The effect of seat belt use on the cervical electromyogram response to whiplash-type impacts.
OBJECTIVE
The objective of this study was to determine the effect of a standard 3-point lap-and-shoulder seat belt and car seat on the electromyogram (EMG) response of the cervical muscles to increasing low-velocity impacts in comparison with that of a rigid seat and 5-point restraint.


METHODS
Seventeen healthy volunteers were subjected to rear, frontal, right and left lateral and bilateral anterolateral, and posterolateral impacts with an acceleration varying from 4.4 to 16.8 m/s(2) while in a car seat with lap-and-shoulder seat belt.


RESULTS
For rear-end impacts, whether straight on, right posterolateral, or left posterolateral, all muscles generated 50% or less of the maximal voluntary contraction (MVC) EMG. In straight-on rear impacts, the sternocleidomastoid was symmetrically the most active; however, in posterolateral impacts, the sternocleidomastoid contralateral to impact direction was more active than its counterpart. For a right lateral impact, at the highest acceleration, the left splenius capitis generated 47% of its MVC and the left trapezius did 46% of its MVC. In a left lateral impact, the right splenius capitis generated 48% of its MVC and the right trapezius did 57% of its MVC. In a straight-on frontal impact, the left trapezius generated 35% of its MVC and the right trapezius did 48% of its MVC. In a left anterolateral impact, the right splenius generated 60% of its MVC and the right trapezius did 66% of its MVC. Similarly, in a right anterolateral impact, the contralateral splenius muscle increased its activity to 52% of its MVC and the left trapezius was at 52% of its MVC.


CONCLUSIONS
Compared with previously reported impact studies with a rigid seat and 5-point harness, the use of a 3-point lap-and-shoulder seat belt with a standard car seat did not appear to adversely affect cervical muscle response. In very-low-velocity and low-velocity impact experiments, seat belt and seat type may not significantly alter cervical EMG and kinematics.
Kumar
Shrawan
S
Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada. shrawan.kumar@ualberta.ca
Ferrari
Robert
R
Narayan
Yogesh
Y
Jones
Troy
T
D000054:Acceleration; D000328:Adult; D004576:Electromyography; D004867:Equipment Design; D006257:Head / Q000503:physiopathology; D006801:Humans; D009119:Muscle Contraction; D009334:Neck Muscles / Q000503:physiopathology*; D012016:Reference Values; D012622:Seat Belts; D013997:Time Factors; D014911:Whiplash Injuries / Q000175:diagnosis / Q000503:physiopathology*