American football remains one of the most popular sports for young athletes. The injuries sustained during football, especially those to the head and neck, have been a topic of intense interest recently in both the public media and medical literature. The recognition of these injuries and the potential for long-term sequelae have led some physicians to call for a reduction in the number of contact practices, a postponement of tackling until a certain age, and even a ban on high school football. This statement reviews the literature regarding injuries in football, particularly those of the head and neck, the relationship between tackling and football-related injuries, and the potential effects of limiting or delaying tackling on injury risk.

With more than 1.1 million players, American football remains one of the most popular sports for male high school athletes.1 In addition, there are approximately 250 000 youth football players 5 to 15 years of age in Pop Warner leagues alone, making football one of the most popular sports for younger athletes as well.2 The injuries sustained during football, especially those to the head and neck, have been a topic of intense interest recently in both the public media and the medical literature. Concerns about the number of head and neck injuries, especially concussions and catastrophic injuries, have led some athletes to stop playing football.3 More recently, the cumulative effects of concussions and the potential for a cumulative effect of subconcussive blows to the head, defined as those that do not cause symptoms of concussion, have been hypothesized as a causative risk factor for chronic traumatic encephalopathy (CTE). The recognition of these injuries and the potential for long-term sequelae have led some physicians to call for a reduction in the number of contact practices, a postponement of tackling until a certain age, and even a ban on high school football.4,6 

Others, however, have argued that football is a generally safe sport that carries with it the substantial benefits of regular exercise on health7,8 as well as social and academic outcomes9,11 that outweigh the risks involved, pointing out that the risk of catastrophic injury is low, that most concussions resolve within a few days or weeks, and that there are substantial limitations to the current understanding of CTE. Some have expressed concerns about limiting contact practices or delaying the age at which tackling is introduced for fear that inadequate training may lead to unintended consequences once contact is allowed, such as increased forces of impact and more concussions.

The purpose of this statement is to review the literature regarding injuries in football, particularly those of the head and neck, the relationship between tackling and football-related injuries, and the potential effects of limiting or delaying tackling on injury risk. For purposes of this statement, unless otherwise defined, an athletic exposure (AE) refers to 1 athlete participating in 1 game or 1 practice.

The most commonly injured body parts in football at all ages are the knee,12,20 ankle,12,21 hand,21 and back.12,16 The head and neck sustain a relatively small proportion of overall injuries, ranging from 5% to 13%.12,18 Fortunately, most injuries are contusions, musculotendinous strains, and ligamentous sprains.12,13,15,17,18 

Available data suggest that both the overall incidence and the severity of injuries sustained by younger football players are lower than those sustained by older players,12,16,18,19,21,25 although this finding is not universally consistent.21 Some studies suggest that the incidence of overall injuries in football is similar to other sports,19,21 although the incidence of serious injuries appears to be greater for football than many other team sports.21,26 Although data regarding the most common injuries sustained by football players at the professional, collegiate, and high school level are more readily available, data regarding younger players is limited. The overall incidence of injury varies between studies, depending on how an injury was defined and how data were gathered (Table 1).

Although the risk of catastrophic injuries to the head and neck in football is low, with yearly estimates between 0.19 and 1.78 for every 100 000 participants,27,29 it appears higher in football than most other team sports.28 The risk of catastrophic injury during participation in football is, however, comparable to the risk in gymnastics and lower than the risk in ice hockey.28 The risk appears lower for youth players than for high school players and lower for high school players than for college players.27,29 The annual risk of quadriplegia is approximately 0.52 per 100 000 football participants and, again, appears lower for high school football players (0.50/100 000 participants) than collegiate players (0.82/100 000 participants). Spear tackling, or leading with the crown of the helmeted head while tackling by defensive players, continues to be the predominant mechanism of injury causing quadriplegia.29 

