Current American football helmet design has a rigid exterior with a padded interior. Softening the hard external layer of the helmet may reduce the impact potential of the helmet, providing extra head protection and reducing its use as an offensive device. The objective of this study is to measure the impact reduction potential provided by external foam. We obtained a football helmet with built-in accelerometer-based sensors, placed it on a boxing mannequin and struck it with a weighted swinging pendulum helmet to mimic the forces sustained during a helmet-to-helmet strike. We then applied layers of 1.3 cm thick polyolefin foam to the exterior surface of the helmets and repeated the process. All impact severity measures were significantly reduced with the application of the external foam. These results support the hypothesis that adding a soft exterior layer reduces the force of impact which may be applicable to the football field. Redesigning football helmets could reduce the injury potential of the sport.
Keywords: Injury prevention, concussion, football helmet, sports injuries, head trauma
Introduction
In American football, players at all levels of competition have sustained significant head injuries.1–4 While professional and collegiate football are the most visible aspects of this sport, children and adolescents in youth and high school leagues vastly outnumber the professional and collegiate athletes.1–4 Football helmets are designed to protect the head. The current design has a rigid exterior with a padded interior. Substantial impact occurs through helmet-to-helmet, helmet-to-field, and even helmet-to-body contact.1,3,5Of particular concern is when players “lead” with their helmets, using them for offensive purposes.6,7This can cause injury to both players involved in the impact. Since players perceive that the helmet protects them, this could potentially encourage them to use the helmet as a striking force since it hurts the other player but does not hurt the originating player resulting in a harder hit. This factor has led to specific penalties against this practice. This penalty is part of modern football. In the days of leather helmets, such a penalty was not necessary, presumably because these leather helmets did not have the same hard strike potential. Paradoxically, the change to a harder helmet to protect the players, might actually increase their concussion risk if it encourages players to use their helmets in this way. New helmet designs have focused on reducing the injury potential of the helmet, but most of the efforts have focused on modifying/improving the interior of the helmet.8 Helmet designers focusing on impact reduction are currently in need of more data to create safer helmets.9 While internal helmet design can reduce the potential for injury, the hardness of the outer portion of the helmet promotes its use as a striking force. Football is a contact sport, thus making “contact”, is part of the sport. Softening the contact reduces the incentive to use the helmet as a striking force. Our hypothesis is that adding a soft cushion layer to the exterior of the helmet will reduce the impact potential of the helmet. This would have two benefits: (1) Additional head protection, (2) Eliminating the external hardness of the helmet removing the incentive to use the helmet to inflict a hard hit on opposing players. The purpose of this study is to investigate the effect of exterior protective material on the magnitude of the helmet impact force.
Methods
This helmet study was an experimental design involving no human subjects. A commercial product made by football helmet manufacturer Riddell (Elyria, OH) measures complex impact characteristics via accelerometer-based sensors built into the helmet coupled with its patented Head
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