@article{ref1,
title="A football helmet prototype that reduces linear and rotational acceleration with the addition of an outer shell",
journal="Journal of neurosurgery",
year="2018",
author="Zuckerman, Scott L. and Reynolds, Bryson B. and Yengo-Kahn, Aaron M. and Kuhn, Andrew W. and Chadwell, Jacob T. and Goodale, Sarah E. and Lafferty, Claire E. and Langford, Kyle T. and McKeithan, Lydia J. and Kirby, Paul and Solomon, Gary S.",
volume="ePub",
number="ePub",
pages="1-8",
abstract="OBJECTIVE Amid the public health controversy surrounding American football, a helmet that can reduce linear and rotational acceleration has the potential to decrease forces transmitted to the brain. The authors hypothesized that a football helmet with an outer shell would reduce both linear and rotational acceleration. The authors' objectives were to 1) determine an optimal material for a shock-absorbing outer shell and 2) examine the ability of an outer shell to reduce linear and/or rotational acceleration. <br><br>METHODS A laboratory-based investigation was undertaken using an extra-large Riddell Revolution football helmet. Two materials (Dow Corning Dilatant Compound and Sorbothane) were selected for their non-Newtonian properties (changes in viscosity with shear stress) to develop an outer shell. External pads were attached securely to the helmet at 3 locations: the front boss, the side, and the back. The helmet was impacted 5 times per location at 6 m/sec with pneumatic ram testing. Two-sample t-tests were used to evaluate linear/rotational acceleration differences between a helmet with and a helmet without the outer shell. <br><br>RESULTS Sorbothane was superior to the Dow Corning compound in force reduction and recovered from impact without permanent deformation. Of 5 different grades, 70-duro (a unit of hardness measured with a durometer) Sorbothane was found to have the greatest energy dissipation and stiffness, and it was chosen as the optimal outer-shell material. The helmet prototype with the outer shell reduced linear acceleration by 5.8% (from 75.4 g to 71.1 g; p < 0.001) and 10.8% (from 89.5 g to 79.8 g; p = 0.033) at the side and front boss locations, respectively, and reduced rotational acceleration by 49.8% (from 9312.8 rad/sec<sup>2</sup> to 4671.7 rad/sed<sup>2</sup>; p < 0.001) at the front boss location. <br><br>CONCLUSIONS Sorbothane (70 duro) was chosen as the optimal outer-shell material. In the outer-shell prototype helmet, the results demonstrated a 5%-10% reduction in linear acceleration at the side and front boss locations, and a 50% reduction in rotational acceleration at the front boss location. Given the paucity of publicly reported helmet-design literature and the importance of rotational acceleration in head injuries, the substantial reduction seen in rotational acceleration with this outer-shell prototype holds the potential for future helmet-design improvements.<p /> <p>Language: en</p>",
language="en",
issn="0022-3085",
doi="10.3171/2018.1.JNS172733",
url="http://dx.doi.org/10.3171/2018.1.JNS172733"
}