The cumulative effects of concussion have been documented both in athletes and those outside the realm of organized sports.30,34 Some former athletes who participated in sports that involve purposeful collisions and repetitive blows to the head have suffered from mood disorders, behavior problems, cognitive difficulties, gait abnormalities, headaches, and Parkinsonism later in life. At autopsy, these athletes had pathologic changes to the brain, including ventriculomegaly, cerebral atrophy, β-amyloid deposits, and phosphorylated τ deposits, an entity now commonly known as CTE.35,49 These case reports and case series have led to the hypothesis that repetitive blows to the head, whether concussive or subconcussive, result in the pathologic changes noted above and that these pathologic changes are associated with certain neurobehavioral characteristics. Whether the pathologic findings are solely attributable to the blows to the head and whether the pathologic changes are significantly associated with the neurobehavioral correlates is debated because these hypotheses remain to be tested by case-control and cohort studies.50,54 Some have argued that these effects may be attributable to confounding variables, such the use of drugs, alcohol, or performance-enhancing substances. It should be noted, however, that animal models of repetitive concussive brain injury have shown a decrease in cognitive function in the absence of such potential confounding variables.55,57 

“Second impact syndrome” is a term used to describe a devastating brain injury associated with cerebral edema that occurs after an often minor blow to the head is sustained before full recovery from a concussion.58,61 Although second impact syndrome is often associated with football, it has been observed in other sports, such as ice hockey, boxing, and skiing.58 Nearly all athletes with this diagnosis in the literature are younger than 20 years old. Given the rarity of this injury, its incidence in football is unknown. Furthermore, whether second impact syndrome is a unique entity, as opposed to cerebral edema attributable to a solitary blow to the head, remains debated.62,65 

Injuries are common during contact and tackling in particular.14,16,18 A higher proportion of injuries result from contact than noncontact mechanisms.14,16,17,23,66 Tackling, specifically, is the most common player activity at the time of injury20 and at the time of severe injury.26 Being tackled and tackling account for about half of high school and college football-related injuries.17,18 The majority of concussions result from tackling or being tackled.17 Head-to-head contact is one of the leading causes of concussions sustained by youth football players.18,23 

Badgeley et al studied the mechanisms leading to injury in a cohort of high school students playing football.17 Players in the older division had higher overall rates of injury than players in younger divisions. The leading mechanism of injury was player-to-player contact, with tackling/being tackled accounting for nearly half (46.2%) of all injuries. Similar findings have been reported in studies of youth football. In an observational cohort study of 208 Pop Warner football teams from New England, Goldberg et al reported on injuries sustained by players between the ages of 5 and 15 years that required restricted participation for more than 1 week.16 The vast majority (88%) of injuries occurred during contact with another player; 41% resulted directly from tackling. Players in the older division (Bantam) had higher overall rates of injury than players in younger divisions.

In a community survey by Radelet et al, the incidence of injuries sustained by children ages 7 to 13 years playing football (0.15 per 1000 AEs) was similar to, and in fact slightly lower than, that of baseball (0.17 per 1000 AEs) and boys’ soccer (0.17 per 1000 AEs).21 This finding was unexpected, but the authors noted that the results may have been affected by underreporting and differences in the interpretation of the definition of injury. The percentage of injuries that were defined as serious (fractures, dislocations, and concussions) was higher in football (13%) than other sports (0%–3%). Furthermore, the frequency of injury per team per season was 5 to 7 times higher in football than in baseball, soccer, or softball. The most common method of injury was contact with another player, although the authors did not report the nature of contact; therefore, the proportion of injuries attributable to tackling as opposed to blocking or incidental person-to-person contact is unknown. As with many other studies,17,18,67 their results showed a higher rate of injuries during football games (0.43 per 1000 AEs) than practices (0.07 per 1000 AEs).21 

The study by Badgeley et al suggests that during high school football, the majority (64.3%) of concussions occur when an athlete is tackling or being tackled,17 a finding consistent with previous work performed by some of the same investigators showing that tackling/being tackled accounted for half of all high school football injuries.18 During football played by younger athletes, Kontos et al showed that head-to-head contact was the most common mechanism of concussion, but whether head-to-head contact occurred during tackling, as opposed to blocking or incidental contact, is not discussed.23 

In a study of 42 varsity high school football players, Broglio et al used accelerometers to record head impacts resulting >14.4 g of linear acceleration and found a mean of 774 impacts per player during a single season. The mean number of impacts varied by player position, with linemen sustaining a higher number of impacts. Games were associated with a higher incidence of impacts than practices. Contact practices were associated with a higher incidence of impacts than noncontact practices.68 

