Before the 2013/2014 World Cup Season, the International Ski Federation increased helmet testing speed from 5.4 to 6.8 m/s for alpine downhill, super-G and giant slalom to better protect skiers from head injury, but a recent study, “Reconstruction of head impacts in FIS World Cup alpine skiing,” published online on November 25, 2017 in the British Journal of Sports Medicine suggests that head impact velocities in real head injury situations on snow are actually higher than the current helmet rule.
Alpine Skiing Helmet Testing Should Hit the Slopes
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Sophie Elspeth Steenstrup, physiotherapist, MSc Sports Physiotherapy and Ph.D. student at the Oslo Sports Trauma Research Center in Oslo, Norway, and colleagues analyzed nine head impacts from seven head injury videos from the International Ski Federation (FIS) Injury Surveillance Systems that occurred between the years of 2006 and 2015. They used commercial video-based motion analysis software to measure head impact kinematics and used angle measurement software to measure the sagittal plane angular movement.
According to the data, in seven of nine head impacts, the estimated normal to slope pre-impact velocity was higher than the current FIS helmet rule of 6.8 m/s (mean 8.1 (±SD 0.6) m/s, range 1.9±0.8 to 12.1±0.4 m/s). The nine head impacts had a mean normal to slope velocity change of 9.3±1.0 m/s, range 5.2±1.1 to 13.5±1.3 m/s. In addition, a large change in sagittal plan angular velocity during impact was also found.
Steenstrup told OTW, “The biggest challenge with the study was obtaining high-quality videos with a sagittal view (a view from the side) of the injury situations. Because we could only obtain seven videos of good quality with a sagittal view, the sample size is limited in our study.”
She added, “In addition, at the time of the head impact, there was some snow spray and camera blurring. Coupled with limited temporal resolution (meaning we had limited frame rates of 60 and 60 Hz), it was not possible to accurately measure the kinematics during the short duration of the impact.”
“However, the image quality until the last frame before impact allowed for accurate visualisation of helmet reference points and estimation of head velocity immediately before impact, as verified by the estimates of vertical acceleration during flight.”
At this time, Steenstrup said that their results do not indicate a need to change the helmet impact velocities in FIS mandated helmet rules in alpine skiing because of the lack of information on the relationship between real world head impacts onto snow and ice and laboratory head impacts during helmet testing procedures.
“The next logical step for further research, therefore, is for the relationship between real head impacts on snow and laboratory testing on rigid anvils to be investigated further, by performing helmet testing outside on real World Cup prepared snow and ice,” she said.
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This is a fascinating development. In my practice we've seen similar outcomes with the revised protocol. The key differentiator seems to be patient selection criteria. Has anyone else noticed the correlation with BMI thresholds?
Great point. I'd push back slightly on the conclusion, the sample size in the cited study is too small to draw population-level inferences. That said, the directional signal is compelling and worth a larger RCT.
We implemented a similar approach last year. Early results are promising but we're still gathering 12-month follow-up data. Happy to share our protocol if anyone is interested.
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