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BirthandevolutionofthefootballhelmetARTICLEinNEUROSURGERYOCTOBER2004ImpactFactor:3.03DOI:10.1227/01.NEU.0000134599.01917.AASource:PubMed

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LITERATURE REVIEWS

BIRTH AND EVOLUTION OF THE FOOTBALL HELMET

Michael L. Levy, M.D.,Ph.D.Division of Neurosurgery,University of California atSan Diego School of Medicine,San Diego, California

Burak M. Ozgur, M.D.Division of Neurosurgery,University of California atSan Diego School of Medicine,San Diego, California

Cherisse Berry, B.S.Keck School of Medicine,University of Southern California,Los Angeles, California

Henry E. Aryan, M.D.Division of Neurosurgery,University of California atSan Diego School of Medicine,San Diego, California

Michael L.J. Apuzzo, M.D.Department of NeurologicalSurgery, Keck School of Medicine,University of Southern California,Los Angeles, California

Reprint requests:Michael L. Levy, M.D., Ph.D.,Suite 502, 8010 Frost Street,San Diego, CA 92123.Email: [email protected]

Received, October 6, 2003.

Accepted, February 23, 2004.

OBJECTIVE: To review the advent and evolution of the football helmet throughhistorical, physiological, and biomechanical analysis.METHODS: We obtained data from a thorough review of the literature.RESULTS: Significant correlation exists between head injuries and the advent of thefootball helmet in 1896, through its evolution in the early to mid-1900s, and regulatorystandards for both helmet use and design and tackling rules and regulations. With theimplementation of National Operating Committee on Standards for Athletic Equipmentstandards, fatalities decreased by 74% and serious head injuries decreased from 4.25per 100,000 to 0.68 per 100,000. Not only is the material used important, but theprotective design also proves essential in head injury prevention. Competition amongleading helmet manufacturers has benefited the ultimate goal of injury prevention.However, just as significant in decreasing the incidence and severity of head injury isthe implementation of newer rules and regulations in teaching, coaching, and gov-erning tackling techniques.CONCLUSION: Helmet use in conjunction with more stringent head injury guidelinesand rules has had a tremendous impact in decreasing head injury severity in football.Modifications of current testing models may further improve helmet design and hencefurther decrease the incidence and severity of head injury sustained while playingfootball.

KEY WORDS: Biomechanics, Football, Head injury, Helmet, Sports injury prevention

Neurosurgery 55:656-662, 2004 DOI: 10.1227/01.NEU.0000134599.01917.AA www.neurosurgery-online.com

HISTORICAL BACKGROUND

Today, American society has declared Su-perbowl Sunday to be the biggest tele-vision event of the year. Fathers live vi-cariously through their sons by encouragingthem to play peewee football and then sup-porting their play through varsity football andperhaps, for the very few, to the professionalleagues. Part of this culture must reflect thetremendous decline in the incidence of serioushead injury and death. Perhaps, had not cer-tain changes taken place, few parents wouldbe so eager to allow their child to play such apotentially dangerous game.

Eighteen deaths and 159 serious injurieswere attributed to American football from1869 to 1905. The first documented use of ahelmet during a football game occurred dur-ing an Army-Navy game in 1893. Initial hel-mets consisted merely of leather. Replicas ofthe three main types of leather football hel-mets are shown in Figures 1, 2, and 3. Then,

with time, metal alloys were added to providemore support and protection. Helmet use didnot become mandatory for the National Col-legiate Athletic Association until 1939 and theNational Football League until 1940. Evenwith the first single-bar face mask (appearingin 1951) and the first double-bar face masks/cages (appearing in 1958), both tackling drillfatalities and head injuries continued to in-crease, whereas spine injuries decreased be-tween 1955 and 1964. The increases infootball-related injuries resulted in the pro-spective collection of injury data, which wasinitiated in 1967. As a result of the continuedincrease in head and spine injuries from 1965to 1974, rule changes were implemented. TheNational Operating Committee on Standardsfor Athletic Equipment (NOCSAE), foundedin 1969, initiated research efforts for head pro-tection and implemented the first safety stan-dards for football helmets in 1973 (1, 4, 10).

