The startle response during whiplash: a protective or harmful response?

Area of Science:

• Biomechanics
• Human Factors Engineering
• Neuroscience

Background:

• Whiplash injuries frequently occur in rear-end car collisions.
• Occupant muscle responses, including startle responses, may contribute to whiplash injury.
• The role of the startle response in head stabilization versus injury causation is unclear.

Purpose of the Study:

• To investigate whether the startle response during a simulated rear-end collision contributes to head stabilization or exacerbates injury.
• To determine if prestimulus inhibition can modulate the startle response and associated kinematics.

Main Methods:

• Three experiments were conducted involving human subjects exposed to auditory stimuli and simulated rear-end collisions.
• Prestimulus inhibition was used, varying tone intensity and interstimulus intervals.
• Neck muscle activity and head kinematics were measured during simulated collisions preceded by different auditory cues.

Main Results:

• A loud prestimulus tone (105 dB) significantly reduced sternocleidomastoid (16%) and cervical paraspinal (29%) muscle activity.
• This loud tone also decreased head retraction (17%), horizontal head acceleration (23%), and head angular acceleration in extension (23%).
• A weak prestimulus tone (85 dB) did not alter muscle activity or kinematics.

Conclusions:

• The startle response in rear-end collisions appears to be an overreaction, increasing head kinematics.
• Minimizing this overreaction through methods like prestimulus inhibition may reduce the risk of whiplash injuries.
• Findings suggest potential strategies for mitigating whiplash injury by modulating occupant responses.