Joint Helmet-Mounted Cueing System and Neck Muscle Activity During Air Combat Maneuvering.

BACKGROUND: The aim of the study was to determine the characteristics of cervical muscle activity in different head postures when using helmet-mounted display in one fighter vs. two aircraft air combat within visual range (WVR). METHODS: Cervical EMG was measured with eight F/A-18 pilots using the Joint Helmet Mounted Cueing System (JHMCS) during air combat maneuvering. In-flight G(z) acceleration and continuous head position were recorded. EMG activity is divided and presented in a matrix with three-class rotation and five-class flexion-extension postures. RESULTS: The mean muscle activity in sternocleidomastoids and cervical extensors was 28.9% of maximal voluntary contraction (MVC) and 44.8% MVC, respectively. Cervical flexor and extensor muscles are subjected to loading over MVC during high G(z) sorties. Cervical rotation combined with extension exceeded muscle force-producing capacity during high G(z) resulting in a decline in muscle activity. DISCUSSION: Awkward postures, especially rotational ones, are more prone to increase loading over muscles' capacity. Overloading of muscles increases the risk of muscular and ligamentous injury. In addition, the lack of muscular support potentially leads to the G(z) loading being transferred to spinal structures via intervertebral discs and the vertebral column. The JHMCS helmet seems to change the pattern of most loading muscles toward the extensor (posterior) neck muscles.