Introduction Prior to the 2013/2014 season, the International Ski Federation (FIS) increased the helmet testing speed from 5.4 to 6.8m/s for alpine downhill, super-G and giant slalom. Whether this increased testing speed reflects head impact velocities in real head injury situations on snow is unclear. We therefore investigated the injury mechanisms and gross head impact biomechanics in seven real head injury situations among World Cup (WC) alpine skiers. Methods We analysed nine head impacts from seven head injury videos from the FIS Injury Surveillance System, throughout nine WC seasons (2006-2015) in detail. We used commercial video-based motion analysis software to estimate head impact kinematics in two dimensions, including directly preimpact and postimpact, from broadcast video. The sagittal plane angular movement of the head was also measured using angle measurement software. Results In seven of nine head impacts, the estimated normal to slope preimpact velocity was higher than the current FIS helmet rule of 6.8m/s (mean 8.1 (±SD 0.6) m/s, range 1.9±0.8 to 12.1±0.4m/s). The nine head impacts had a mean normal to slope velocity change of 9.3±1.0m/s, range 5.2±1.1 to 13.5±1.3m/s. There was a large change in sagittal plane angular velocity (mean 43.3±2.9rad/s (range 21.2±1.5 to 64.2±3.0rad/s)) during impact. Conclusion The estimated normal to slope preimpact velocity was higher than the current FIS helmet rule of 6.8?m/s in seven of nine head impacts.
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