The effect of impact location, velocity, and frequency on head injury criterion during ice hockey helmet drop tests.

Background: This study investigated whether differences in ice hockey helmet protection performance at varying impact velocities influence head injury risk. Methods: Linear acceleration data were recorded during drop tests on 24 ice hockey helmets by using a uniaxial accelerometer in a collision test machine under low- and ambient-temperature environments for sequential low-, medium-, and high-velocity impacts. Head injury criterion (HIC), seasonal injury risk (SIR) under different impact velocities, and total seasonal injury risk (TSIR) were calculated for each helmet location. Results: In both temperature environments, the back, front, and side locations produced higher TSIR than the top. Under low-velocity impacts, the side location produced higher SIR and HIC than the back and front. Under medium- and high-velocity impacts, the side location produced lower SIR than the back and front, or showed no difference compared to the back. Except for comparisons between the side and back/front under low-velocity impacts, SIR and HIC differences across locations were inconsistent or nonsignificant. Conclusion: These findings suggest that under low-velocity impacts, the higher HIC at the side location may be a key factor influencing head injury risk. To enhance helmet protective performance, optimizing energy absorption at the side location during low-velocity impacts is recommended.