Abstract
Climbing is a popular form of recreation [Gerdes, E. M., Hafner, J. W. and Aldag, J. C., “Injury Patterns and Safety Practices of Rock Climbers,” J. Trauma Inj., Infect., Crit. Care, Vol. 61, No. 6, 2006, pp. 1517–1525.]. Head injuries account for the majority of climbing fatalities; while they cannot always be prevented, wearing a certified climbing helmet can reduce head trauma. Current helmet certification procedures require impact testing only to the upper two-thirds, emphasizing protection from falling objects and resulting in helmet models that have little to no energy mitigating capabilities around their lower rim. This study presents the case for developing new helmet testing protocols emphasizing energy mitigation during climbing falls that produce head injuries 12 times more frequently than falling objects. Suspension helmets, foam helmets, and hybrid foam/suspension helmets were tested in drop and pendulum tests producing impacts to the frontal, occipital, upper parietal, and apex regions using two different headforms and a whole-body, instrumented Hybrid-III dummy. Pendulum drop tests from 1.6 m were used to create frontal and parietal impacts against a vertical steel barrier. The foam helmet delivered average values that were near the injury thresholds established for the Hybrid-III [Mertz, H. J., Irwin, A. L. and Prasad, P., “Biomechanical and Scaling Bases for Frontal and Side Impact Injury Assessment Reference Values,” Stapp Car Crash J., Vol. 47, 2003, pp. 155–188.]. All other helmet and headform combinations produced average values significantly greater than the injury thresholds. Free drops at 2.0 m from an initially upright, backward leaning orientation created occipital impacts. The dummy first struck the feet, and then rotated backward striking the back of the head, producing an impact velocity 15 % higher than that computed for a non-rotating free fall. Only the foam and magnesium headform combination delivered sub-threshold values. Average Head Injury Criterion and peak accelerations from other combinations exceeded 5000 and 500 g, respectively. Pendulum impacts to the apex following 1.0 m drops produced neck compressions, tensions, and extensions that were well beyond neck injury thresholds. These results indicate that the three certified helmets tested do not adequately protect the head during moderate height falls producing impacts to the frontal and occipital rim.
