Gender and effect of impact acceleration on neck motion.

BACKGROUND: With the opening of the fighter cockpit to women, it became imperative to expand the current database of responses of females to both sustained and impact acceleration environments. With less upper-body strength (lean body mass) than men, it was hypothesized that women would not brace their heads as effectively against the loads occurring during high G-loading in flight and during impact and escape. This scenario creates increased potential for injury, exacerbated by the changing center of gravity and weight of helmets due to technological advances (e.g., night vision, head-up displays, etc.).
METHODS: The main objective of this experimental effort was measuring the ability of subjects of both sexes to brace against an impact acceleration of -6.5 Gx or +4.0 Gy. An attempt was made to identify a correlation between such ability, static strength measurements, anthropometric measurements, or any combination thereof.
RESULTS: No correlation was found between any of the static strength or anthropomorphic parameters and the amplitude of head motion. The isometric strength measurements correlated well with the size, weight, and neck circumference of the subjects, but none of these proved useful in predicting head displacement. However, there was a strong relationship between neck force exerted just before impact and head motion in the -Gx study, and somewhat less correlation for the +Gy impacts.
CONCLUSION: It is useful to estimate resistance to impact by measuring neck strength, but only under conditions where the subject is highly motivated.