Comparison of Helmet Stability on Headforms and Human Subjects

The ability of a helmet to reduce injury to the wearer in the first instance depends on whether it is securely in place during the impact. A helmet may be displaced or even ejected during a crash if it has been incorrectly fastened, worn, or inappropriately sized for the wearer's head. In the current pedal and motorcycle helmet standards, the propensity of a helmet to roll off the head in a crash is tested on a standard headform by the application of static or dynamic pull loads to the rim. The objective of this study was to assess the relationship between the results of such tests and actual stability on wearers’ heads, which may be affected by various factors such as head shape, hair, helmet size chosen, and retention strap adjustment. A group of volunteers recruited for the study were asked to select a comfortable fit from a range of helmet sizes. The minimum static pull load required to displace the helmet on the wearer’s head was compared with that on the appropriate size of headform. The relationship between a helmet’s performance in the standard test and when tested on human subjects are discussed.