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Cervical muscle response to right posterolateral impacts.
Shrawan Kumar1, Robert Ferrari, Yogesh Narayan
1Department of Physical Therapy, Faculty of Rehabilitation Medicine, 3-75 Corbett Hall, University of Alberta, Edmonton, Alberta, Canada T6G 2G4. shrawan.kumar@ualberta.ca
Clinical Biomechanics (Bristol, Avon)
|July 6, 2004
Summary
Unexpected posterolateral impacts cause greater head and cervical muscle responses than expected impacts. This suggests a higher risk of whiplash injury in unexpected events, particularly for sternocleidomastoid and splenii muscles.
Area of Science:
- Biomechanics
- Neuromuscular responses
- Injury mechanisms
Background:
- The impact of posterolateral forces on cervical muscles is not well understood.
- Understanding these responses is crucial for whiplash injury research.
Purpose of the Study:
- To investigate head kinematics and cervical muscle electromyography (EMG) responses to unexpected versus expected posterolateral impacts.
- To determine if impact expectation influences the severity of physiological responses.
Main Methods:
- Ten healthy volunteers underwent controlled posterolateral impacts at varying accelerations (5.0-15.4 m/s²).
- Bilateral electromyography (EMG) of sternocleidomastoids, trapezii, and splenii capitis was recorded.
- Chair, torso, and head accelerations were measured during expected and unexpected impact conditions.
Main Results:
- Unexpected impacts resulted in significantly greater head accelerations.
- Sternocleidomastoid muscles showed higher EMG activity (up to 50% MVC) in unexpected impacts compared to expected ones.
- EMG responses and onset/peak times were significantly influenced by acceleration levels and impact expectation.
Conclusions:
- Cervical muscles are vital for posture control and may be vulnerable during whiplash, especially in unexpected impacts.
- Sternocleidomastoids and splenii muscles exhibit a higher response to posterolateral impacts, indicating a potential increased risk of injury.
- These findings enhance the understanding of head and neck responses to posterolateral impacts.