# Influence of Chinstrap Stiffness on Cerebrospinal Fluid Dynamics and Brain Stress in Helmet Impacts
## 5 Conclusions  
This study establishes that chinstrap stiffness influences helmet safety during impacts, with both overly elastic and rigid designs elevating injury risks. Highly flexible straps mitigate cranial forces through energy dissipation but compromise helmet stability, while non-stretchable variants transmit undampened stress directly to vulnerable skull base regions. Critically, intermediate stiffness introduces another kind of instability, where partial coupling between the chinstrap and jaw concentrates damaging forces at bony interfaces instead of safely redistributing energy. Balancing elasticity and rigidity emerges as essential for optimizing helmet performance, preventing destabilizing force transmission pathways that exacerbate brain injury risks. The study demonstrates that chinstrap stiffness critically mediates the trade-off between energy dissipation and helmet stability during impacts. As illustrated in Figure 12, highly flexible straps reduce cranial forces via viscoelastic deformation but risk excessive displacement, while non-stretchable designs eliminate protective dampening, channeling stress into the skull base. Intermediate configurations introduce hazardous partial decoupling, where localized sliding concentrates forces at bony interfaces. These findings underscore the need for material engineering that balances elasticity (to absorb energy) and rigidity (to maintain alignment), thereby mitigating shear-induced brain injuries without destabilizing protective gear. Optimized designs must avoid the instability regime shown in Figure 12 (intermediate stiffness), which paradoxically amplifies injury risks despite partial energy absorption. While this study provides some insights into how chinstrap stiffness affects helmet safety, several limitations must be considered. The computational model omits the skin and meningeal layers, which in reality help absorb impact energy and may lower stress reaching the brain. The analysis also focuses only on linear impacts, not accounting for rotational accelerations and shear stresses that are major contributors to concussion and diffuse axonal injury. These simplifications may lead to higher predicted intracranial stresses and do not fully reflect the complexity of real-world impacts. Future work should use more anatomically complete models and include both linear and rotational impacts to improve the relevance of computational results. However, the comparative approach ensures that any systematic bias introduced by model simplifications affects all simulations equally, allowing for the relevant assessment of how changes in chinstrap stiffness alone influence intracranial stress distribution and helmet performance. Conceptualization, M.T. and H.Z. ; methodology, M.T. ; formal analysis, J.M. ; investigation, J.M., D.N. and M.B. ; writing--original draft preparation, J.M., D.N., M.B. and M.T. ; writing--review and editing, M.T. and H.Z. All authors have read and agreed to the published version of the manuscript. This study was funded by the Department of Osteopathic Manipulative Medicine at the College of Osteopathic Medicine New York Institute of Technology and a donation from the New York Thoroughbred Horsemen's Association. Not applicable. The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author. During the preparation of this manuscript, the authors employed tools to check and enhance the grammar, some of which may have been powered by AI. The authors have thoroughly reviewed and refined the output to ensure accuracy and accept full responsibility for the content of this publication. Figure 12: The biomechanical trade-offs between cranial force mitigation and helmet stability across three chinstrap stiffness configurations under simulated pitch impacts.