromyography (EMG) measured unilateral activity in eight neck muscles (sternohyoid, sternocleidomastoid, splenius capitis, semispinalis capitis, semispinalis cervicis, multifidus, levator scapulae, trapezius), normalized to maximum voluntary contraction (MVC). Head and torso kinematics (linear acceleration, angular velocity, angular rotation, retraction) were tracked and analyzed using linear mixed models.
What was found
Pre-impact bracing generated only small increases in pre-impact muscle activity (< 5% MVC) compared to the relaxed condition. Bracing did not increase peak neck muscle responses during impact and reduced peak trapezius and multifidus activity by about half during frontal impacts. Bracing altered the peak amplitude and timing of torso and head kinematics, coupling the torso more rigidly to the seat rather than stiffening the head directly to the torso.
Why it matters
These findings challenge the assumption that steering wheel bracing acts as a simple stiffener of the head-neck-torso complex during crashes. This provides empirical data to refine human body computational models used in automotive safety and whiplash injury analysis.
Limits
The sample size was small (n = 11) with a male skew (8 males, 3 females). Impacts were restricted to very low speeds (Δv = 0.77 m/s) in a laboratory setting, which may not represent kinematics or voluntary muscle responses in severe, high-speed collisions. EMG was recorded unilaterally, which may miss asymmetrical bracing strategies.
Cited by
- partial Greater neck strength helps protect against cervical injury and whiplash during traumatic impacts such as motor vehicle collisions.