Background

According to a 1999 report by the U.S. Consumer Product Safety Commission (CPSC), head injuries represent approximately 14 percent of all skiing and snowboarding injuries. In a recent retrospective study of patients treated for snowboarding-related head injuries, Nakaguchi et al. (2002) found that major head injuries were most often associated with backward falls (68%) resulting in occipital impacts (66% of falls) occurring on a gentle or moderate slope. They concluded that the majority of severe snowboarding head injuries were caused by the "opposite-edge phenomenon" where the snowboarder falls backwards and contacts the occiput.

Our Work

In order to determine if the use of skiing helmets would reduce the likelihood of head injury associated with catching an edge snowboarding, Exponent biomechanical engineers conducted a two-part study. In the first part, we measured the speeds of over 250 snowboarders on beginner and intermediate slopes at Mammoth, CA. Across all locations at the resort, the average speeds of beginner and intermediate snowboarders were 17.7 kph (11.0 mph) and 28.5 kph (17.7 mph), respectively. In the second part of the study, we used an instrumented 50th percentile male Hybrid III anthropomorphic test device (ATD) to determine the head accelerations associated with a backward fall onto the occiput, both with and without wearing a helmet. For these tests, the ATD was fitted with snowboarding equipment and accelerated to the speeds associated with an intermediate snowboarder (as measured in the first part of the study). Once the ATD was at speed, the snowboard was snubbed on the back edge, simulating the "opposite-edge phenomena" and propelling the posterior aspect of the ATD head toward the snow surface or a simulated tree. Film analysis of the ATD fall kinematics demonstrated a rapid transition to whole-body angular motion at opposite edge catch. The use of a helmet reduced substantially the linear accelerations and head injury criterion (HIC) associated with head-to-ground contact on hard, icy snow and during the simulated tree contact. Also, the neck loads were reduced significantly with helmet use. These findings indicate that helmets can mitigate head-to-ground contact severity associated with a common snowboarding fall scenario, the "opposite-edge phenomenon."