This is a guest post by Chris Gillham, who maintains http://www.cycle-helmets.com/, a rich repository of facts and statistics on Australia’s helmet law disaster.
A commentary on a new editorial from Medical Xpress editorial at https://medicalxpress.com/news/2023-04-assumptions-helmet-safety.html and the full paper at https://www.mdpi.com/2076-3417/13/7/4544.
In essence, it says padded helmets might have poor concussion outcomes because cerebrospinal fluids surrounding the brain work fine with the first head knock but can’t settle down quick enough when there’s a rapid subsequent knock, which might happen because padded helmets often bounce, so helmets should be designed to reduce this (a bit like the supposed rotation-reducing helmets that have emerged over the past decade or so costing more than the second-hand bike you’re going to buy).
The paper’s conclusion might better explain its findings …
While most studies on coup-contrecoup injuries concentrate solely on the two main phases of impact, our research highlights that additional movements are happening within a padded helmet after an initial blow—sudden stop. These smaller back-and-forth motions may seem insignificant compared to the first one; however, we showed that they can still cause serious damage. As these subsequent head movements occur, they compromise the ability of CSF inside the skull to prevent contact between the brain and skull bones. Therefore, even minor subsequent movement can lead to direct brain-to-skull contact with catastrophic consequences.
The authors conducted interviews with two individuals who experienced head injuries. While both individuals hit their heads in similar areas, one on a slow-moving bicycle and the other during a high-speed motorcycle accident, it was found that the cyclist suffered more serious concussion symptoms. It is hypothesized that this difference may be due to the hard-shell cover of the motorcycle helmet cracking upon impact and providing additional cushioning similar to soft-shell helmets. However, this remains speculative at this point. Further experimentation and studies are necessary to fully understand how different helmet designs can prevent concussions effectively. Therefore, more research is needed to determine the most effective helmet design and materials for preventing concussions. This highlights the importance of ongoing research and innovation in helmet design to ensure optimal protection for individuals engaging in high-risk activities. For more information, G. Tierney’s (2021) review provides valuable insights into the complex relationship between concussion biomechanics, head acceleration exposure and brain injury criteria in sports.
While our study provides valuable insights into the impact of padded helmets on the cushioning effect of CSF protecting the brain, there is a need for further research to explore comprehensively various types of helmets and their effectiveness in mitigating concussion incidence among military personnel and others utilizing head protective equipment. The framework established by Op’t Eynde et al. (2020) highlights the importance of helmet design modifications that could enhance safety standards for individuals participating in high-risk activities. Therefore, future studies should focus on developing advanced helmet designs that can provide better protection against head injuries and reduce long-term health consequences.
As seems to be the case whenever the helmet v concussion topic arises, the editorial and study repeat the inference that helmets help with concussion but not as much as would be liked. e.g. from the study’s introduction …
While there is no doubt about the safety offered by protective gear, concerns remain regarding how effective helmets are at preventing concussions/contusions.
In the light of the above study, and looking at USA data:
Data suggests there was an annual average of 5,236 18yo+ US cyclist concussions in 2002-2011 and 7,489 in 2012-2021, a 43.0% increase, while 18yo+ cycling participation in those timeframes increased 16.5% from an average 24,686,100 to 28,764,000.
It is beyond argument that mostly voluntary adult bike helmet wearing increased significantly in the US from 2002 to 2021.
Among 6-17yo US cyclists, concussions dropped 26.3% from 7,095 in 2002-2011 to 5,230 in 2012-2021, which sounds good except participation dropped 24.2% while lower body injuries dropped 32.2%.
To put it another way, from 2001-2010 to 2011-2020, the average total number of all-age US cyclist injuries in ED dropped 8.9% while head injuries increased 8.9% and TBI increased 34.7% (with upper body injuries dropping 11.5% and lower body injuries dropping 6.8%).
The problem isn’t how effective helmet are at preventing concussions. The problem is that helmets worsen concussions.
For a comparison of various US cyclist injury types, see Bicycle Helmet Influence in the New Millennium on United States Head, Traumatic Brain Injury, Upper and Lower Body Injury Rates (PDF)