Pre-activation and muscle activity during frontal impact in relation to whiplash associated disorders.
OBJECTIVE
For the evaluation of neck injury the relative distance was observed between a marker placed on the forehead and a marker placed on the shoulder and also by change of the angle. To compare the severity of head injury a value of maximum head acceleration was used, HIC and a 3 ms criterion. All criteria were related to the activity of musculus sternocleidomastoideus and musculus trapezius in a situation of expected or unexpected impact.


METHODS
The situation was recorded using a Qualisys system, head acceleration of probands in three axes was recorded using the accelerometer, activity of neck muscles was monitored by a mobile EMG.


RESULTS
Maximum head acceleration was 12.1 g for non-visual and 8.2 g for visual. HIC36 was 5.7 non visual and 4.0 for visual. 3-ms criterion was 11.5 g for non-visual and 7.8 g for visual. The average time of muscle activation of the observed group without visual perception is 0.027 s after hitting an obstacle, with visual perception 0.127 s before the crash.


CONCLUSIONS
Kinematic values indicate more favourable parameters for neck injuries for visual. Head injury criteria show an average decrease of about 30% for visual. We can conclude that the visual perception means a significant increase in pre-activation of the observed muscle group of almost 400% and lower activation in both following phases of approximately 40%.
Department of Anatomy and Biomechanics, Charles University in Prague, Faculty of Physical Education and Sport, Prague, Czech Republic. fantao@seznam.cz.
Ondrej
O
Fanta
Department of Anatomy and Biomechanics, Charles University in Prague, Faculty of Physical Education and Sport, Prague, Czech Republic.
Daniel
D
Hadraba
Department of Anatomy and Biomechanics, Charles University in Prague, Faculty of Physical Education and Sport, Prague, Czech Republic.
Frantisek
F
Lopot
Department of Anatomy and Biomechanics, Charles University in Prague, Faculty of Physical Education and Sport, Prague, Czech Republic.
Petr
P
Kubovy
Department of Otorhinolaryngology Head and Neck Surgery, Charles University in Prague, First Faculty of Medicine, University Hospital Motol, Prague, Czech Republic.
Jan
J
Boucek
Department of Anatomy and Biomechanics, Charles University in Prague, Faculty of Physical Education and Sport, Prague, Czech Republic.
Karel
K
Jelen
D000054:Acceleration / Q000009:adverse effects*; D000328:Adult; D001364:Awareness / Q000502:physiology; D001696:Biomechanical Phenomena; D003654:Deceleration / Q000009:adverse effects*; D004576:Electromyography; D005260:Female; D005624:Frontal Bone / Q000502:physiology; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D008297:Male; D009334:Neck Muscles / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D015599:Trauma Severity Indices; D014911:Whiplash Injuries / Q000503:physiopathology*; D055815:Young Adult