Introduction Prior to the 2013–2014 season, the International Ski Federation (FIS) increased the helmet testing speed from a minimum requirement of 5.4 to 6.8 m/s for alpine downhill, super-G and giant slalom and for freestyle ski cross, but not for the other freestyle disciplines or snowboarding. Whether this increased testing speed reflects impact velocities in real head injury situations on snow is unclear. We therefore investigated the injury mechanisms and gross head impact biomechanics in four real head injury situations among World Cup (WC) snowboard and freestyle athletes and compared these with helmet homologation laboratory test requirements. The helmets in the four cases complied with at least European Standards (EN) 1077 (Class B) or American Society for Testing and Materials (ASTM) F2040.
Methods We analysed four head injury videos from the FIS Injury Surveillance System throughout eight WC seasons (2006–2014) in detail. We used motion analysis software to digitize the helmet’s trajectory and estimated the head’s kinematics in two dimensions, including directly preimpact and postimpact.
Results All four impacts were to the occiput. In the four cases, the normal-to-slope preimpact velocity ranged from 7.0(±SD 0.2) m/s to 10.5±0.5 m/s and the normal-to-slope velocity change ranged from 8.4±0.6 m/s to 11.7±0.7 m/s. The sagittal plane helmet angular velocity estimates indicated a large change in angular velocity (25.0±2.9 rad/s to 49.1±0.3 rad/s).
Conclusion The estimated normal-to-slope preimpact velocity was higher than the current strictest helmet testing rule of 6.8 m/s in all four cases.
- Freestyle skiing
- head injuries
- injury mechanism
- helmet standards
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Contributors All authors have made substantial contributions to all of the following: (1) the conception and design of the study, acquisition of data, and analysis and interpretation of data; (2) drafting the article or revising it critically for important intellectual content and (3) final approval of the version to be submitted.
Funding The Oslo Sports Trauma Research Center has been established at the Norwegian School of Sport Sciences through generous grants from the Royal Norwegian Ministry of Culture, the South-Eastern Norway Regional Health Authority, the IOC, the Norwegian Olympic and Paralympic Committee & Confederation of Sport and Norsk Tipping AS. The FIS Injury Surveillance System is supported by the International Ski Federation and was established through a generous grant from DJO.
Competing interests None declared.
Patient consent Detail has been removed from this case description/these case descriptions to ensure anonymity. The editors and reviewers have seen the detailed information available and are satisfied that the information backs up the case the authors are making.
Ethics approval The project has been reviewed by the Regional Committee for Medical Research Ethics, South Eastern Norway Regional Health Authority, Norway, and approved by the Social Science Data Services.
Provenance and peer review Not commissioned; externally peer reviewed.