Neck muscle activity in helicopter pilots: effect of position and helmet-mounted equipment.

Background: Helicopter pilots usually work in unfavorable ergonomic positions, often with bulky head-worn equipment during flying missions. The purpose of this study was to evaluate and compare immediate muscle response in the dorsal neck muscles to different positions with a variety of head-worn equipment.

Methods: Fourteen healthy male helicopter pilots volunteered for this study. EMG activity in the upper and lower dorsal neck muscles and the trapezius muscle was measured in a laboratory situation for 5 s in different sitting positions (neutral, trunk inclined 20 degrees, neck flexed 20 degrees), including registration of a 30 degrees left and right rotation in every position; all measurements were performed while wearing a helmet, a helmet and night vision goggles (hNVG), and a helmet, night vision goggles, and counterweight (hCW), in random order.

Results: There was significant higher EMG activity in the upper neck with hNVG and hCW than with the helmet only when comparing the mean activity level of all positions. However, there was no significant difference in EMG activity between any variations of head-worn equipment when comparing activity levels during each position separately. In the upper and lower neck, respectively, there was significantly higher muscle activity during the ipsilateral rotated positions plus neck flexion and trunk inclination than in most other positions.

Conclusion: The increased load caused by different positions seems to have a greater influence on muscle activity than the increased load of the head-worn equipment, which must be considered when designing helicopter work-places.