In a single-season study of 7 football players aged 7 and 8 years, Daniel et al used accelerometers to record the cumulative number of impacts to the head.69 The authors examined both linear acceleration and rotational acceleration with blows to the front, side, rear, and top of the head. The average number of impacts per player was 107, with more impacts occurring during practices (59% of recorded impacts) than games (41% of recorded impacts). A greater number of high-force impacts (>95th percentile for acceleration) occurred during practices than games. The number of impacts experienced by these youth players was lower than that reported for high school and college players and more heavily weighted toward lower levels of impact. As might be expected, the number of impacts increased with increasing level of play, likely because of the increased size and strength of older players. The authors argued that restructuring practices might lead to a lower number of head impacts.69 This study was limited by a small sample size.

Fortunately, most neck injuries that occur during football are strains, sprains, and contusions.12,15 Cervical spine fractures and spinal cord injuries do occur, however, and some lead to permanent neurologic damage.15,16 

Although the rates of catastrophic injury in football are low, most of the cases that occur are sustained during tackling.29,70,73 Most cases of quadriplegia occur while the injured player is making a tackle.29 A majority of brain and cervical spine injury–related fatalities result from tackling or being tackled.67,74,75 

Brain injury–related fatalities account for approximately 69% of all football fatalities.67 Subdural hemorrhages are the most common injury associated with brain injury–related fatalities; tackling and being tackled67,74,76 are the most frequent activities when subdural hemorrhages occur.67 The annual incidence of catastrophic head injuries sustained by football players appears higher for high school athletes than college players (0.67 vs 0.21 per 100 000 participants).29 The majority are sustained by an athlete who is tackling or being tackled.29 

Football players are among the team sport athletes at highest risk for catastrophic cervical spine injuries.71 The annual incidence of catastrophic cervical spine injuries appears higher for collegiate players than for high school players (4.72 vs 1.10 per 100 000 participants).77 Most catastrophic cervical spine injuries occur during tackling, often when improper technique is used. Specifically, most spinal cord injuries are caused by axial loading of the cervical spine during head-down contact, often as a result of “spear tackling,” a method in which the athlete lowers his head, thereby lining up the vertebral bodies, and uses his body as a battering ram to deliver a blow to another player with the crown of his head.19,70,72,73 Fortunately, the incidence of catastrophic cervical spine injuries decreased after the banning of spear tackling in 1976.71,72 Catastrophic spine injuries still occur, however, and spear tackling remains a problem despite the ban.19,29,70,73 

Given the association of player-to-player contact with incidence of injury, decreasing the number of contact practices has been proposed as a method of decreasing injury risk, particularly concussions. Although the incidence of concussion is lower during practice than it is during games, there are far more practices than games. Because most impacts to the head occur during practices, decreasing the number of contact practices has been shown to decrease the overall number of head impacts that occur during the course of a season, thereby reducing the risk of any potential cumulative effects of such exposures.23,68,69,78 Some argue this may also lead to a decrease in the number of concussions.79 

Other authors, however, note that the risk of concussion is higher during games than it is during practices and argue that decreasing the number of contact practices is unlikely to reduce the number of concussions. In fact, they propose that the decrease in time spent practicing proper tackling technique may lead to an increase in the magnitude of impacts during games and an increase in the risk of concussion.23,68 Therefore, some authors have suggested that if contact practices are to be reduced as a means of decreasing overall head impact exposures, then extra emphasis should be placed on teaching appropriate tackling technique to avoid an increased risk during games.68 Other authors have also cautioned that a lack of proper training may increase risk of injury.18,24 

In a study of high school varsity football players, Broglio et al reported that limiting the number of contact practices to 1 per week would result in an 18% decrease in the number of impacts, whereas eliminating contact practices entirely would result in a 39% decrease in the number of impacts.68 That same study showed that games resulted in both a significantly higher number of impacts than practices as well as higher magnitude impacts than practices. The authors cautioned that limiting contact practices may increase the risk of high-magnitude impacts and concussions that occur during game time, especially if additional efforts are not made to teach proper tackling and techniques for safely absorbing tackles.68 