The Standard Method of Impact Test andPerformance Requirements for Football Hel-

656 | VOLUME 55 | NUMBER 3 | SEPTEMBER 2004 www.neurosurgery-online.com

mets published in 1973 required the use of a head model thatclosely simulates the response of the human head to impact.Standards are based on the helmet falling in a guided free fall.In each case, the helmet is positioned on a head form. Thehead form is human-like and complex in function and isconstructed to provide a measure of the ability of the helmetto attenuate the kinetic energy released during the test. Theenergy is based on the drop velocity and the mass of the head

form. The goal of NOCSAE was to develop a standard thatwould measure the ability of the football helmet to withstandrepeated blows of various magnitudes under a wide variety ofplaying conditions without any sacrifice in protective quality.Drawings illustrating the types of testing that helmet manu-facturers are held accountable for are provided in theNOCSAE guidelines and reproduced in Figure 4. A photo-graph of actual testing apparatus is displayed in Figure 5.Helmets must be able to endure forces occurring over multipleseasons without the need for reconditioning. Standards wereapplied to players ranging in age from 14 years to profession-als. The standards were also applied to numerous environ-mental conditions (freezing cold, driving rain, heavy snow, orhigh heat and humidity) and playing surfaces (hard-packeddirt, thick mud, deep grass, or artificial turf).

In 1975, Joseph S. Torg, then Director of Sports Medicine atTemple University, initiated a central registry for the collec-tion, documentation, and analysis of cases of severe neckinjuries occurring in football (3, 11). Torg determined thattackling techniques also played a significant role in the typesand severity of football-related injuries. At the end of the 1975season, both the National Collegiate Athletic Association andthe National Alliance Football Rules Committee enacted rulesdesigned to prevent the use of the head as the initial point ofcontact during play. The rules implemented stated that noplayer shall intentionally strike a runner with the crown or topof the helmet. Spearing is the deliberate use of the helmet in anattempt to punish an opponent, and no player shall deliber-ately use his helmet to butt or ram an opponent.

The National Alliance Football Rules Committee provisionprohibited any technique involving a blow with the face mask,

FIGURE 1. Photograph of beehive style leather football helmet.

FIGURE 2. Photograph of flat-top style leather football helmet.

FIGURE 3. Photograph of dog-ear style leather football helmet.

EVOLUTION OF THE FOOTBALL HELMET

NEUROSURGERY VOLUME 55 | NUMBER 3 | SEPTEMBER 2004 | 657

frontal area, or top of the helmet driven directly into anopponent as the primary point of contact either in close lineplay or in the open field. As a result of the prohibition ofheadfirst contact, there was a resultant decrease in head andneck injuries.

In 1977, the National Collegiate Athletic Association fundedthe initial National Survey of Catastrophic Football Injuries,which from 1982 to the present has been known as the Na-tional Center for Catastrophic Sports Injury Research underthe direction of Dr. Fred Mueller. NOCSAE established helmet

safety standards in 1978 for college football and in 1980 forhigh school football. Currently, it is mandatory for all highschool and college players to wear helmets meeting NOCSAEstandards (5).

HELMETS

The American football helmet was and is designed to pro-tect the areas of the players head directly covered by thehelmet from direct linear impact only. The helmet was not andcannot be designed to prevent injury to or protect the cervicalspine or spinal column on those areas of the neck not coveredby the helmet or to prevent injuries to the brain that resultfrom rotational acceleration. As a result of NOCSAE, criticalchanges became apparent in the protective qualities of footballhelmets beginning in the early 1970s. According to Schneider(9), football helmets should be constructed specifically on thebasis of an anatomic knowledge of the cranium and brain withan understanding of the mechanical principles involved inhead injuries. Schneider stated that the outer shell of thehelmet should be constructed to cover either the fragile areasof the cranium, which might fracture, or to cover specificportions of the intracranial contents, which are most fre-quently vulnerable to head injuries and may result in concus-sion. The firm posterior margin of the outer shell of the helmetshould be cut high to avoid potential cervical injuries. Morerecently, helmet manufacturers have focused further on theinner suspension system developed to distribute forces gen-erated by impact uniformly over the head. This system con-sists of two crowns, one within the other. Each crown is ahemisphere of hollow plastic material with arches extendingfrom the apex to the base or circumference of the crown (RCSchneider [9]). Air or gas injected through valves into thesestructures diffuses throughout all parts of each individualcrown (9). In the completed helmet, the two crowns areinjection-molded and electrically sealed together as a singlepiece by use of a high-frequency sound wave. An inner crownis inflated pneumatically to fit the individual player, but theouter crown lining the outer shell of the helmet is inflated tothe same pressure for all wearers (9). The presence of the two

FIGURE 4. Illustrations depicting testing guidelines by NOCSAE.

FIGURE 5. Photograph of helmet testing apparatus.

