Kinematic and dynamic biomechanical values in relation to muscle activity during contact head impact.

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 contact impact.

MATERIALS AND 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 5.61 g for non-visual and 5.03 g for visual. HIC36 was 6.65 non visual and 5.97 for visual. 3-ms criterion was 5.37 g for non-visual and 4.89 g for visual and max. force was 291 N for non-visual and 314 N for visual. The average time of muscle activation of the observed group without visual perception is 0.355 s after hitting an obstacle, with visual perception 0.085 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 10% for visual. We can conclude that the visual perception means a significant increase in pre-activation of the observed muscle group of almost 745% and lower activation in following phase of approximately 90%.