As opposed to high school and collegiate players,68 preliminary evidence suggests younger players may sustain higher magnitude impacts during practices as opposed to games.69 Thus, for younger players, limiting full contact practices while simultaneously teaching fundamental skills required for proper tackling and properly absorbing tackles may reduce the overall exposure to head impacts and high magnitude impacts. If CTE proves to be the result of cumulative impacts to the head, including subconcussive impacts, then limiting contact practices should decrease the risk of CTE.68,69,80 

A recent report from the Institute of Medicine concluded that although the concept of limiting the number of head impacts is sound, setting a limit on number of impacts or the magnitude of impacts per week or per season is without scientific basis.81 

Some physicians have recently argued that because the brain is in a rapid period of development during youth, contact should be eliminated from football until a certain age.4,6 Others have argued, however, that eliminating contact at a young age would prevent young athletes from learning the skills required to tackle, absorb a tackle, and fall to the ground safely. Then, when contact is later introduced, athletes will be ill prepared and forced to learn these skills at an age where they are bigger, faster, stronger, more coordinated, and capable of delivering more forceful blows. Some have suggested that this might increase the risk of injury23 and have argued the correct contact techniques should be taught at the earliest organized level.72,81 A previous study of high school football players in Wisconsin suggested that previous tackling experience is not independently associated with the risk of sustaining a sport-related concussion.82 Further investigation into the effects of delaying the introduction of tackling until a certain age must be conducted before informed recommendations can be made.

Although there does not appear to be any study to date showing the effect of delaying the age at which tackling is introduced to football on risk of injury, data from other sports suggest that eliminating tackling would decrease the risk of certain injuries for athletes participating at ages for which tackling would be prohibited.83,84 In a study of Canadian youth ice hockey players, Emery et al showed that the risk of injury, severe injury, concussion, and severe concussion was higher in leagues that allowed body checking than in leagues that did not allow body checking,83 confirming previous work that had demonstrated an association between body checking and the incidence of concussion.85 In a follow-up study, however, the same investigators reported that, once exposed to body checking, players who were not introduced to body checking until a later age were at significantly higher risk of severe injuries than those exposed to body checking at an earlier age.86 The risk of sport-related concussion was also higher in those previously unexposed to body checking, although the findings were not statistically significant.86 Other studies of youth ice hockey players have shown no significant difference in the incidence of injury between those exposed to body checking at differing ages. However, a previous study by MacPherson et al showed that hockey players exposed to body checking at a younger age had a significantly higher odds of suffering a checking injury than those exposed to checking at a later age.85 

Initiating contact with the shoulder while the head is up is believed to be the safest way to tackle in football. Most experts recommend that proper technique be learned and practiced regularly as a means of reducing the risk of injury.17,18,71,72,79 A recent initiative by USA Football emphasizes keeping the head up during tackling to prevent catastrophic injuries as well as concussions, although this new coaching method needs further study.

In addition to changing practice regimens and teaching proper tackling techniques, some have proposed changes to the rules of football as a means of reducing head and neck injuries. Indeed, the 1976 banning of spear tackling has been widely credited with reducing the numbers of cervical spinal injuries resulting in quadriplegia.70,73,77,87,88 Unfortunately, spear tackling has persisted even since the 1976 rule change, and cervical spine injuries continue to occur.73,88,89 Modification and consistent enforcement of the rules may lead to a further decrease in the risk of injury, including catastrophic injuries.73,79,89 

The introduction of helmets to football and the updating of helmet design is widely credited for playing a role in the reduction of head injuries, particularly catastrophic head injuries and brain injury–related fatalities.67,90,91 Therefore, athletes participating in football should wear undamaged, properly fitted helmets with secured chin straps. By protecting the scalp from the discomfort of blows to the vertex of the head, however, helmets are considered, in part, to have led to an increase in the number of cases of quadriplegia by encouraging the use of the head as the point of impact.92 This trend was fortunately reduced by the banning of spear tackling, as noted previously. The role of helmets in preventing concussions is less clear. Although some studies suggest that helmet design might play a role in reducing the incidence of concussion,93,94 many experts refute such a claim.82,95,96 In a recent study of more than 2000 high school football players, McGuine et al reported that helmet model had no significant effect on the incidence of sport-related concussion.82 As of now, there is little reliable evidence that concussions can be prevented or mitigated by any of the currently available helmet designs.95,97 