LEVY ET AL.


separate, pneumatically sealed systems avoids the problemsof the headgear bouncing on the head. The helmet is main-tained in position on the head with a four-point attached chinstrap.

Helmet material must allow for more deformation andgradual deceleration of the head. The face guard should beflattened, and the chin straps should release easily. The pos-terior rim of the shell should be advanced, and shoulder rollsmust be used for further craniocervical protection. Web sus-pensions absorb force at fixation points; however, isolatedfluid or air pockets should avoid supraorbital and occipitalnerves. Helmet shell material must allow for more protectionof fragile regions of the cranium and areas prone to concussiveinjury. The initial force of impact must be decreased from theathlete and the lower force distributed over larger area and alonger period of time.

Although the characteristics of energy absorption and atten-uation of blows to the helmet are of critical importance inhelmet design, many researchers think that there are manyother requirements and considerations that should not beoverlooked. Position maintenance so that no slippage occursduring wear; good ventilation; good vision so that there is norestriction of peripheral vision; light weight; a smooth, hardexterior surface; good fit to the players head; continued func-tional use after repeated blows; comfort; economics; appear-ance; ability to withstand the effects of sun, temperature,paints, or cleansers on the shell or components; and durabilityare all essential characteristics to helmet design. Helmet de-signers have attempted to incorporate all of these characteris-tics in designing protective headgear while at the same timemaximizing the linear impact absorption and attenuation ca-pabilities of the helmet.

Position maintenance and individual contour fitting are es-sential goals of any helmet. Helmet systems and design ele-ments vary considerably in their ability to satisfactorily meetthe requirements of the large variability of cranial contour andvolume. In addition, significant testing has determined that nostatistical differences were observed for comparison amonghelmeted and nonhelmeted trials for heart rate, core temper-ature, weight loss, or other physiological strain indices (6).

DESIGN

In testing helmets in 1977, Elwyn Gooding, then a researchassociate at the University of Michigan, with Richard Schnei-der, simulated the forces present during the production ofboth acute subdural hematomas and cervical spine injurieswith tetraplegia and compared the effectiveness of varioustypes of protective football headgear in attenuating theseforces. In this series of impact testing, Gooding used a bareheadform against a rigid anvil as a signal to record specifictypes of impacts. These tests were repeated with differenttypes of helmets of varying construction and under variousconditions. Gooding found that in simulating impacts to boththe occipital region of the head, known to produce subduralhematomas, and to the vertex of the head, known to produce

cervical fractures with tetraplegia, a severe brainstem contu-sion, or hemorrhage, all types of helmets attenuated the blowconsiderably compared with blows sustained by the bare headform against a plain anvil. After testing all types of web andfoam suspension systems and combined web and foam sys-tems, Gooding found that the better helmet is one that has asmall initial rise and a distribution of force at a lower peak fora longer time. Myers et al. (7) determined that helmet systemsusing pneumatic or a combination of pneumatic and foampadding systems were the most successful at absorbing en-ergy compared with purely foam or suspension-type helmets.Further comparison revealed that the double-crown pneu-matic helmet provided the best protection. Bishop et al. (2)also performed mechanical testing to demonstrate failure ratesin relation to the Gadd Severity Index for suspension-typeliners versus padded liners. They found that at a Gadd Sever-ity Index score of 1500, failure rates were 19 and 2% forsuspension-type and padded-type liners, respectively. Fur-thermore, at a Gadd Severity Index score of 1200, failure rateswere 65 and 11% for suspension-type and padded-type liners,respectively. Clearly, their study demonstrated the superiorityof padded-type liners over suspension-type liners under im-pact conditions.

Although value exists in determining compatibility withknown standards, performance in the established test meth-ods and comparisons of various helmet designs must not beused to predict the likelihood of the capability of any headgearto limit certain injuries. There is no helmet that can prevent allhead injuries.

ASSESSMENT

NOCSAE has allowed for the standardization of tests by useof performance testing of existing and novel helmets (8). Inaddition to defining the standard drop test method and equip-ment used in evaluating the performance characteristics ofprotective headgear, they also provide a laboratory proceduralguide for certifying newly manufactured football helmets anddescribing the equipment calibration procedures. Standardperformance specifications for newly manufactured footballhelmets have also been defined.

