Physiological and psychological neck load imposed by ballistic helmets during simulated military activities

The wearing of ballistic helmets commonly coordinated with a night vision device (NVD) often imposes a load to the neck of a soldier. A lighter ballistic helmet promises comfort and enhanced combat performance, but technological developments have not provided a complete solution satisfying all the requirements, including cost. Moreover, the change in munition has led to increasing demand for the attachment of more accessories to the helmet, providing advanced functions but additional weight. Therefore, the current study quantified the neck muscle strain caused by the varying weight of a ballistic helmet, particularly during simulated infantry activities with moderate neck flexion and neck extension against a head-weight in the prone position. Eight healthy males participated on four separate days. On each day, different loads were placed on the head: 0 kg (no helmet, NH) to 2.07 kg (1.5 kg helmet with a 0.5 kg night vision device, HH&NVD). The results showed that prone shooting imposed substantial muscular strain on the splenius capitis (neck extensor), resulting in a 7-9% maximal voluntary contraction depending on the overall helmet loads. In addition, a gradual increase in the subjective neck load and pain in proportion to the overall weight of the helmet assembly was noted, and the heaviest loads caused severe complaints for muscular discomfort. This paper recommends strategies for designing and developing ballistic helmets as well as further methodological issues on evaluating neck muscle strain caused by the helmet weight.