Mouth guards are effective at reducing the incidence of dental injuries.97,98 Although some studies have suggested an effect of mouthguard type on the incidence of concussion,82,99,100 there are few reliable data suggesting that any currently available mouth guards are effective at preventing or reducing the incidence of concussion.95,96,101,103 

Although there is some evidence that neck rolls and cowboy collars can reduce movement of the head and neck, there is limited evidence regarding their effect on the incidence of burners or stingers, injuries to the nerve of the upper arm that result in a burning or stinging sensation.104,106 Because neck rolls limit extension of the neck, they may, theoretically, interfere with the ability of the proper head-up tackling technique.

Neck muscle strengthening has been recommended by the National Athletic Trainers’ Association as a means of decreasing neck fatigue, thereby allowing for maintenance of the head-up position associated with proper tackling technique and decreasing the risk of burners and stingers.72 Furthermore, weak neck musculature has been proposed as a risk factor for concussion.107,109 Acceleration of a struck object is inversely proportional to its mass. Because concussion results from a rotational acceleration of the brain, it has been suggested that increasing the effective mass of the head might result in a decreased acceleration of the brain after impact. The head becomes more firmly bonded to the rest of the body when the neck muscles are contracted, thereby increasing the effective mass of the head and decreasing the resultant acceleration after impact.109 This increase in effective mass is thought to explain the decreased risk of concussion when collisions are anticipated.108,109 Thus, by increasing cervical muscle strength, athletes might decrease their risk of concussion.108,110 Preliminary evidence supports this hypothesis.111 Other preliminary studies suggest that it may be cervical stiffness, as opposed to strength alone, that is associated with risk of injury.112 

Most injuries sustained during participation in youth football are minor, including injuries to the head and neck. The incidences of severe injuries, catastrophic injuries, and concussion, however, are higher in football than most other team sports and appear to increase with age. Player-to-player contact results in an increase in the number of subconcussive impacts that occur during football. Concussion is associated with player-to-player contact and tackling, in particular. Severe and catastrophic injuries, particularly those of the head and neck, are associated with tackling, often when improper and illegal technique, such as spear tackling, is used. Efforts should be made to improve the teaching of proper tackling technique and enforce existing rules prohibiting the use of improper technique.

  1. Officials and coaches must ensure proper enforcement of the rules of the game. A significant number of concussions and catastrophic injuries occur because of improper and illegal contact, such as spear tackling. There is a culture of tolerance of head first, illegal hits. This culture has to change to one that protects the head for both the tackler and those players being tackled. Stronger sanctions for contact to the head, especially of a defenseless player, should be considered, up to and including expulsion from the game. The culture should change to one of zero tolerance of illegal, head-first hits.

  2. Removing tackling from football altogether would likely lead to a decrease in the incidence of overall injuries, severe injuries, catastrophic injuries, and concussions. The American Academy of Pediatrics recognizes, however, that the removal of tackling from football would lead to a fundamental change in the way the game is played. Participants in football must decide whether the potential health risks of sustaining these injuries are outweighed by the recreational benefits associated with proper tackling.

  3. The expansion of nontackling leagues for young athletes who enjoy the game of football and want to be physically active but do not want to be exposed to the collisions currently associated with the game should be considered by football leagues and organizations. This would allow athletes to choose to participate in football without tackling and its associated risks, even after the age at which tackling is introduced.

  4. Although the effect of subconcussive blows on long-term cognitive function, incidence of CTE, and other health outcomes remains unclear, repetitive trauma to the head is of no clear benefit to the game of football or the health of football players. If subconcussive blows to the head result in negative long-term effects on health, then limiting impacts to the head should reduce the risk of these long-term health problems. Thus, efforts should be made by coaches and officials to reduce the number of impacts to the head that occur during participation in football. Further research is needed in this area.

