Oslo Sports Trauma Research Center

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Information about project titled 'Reconstruction of head impacts in FIS World Cup alpine skiing'

Reconstruction of head impacts in FIS World Cup alpine skiing

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Project status: Published
Project manager: Sophie Steenstrup
Supervisor(s): Tron Krosshaug, Roald Bahr
Coworker(s): Kam Ming Mok, Andrew McIntosh


Introduction: Prior to the 2013/14 season the International Ski Federation (FIS) increased the helmet testing speed from 5.4 m·s-¹ to 6.8 m·s-¹ 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 meeting our inclusion criteria, among World Cup (WC) alpine skiers, and compared these to helmet homologation laboratory test requirements.

Methods: Information about head injuries was obtained through the FIS Injury Surveillance System (ISS) throughout 9 WC seasons (2006-2015). It was possible to analyse 9 helmet impacts from 7 head injury situations. We used a commercial video-based motion analysis software to estimate head impact kinematics from broadcast video. We digitized each helmet`s trajectory relative to the ski slope, and calculated the change in velocity along and normal to the slope. We extracted helmet velocity immediately before and after impact. The sagittal plane angular movement of the head was also measured using an angle measurement software.

Results: The impacts were to the back, side and top of the helmets.In 7 of 9 helmet impacts, the estimated normal-to-slope pre-impact velocity was higher than the current FIS helmet rule of 6.8 m·s-¹ (mean 8.1 (± standard deviation 0.6) m·s-¹, range 1.9 ± 0.8 m·s-¹ to 12.1 ± 0.4 m·s-¹). The 9 helmet impacts had a mean normal-to-slope velocity change of 9.7 ± 1.0 m·s-¹, range 5.2 ± 1.1 m·s-¹ to 13.5 ± 1.3 m·s-¹.The sagittal plane head angular velocity estimates indicated a large change in angular velocity (mean 43.3 ± 2.9 rad·s-¹ (range 21.2 ± 1.5 rad·s-¹ to 64.2 ± 3.0 rad·s-¹) during impact.

Conclusion: The estimated normal-to-slope pre-impact velocity was higher than the current FIS helmet rule of 6.8 m·s-¹ in 7 of 9 helmet impacts. Further research is required to understand how laboratory helmet impact tests compare to head injury situations on snow and ice.