In order to determine if helmet design can indeed be protective against concussion, one must first understand what mechanical events lead to concussions and then determine whether the helmet can mitigate those mechanical forces. A helmet with increased mass would have reduced linear head acceleration for a given force however, it may actually increase the rotational acceleration generated from an impact because there would be an increased radius over which the forces are acting. However, better energy management via an increased thickness results in a large helmet that may be unacceptable from a style, agility, or visibility standpoint. A primary goal of the attenuation layer is to decrease the peak deceleration and to increase the time duration over which the deceleration occurs this can be achieved by a thicker or more compliant layer of material which improves the energy management by reducing the peak linear deceleration upon impact.
GEARS TACTICS INJURED SERIES
Helmet design involves a series of trade-offs between optimal safety and parameters such as the thickness and other characteristics of the attenuation material, the size and mass of the helmet, comfort, and acceptability. Single-impact helmets contain materials that are frangible and deform or fracture permanently upon impact as part of their energy management strategy.
Inner shells can be made of vinyl nitrile or expanded polypropylene, and outer shells use lightweight plastics and composites for durability and protection. For example, multiple-impact helmets, such as those for hockey and football, use materials that do not permanently deform but rather compress and return to their original dimensions. Part of the difference between single-impact helmets and multiple-impact helmets lies in the materials used. Other helmets, such as those used in ice hockey, football, and lacrosse, are designed to withstand multiple impacts over a season of games and practices ( Hoshizake and Brien, 2004). Once one of these single-impact helmets has sustained an impact, it must be replaced. Some helmets, such as those used in motor sport, bicycling, and alpine skiing, are designed to attenuate a single impact. The typical helmet has a comfort liner, an impact energy attenuating liner, a restraint system, and a shell. Early helmets were designed to prevent such injuries as skull fractures as well as moderate to severe brain injuries such as focal contusions and hemorrhages. Helmets are designed to mitigate the likelihood of head injuries from an impact to the head by dissipating and distributing the energy of impact and protecting the head from penetration. Similarly, in modern medicine, although preventive measures such as screening examinations and prophylactic use of medications will not avert all disease in all individuals, such measures can decrease the risk for disease. Although it may be impossible to prevent all sports-related concussions in youth, measures can be taken to reduce the risk of these injuries. All activity involves some risk of injury. There is debate around the words “prevention” and “reduction” relative to concussions in youth sports ( Duma et al., 2013).
The chapter concludes with the committee's findings for this portion of its charge. The chapter then discusses the roles of sports rules, concussion education initiatives, and state concussion legislation in concussion awareness and prevention. The committee's information gathering for this section included the commissioning of a paper that reviews the published literature on the ability of helmets to reduce the risk of sports-related concussions in youth ( Duma et al., 2013). The chapter begins with an overview of research on the effectiveness of protective equipment for the prevention and mitigation of sports-related concussions in youth. This chapter addresses the portion of the committee's statement of task concerning the effectiveness of protection devices and equipment and sports regulations for the prevention of concussions.
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