  5. Delaying the age at which tackling is introduced to the game would likely decrease the risk of these injuries for the age levels at which tackling would be prohibited. Once tackling is introduced, however, athletes who have no previous experience with tackling would be exposed to collisions for the first time at an age at which speeds are faster, collision forces are greater, and injury risk is higher. Lack of experience with tackling and being tackled may lead to an increase in the number and severity of injuries once tackling is introduced. Therefore, if regulations that call for the delaying of tackling until a certain age are to be made, they must be accompanied by coaches offering instruction in proper tackling technique as well as the teaching of the skills necessary to evade tackles and absorb being tackled. It is unclear whether such techniques and the neuromuscular control necessary for performing them can be adequately learned in the absence of contact.

  6. Although definitive scientific evidence is lacking, strengthening of the cervical musculature will likely reduce the risk of concussions in football by limiting the acceleration of the head after impact. Physical therapists, athletic trainers, or strength and conditioning specialists, with expertise in the strengthening and conditioning of pediatric athletes, are best qualified to help young football players achieve the neck strength that will help prevent injuries.

  7. Given their importance in the medical management of sport-related injuries and preliminary evidence suggesting an association between athletic trainers presence and a decreased incidence of sport-related injuries,113 efforts should be made by football teams to have athletic trainers at the sidelines during organized football games and practices.

William P. Meehan, III, MD, FAAP

Gregory L. Landry, MD, FAAP

Joel S. Brenner, MD, MPH, FAAP, Chairperson

Cynthia R. LaBella, MD, FAAP, Chairperson-Elect

Margaret A. Brooks, MD, FAAP

Alex Diamond, DO, MPH, FAAP

Amanda K. Weiss Kelly, MD, FAAP

Michele LaBotz, MD, FAAP

Kelsey Logan, MD, MPH, FAAP

Keith J. Loud, MDCM, MSc, FAAP

Kody A. Moffatt, MD, FAAP

Blaise Nemeth, MD, MS, FAAP

Brooke Pengel, MD, FAAP

William Hennrikus, MD, FAAP

Rebecca Demorest, MD, FAAP

Andrew J. M. Gregory, MD, FAAP – American College of Sports Medicine

Mark Halstead, MD, FAAP – American Medical Society for Sports Medicine

Lisa K. Kluchurosky, MEd, ATC – National Athletic Trainers Association

Gregory Canty, MD, FAAP

Emily Hanson, ATC, CSCS

Neeru A. Jayanthi, MD

Anjie Emanuel, MPH

     
  • AE

    athletic exposure

  •  
  • CTE

    chronic traumatic encephalopathy

This document is copyrighted and is property of the American Academy of Pediatrics and its Board of Directors. All authors have filed conflict of interest statements with the American Academy of Pediatrics. Any conflicts have been resolved through a process approved by the Board of Directors. The American Academy of Pediatrics has neither solicited nor accepted any commercial involvement in the development of the content of this publication.

Policy statements from the American Academy of Pediatrics benefit from expertise and resources of liaisons and internal (AAP) and external reviewers. However, policy statements from the American Academy of Pediatrics may not reflect the views of the liaisons or the organizations or government agencies that they represent.

The guidance in this statement does not indicate an exclusive course of treatment or serve as a standard of medical care. Variations, taking into account individual circumstances, may be appropriate.

All policy statements from the American Academy of Pediatrics automatically expire 5 years after publication unless reaffirmed, revised, or retired at or before that time.