In testing helmets, at least two of each model and size mustbe tested. Helmets are tested without face guards or faceguard-specific hardware. One problem with current testing isthat sizes smaller than 658 usually will not fit the smallestNOCSAE head forms. In that event, testing of that size iswaived as long as the other sizes of that model have beentested and meet all requirements. The implementation of nu-merous sized headforms would be more appropriate. In ad-dition, to obtain a reasonable fit for testing purposes, helmetslarger than size 758 may require shim pads to be insertedbetween the largest head forms and the interior of the helmet,opposite from the impact site. Helmet manufacturers are re-quired to stamp the NOCSAE emblem and warnings on hel-mets, as demonstrated in Figure 6.



In evaluating helmet re-sponse, the GADD SeverityIndex score of any impactshall not exceed 1200. In ad-dition, helmet fit must bemaintained without inter-vention throughout the en-tire series of impacts. Anystructural changes or otherchanges that take place dur-ing impact testing that resultin loosening the fit to thehead form shall be cause for failure. Helmet repositioning duringtesting is anticipated. However, additional, unrestorable loosen-ing of the fit is not allowed.

Three companies currently provide football headgear at theNational Football League level. All have hard plastic shells,foams of various densities to attenuate linear impacts, and a fitsystem that inflates. All three helmet models use the same jawpads, chin straps, and face guards. Along with these elements,any system must allow satisfactory flexibility to fit and main-tain stability on the individual. One design has an inflatableair liner that is a continuous tube-like design. When inflated,these tubes expand to aid in the fit. The air system is nestedinto a foam system that is composed of two different densitiesand is molded to shape. The two layers are ethyl vinyl acetateand polyvinyl chloride nitrile rubber (vinyl nitrile). The frontand rear pads of similar design and the air inflation system areused for fitting.

The second helmet uses similar foam, but instead of thefoam being molded, die-cut pieces are placed in a molded casethat holds the resulting blocks of foam layers in place. Air isintroduced into the same molded case, causing the case toexpand and fit the head. In this design, the front pad is amolded urethane that fits into a sleeve. The third helmet usesa different approach. The shell is ventilated and lighter thanthe previous two. The air liner is similar to helmet 2 in con-struction but is different in shape and does not serve as aholder for the primary foam components. A unique inner linerof expanded polypropylene increases the inner shell. A foammolded ethyl vinyl acetate component with vinyl nitrile in-serts similar to helmet 1 serves as a cover to the expandedpolypropylene and a holder of the air fit system. A vinyl nitrilefront pad is provided but is not changed for fitting.

Recently, a new lightweight helmet system has been de-signed, the Pro-Edition helmet from Bike Athletic (Fig. 7). Themanufacturer boasts that the helmet has an anthropometricouter shell that better conforms to the head contours, improv-ing the fit and comfort and creating a means of deflection. Theventing system allows air to circulate and dissipate quickly. Aunique, stiff skeletal substructure effectively supports the shellconstruction and assists in attenuating impacts.

The other major manufacturer of football helmets in thiscountry is Riddell. Their most recent productions include theVSR-4 and the Revolution, which contain a combination ofadjustable inflatable liners and foam padding. The latter con-

tains their Z-pad design for an inflatable liner on the sides ofthe helmet to further protect against lateral blows to the headand face. Figures 8 and 9 display the Riddell VSR-4 and Rev-olution, respectively.

It should be stressed that these tests offer at best limitedassessment of the protective capabilities of a helmet. Thus far,no evaluation of rotational forces or repetitive endurance hasbeen performed. Despite the stringent efforts set forth over thepast 30 years to improve safety and more than 51 injuryprevention rules implemented, football-related fatalities andinjuries such as concussion continue to occur.

CONCLUSION

The establishment and implementation of rules and guide-lines governing tackling techniques has certainly played apivotal role in football safety. Also proved important are the

FIGURE 6. Photograph of NOCSAEhelmet safety and warning labels.

FIGURE 7. Photograph of Bike Athletic Pro-Edition helmet.

FIGURE 8. Illustration of Riddell VSR-4 helmet.

LEVY ET AL.


advent and evolution of the football helmet. Surely, much ofthe decline in head injury may be attributed to safer helmetdesign as a result of NOCSAE standards. However, somecritique the NOCSAE setup because, although the arrange-ment does a good job at assessing impacts under linear accel-eration, in reality, very few impacts occur under straightfor-ward linear impaction upon a static flat surface. Instead, amore complicated interaction occurs between two players,each with his own angular acceleration. These collisions arenow being studied in more depth with complex video editingtechniques, at various speeds, and from varying angles.

Competition between leading manufacturers has helped stircreative development of safer yet lighter-weight helmets.More advanced analytical and modeling techniques will con-tinue to further mold the evolution. Certainly, even the mostcurrent testing standards will have to evolve as well to satisfycritics that a linear drop model is simply insufficient to ade-quately assess safety in helmet design.

