Head acceleration during impacts on snow: evaluation of a ski helmet

Current standards require ski helmets to meet acceleration criteria during impacts to a rigid surface, but do not require helmets to be evaluated for head impacts to snow, which is a common cause of traumatic brain injury in skiing and snowboarding. The objective of this study is to measure head linear acceleration during impacts to snow, with and without a ski helmet.

A portable test bench was developed and used to perform drop test of an instrumented headform onto groomed ski slopes. Impacts were made on the top of the head with and without a helmet, at three speeds (5.3 ​m/s, 6.1 ​m/s, 7.5 ​m/s) and on three types of snow (soft, hard, very hard). Head linear acceleration, HIC, snow hardness, and penetration of the head into the snow were recorded. Statistical analysis was performed using factorial ANOVAs.

96 impacts were performed. The mean peak head linear acceleration was 51G (±6G), 106G (±29G), and 170G (±27G) on soft, hard, and very hard snow, respectively, at 6.1 ​m/s. Head acceleration and HIC exceeded published thresholds for concussion and skull fracture in 85 and 28 impacts respectively. Head linear acceleration significantly increased with impact speed (p ​< ​0.001) and snow stiffness (p ​< ​0.001), but helmet use did not significantly reduce acceleration. The helmeted headform penetrated less into the snow than the non-helmeted headform.

Helmet use did not significantly reduce head linear acceleration for the snow conditions tested. The study suggests that head-snow impact characteristics should be considered in the design and evaluation of future helmets.