1
Frollo J. Football remains number 1 among high school participation. 2011. Available at: http://usafootball.com/news/coaches/football-remains-no-1-among-high-school-participation. Accessed March 14, 2014
2
Alves
WM
,
Rimel
RW
,
Nelson
WE
.
University of Virginia prospective study of football-induced minor head injury: status report.
Clin Sports Med
.
1987
;
6
(
1
):
211
218
[PubMed]
3
Fainaru S, Fainaru-Wada M. Youth football participation drops. November 14, 2013. Available at: http://espn.go.com/espn/otl/story/_/page/popwarner/pop-warner-youth-football-participation-drops-nfl-concussion-crisis-seen-causal-factor
4
Cantu
RC
.
Concussions and Our Kids: America’s Leading Expert on How to Protect Young Athletes and Keep Sports Safe
.
Boston, MA
:
Houghton Mifflin
;
2012
5
Harris D. High school football ban proposal under attack in New Hampshire. 2012. Available at: http://abcnews.go.com/US/high-school-football-ban-proposal-attack-hampshire/story?id=17559475. Accessed March 14, 2014
6
Robbins L. Let’s ban tackle football under age 18. Real Clear Sports. December 6, 2012. Available at: http://www.realclearsports.com/articles/2012/12/06/lets_ban_tackle_football_until_age_18_97818.html. Accessed September 4, 2015
7
Goldstein
LB
,
Whitsel
LP
,
Meltzer
N
, et al
American Heart Association (AHA) Advocacy Coordinating Committee
Council on Cardiovascular Nursing, AHA
Council on the Kidney in Cardiovascular Disease, AHA
Council on Cardiovascular Radiology and Intervention, AHA
Council on Cardiovascular Surgery and Anesthesia, AHA
Council on Clinical Cardiology, AHA
Council on Cardiovascular Disease in the Young, AHA
Council on Cardiopulmonary, Critical Care, Perioperative, and Resuscitation, AHA
Council on Peripheral Vascular Disease, AHA
Council on Arteriosclerosis, Thrombosis and Vascular Biology, AHA
Council on Epidemiology and Prevention, AHA
Council on Nutrition, Physical Activity and Metabolism, AHA
Interdisciplinary Council on Functional Genomics and Translational Biology, AHA
.
American Heart Association and nonprofit advocacy: past, present, and future. A policy recommendation from the American Heart Association.
Circulation
.
2011
;
123
(
7
):
816
832
[PubMed]
8
Haskell
WL
,
Lee
IM
,
Pate
RR
, et al
.
Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association.
Med Sci Sports Exerc
.
2007
;
39
(
8
):
1423
1434
[PubMed]
9
Bjorklund
DF
,
Brown
RD
.
Physical play and cognitive development: integrating activity, cognition, and education.
Child Dev
.
1998
;
69
(
3
):
604
606
[PubMed]
10
Chomitz
VR
,
Slining
MM
,
McGowan
RJ
,
Mitchell
SE
,
Dawson
GF
,
Hacker
KA
.
Is there a relationship between physical fitness and academic achievement? Positive results from public school children in the northeastern United States.
J Sch Health
.
2009
;
79
(
1
):
30
37
[PubMed]
11
Donnelly
JE
,
Lambourne
K
.
Classroom-based physical activity, cognition, and academic achievement.
Prev Med
.
2011
;
52
(
suppl 1
):
S36
S42
[PubMed]
12
Adickes
MS
,
Stuart
MJ
.
Youth football injuries.
Sports Med
.
2004
;
34
(
3
):
201
207
[PubMed]
13
Stuart
MJ
,
Morrey
MA
,
Smith
AM
,
Meis
JK
,
Ortiguera
CJ
.
Injuries in youth football: a prospective observational cohort analysis among players aged 9 to 13 years.
Mayo Clin Proc
.
2002
;
77
(
4
):
317
322
[PubMed]
14
Turbeville
SD
,
Cowan
LD
,
Asal
NR
,
Owen
WL
,
Anderson
MA
.
Risk factors for injury in middle school football players.
Am J Sports Med
.
2003
;
31
(
2
):
276
281
[PubMed]
15
Dompier
TP
,
Powell
JW
,
Barron
MJ
,
Moore
MT
.
Time-loss and non-time-loss injuries in youth football players.
J Athl Train
.
2007
;
42
(
3
):
395
402
[PubMed]
16
Goldberg
B
,