REFERENCES

1. Bennett T (ed): The NFLs Official Encyclopedic History of Professional Football.New York, Macmillan, 1977, ed 2.

2. Bishop PJ, Norman RW, Kozey JW: An evaluation of football helmets underimpact conditions. Am J Sports Med 12:233236, 1984.

3. Clarke K: An epidemiological view of the problem, in Torg JS (ed): AthleticInjuries to the Head, Neck, and Face. Philadelphia, Lea & Febiger, 1982.

4. Clarke K, Powell J: Football helmets and neurotrauma: An epidemiologicaloverview of three seasons. Med Sci Sports 11:138145, 1979.

5. Hodgson V: National Operating Committee on Standards for AthleticEquipment football helmet certification program. Med Sci Sports 7:225232,1975.

6. Llanos J, Pascoe D: The physiological strain and heat storage related tofootball helmets. Med Sci Sports Exerc 33:S223S227, 2001.

7. Myers T, Yoganadan N, Sances A Jr, Pintar F, Reinartz J, Battocletti J: Energyabsorption characteristics of football helmets under low and high rates ofloading. Biomed Mater Eng 3:1524, 1993.

8. National Operating Committee on Standards for Athletic Equipment: Stan-dard Drop Test Method and Equipment Used in Evaluating the PerformanceCharacteristics of Protective Headgear (NOCSAE Doc (ND) 001-04m04).Shawnee Mission, 2004.

9. Schneider RC: Football head and neck injury. Surg Neurol 27:507508, 1987.10. Thompson N, Halpern B, Curl W, Andrews J, Hunter S, Boring J: High

school football injuries: Evaluation. Am J Sports Med 15:117124, 1987.11. Torg JS, Quedenfeld T, Burstein A, Spealman A, Nichols CI: The National

Football Head and Neck Injury Registry: Report on cervical quadriplegia,19711975. Am J Sports Med 7:127132, 1979.

COMMENTS

The authors have reviewed the evolution of the footballhelmet and head protection in football from 1896 to thepresent. They have illustrated the article with the NationalOperating Committee on Standards for Athletic Equipmenthelmet testing system and illustrated the initial leather hel-mets with no internal suspension systems and the develop-ment to the present polycarbonate external shell with thevarious foam and air suspension systems that have evolvedover the years. The article is of significant historical interestand, with the recent introduction of the Revolution Helmet byRiddell and the Pro-Edition Helmet from Bike Athletic, bringsus to the current state of different helmet designs in use.

The authors are correct in their statement that competitionamong leading helmet manufacturers has benefited the ulti-mate goal of injury prevention. Not stated, however, is that,because of the medicolegal environment and the liability as-sociated with head and neck injuries in sports, many manu-facturers have been forced out of business, thus limiting theproviders to currently only three. I certainly agree with theauthors that the standards of the National Operating Commit-tee on Standards for Athletic Equipment do an adequate job inassessing impacts under linear acceleration, but the variousarticles published by Pellman et al. in this journal (but notreferenced in this article) do indeed support more advancedanalytical and modeling techniques for assessing head-protective devices in the future.

Joseph C. MaroonPittsburgh, Pennsylvania

Levy et al. describe the stages of head protection in the gameof American football. From the 19th-century leather hel-mets to todays advanced design, it is curious and amazing toimagine how the sports leaders sequentially added a firmerouter surface, an evolving face mask, chin strap, suspensionsystem, air bladder, and other modern features, while simul-taneously the impacts were becoming more violent.

In a sport in which the head protection must withstandrepeated impacts and yet continue to perform, there are sev-eral nuances for optimal function. The football helmet mustreduce the probability of impact-induced traumatic brain in-jury and at the same time be affordable, comfortable, andesthetically acceptable. In addition to the multitude of engi-neering and materials issues with which the sports helmetindustry has had to contend, they now are under assault from

FIGURE 9. Illustration of Riddell Revolution helmet.



the product liability standpoint. There have been many mile-stones in the development to our current technology, butimprovements in materials, design, and impact performanceassessments have all contributed to create todays helmets. Itis hoped that new synthetic components, mathematical andcomputer modeling, and research into the biomechanics of

football-related concussion will continue to improve uponhead protection in contact sports in the future. This is a finereview of the development of the modern football helmet.

Julian E. BailesMorgantown, West Virginia

Anatomic plate from Raymundi Vieussens Nevrographia Universalis. (See page 648 for the frontispiece tothe book.)

LEVY ET AL.


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