Rosenthal
PP
,
Robertson
LS
,
Nicholas
JA
.
Injuries in youth football.
Pediatrics
.
1988
;
81
(
2
):
255
261
[PubMed]
17
Badgeley
MA
,
McIlvain
NM
,
Yard
EE
,
Fields
SK
,
Comstock
RD
.
Epidemiology of 10,000 high school football injuries: patterns of injury by position played.
J Phys Act Health
.
2013
;
10
(
2
):
160
169
[PubMed]
18
Shankar
PR
,
Fields
SK
,
Collins
CL
,
Dick
RW
,
Comstock
RD
.
Epidemiology of high school and collegiate football injuries in the United States, 2005–2006.
Am J Sports Med
.
2007
;
35
(
8
):
1295
1303
[PubMed]
19
Demorest
RA
,
Landry
GL
.
Prevention of pediatric sports injuries.
Curr Sports Med Rep
.
2003
;
2
(
6
):
337
343
[PubMed]
20
Knowles
SB
,
Marshall
SW
,
Bowling
MJ
, et al
.
Risk factors for injury among high school football players.
Epidemiology
.
2009
;
20
(
2
):
302
310
[PubMed]
21
Radelet
MA
,
Lephart
SM
,
Rubinstein
EN
,
Myers
JB
.
Survey of the injury rate for children in community sports.
Pediatrics
.
2002
;
110
(
3
). Available at: www.pediatrics.org/cgi/content/full/110/3/e28
[PubMed]
22
Malina RM, Morano PJ, Barron M, Miller SJ, Cumming SP, Kontos AP. Incidence and player risk factors for injury in youth football. Clin J Sport Med. 2006;16:214–222
23
Kontos
AP
,
Elbin
RJ
,
Fazio-Sumrock
VC
, et al
.
Incidence of sports-related concussion among youth football players aged 8–12 years.
J Pediatr
.
2013
;
163
(
3
):
717
720
[PubMed]
24
Linder MM, Townsend DJ, Jones JC, Balkcom IL, Anthony CR. Incidence of adolescent injuries in junior high school football and its relationship to sexual maturity. Clin J Sport Med. 1995;5(3):167–170
25
Damore
DT
,
Metzl
JD
,
Ramundo
M
,
Pan
S
,
Van Amerongen
R
.
Patterns in childhood sports injury.
Pediatr Emerg Care
.
2003
;
19
(
2
):
65
67
[PubMed]
26
Darrow
CJ
,
Collins
CL
,
Yard
EE
,
Comstock
RD
.
Epidemiology of severe injuries among United States high school athletes: 2005–2007.
Am J Sports Med
.
2009
;
37
(
9
):
1798
1805
[PubMed]
27
Mueller FO, Cantu RC. Annual survey of catastrophic football injuries 1977–2011. Available at: http://www.unc.edu/depts/nccsi/FBCATReport2011.pdf. Accessed March 7, 2014
28
Zemper
ED
.
Catastrophic injuries among young athletes.
Br J Sports Med
.
2010
;
44
(
1
):
13
20
[PubMed]
29
Boden
BP
,
Tacchetti
RL
,
Cantu
RC
,
Knowles
SB
,
Mueller
FO
.
Catastrophic head injuries in high school and college football players.
Am J Sports Med
.
2007
;
35
(
7
):
1075
1081
[PubMed]
30
Collins MW, Lovell MR, Iverson GL, Cantu RC, Maroon JC, Field M. Cumulative effects of concussion in high school athletes. Neurosurgery. 2002;51(5):1175–1179; discussion 1180–1171
31
Gronwall
D
,
Wrightson
P
.
Cumulative effect of concussion.
Lancet
.
1975
;
2
(
7943
):
995
997
[PubMed]
32
Guskiewicz
KM
,
McCrea
M
,
Marshall
SW
, et al
.
Cumulative effects associated with recurrent concussion in collegiate football players: the NCAA Concussion Study.
JAMA
.
2003
;
290
(
19
):
2549
2555
[PubMed]
33
Iverson
GL
,
Gaetz
M
,
Lovell
MR
,
Collins
MW
.
Cumulative effects of concussion in amateur athletes.
Brain Inj
.
2004
;
18
(
5
):
433
443
[PubMed]
34
Eisenberg
MA
,
Andrea
J
,
Meehan
W
,
Mannix
R
.
Time interval between concussions and symptom duration.
Pediatrics
.
2013
;
132
(
1
):
8
17
[PubMed]
35
Corsellis
JA
,
Bruton
CJ
,
Freeman-Browne
D
.
The aftermath of boxing.
Psychol Med
.
1973
;
3
(
3
):
270
303
[PubMed]
36
Critchley
M
.
Medical aspects of boxing, particularly from a neurological standpoint.
BMJ
.
1957
;
1
(
5015
):
357
362
[PubMed]
37
Jordan
BD
.
Chronic traumatic brain injury associated with boxing.
Semin Neurol
.
2000
;
20
(
2
):
179
185
[PubMed]
38
Jordan
BD
,
Matser
EJ
,
Zimmerman
RD
,
Zazula
T
.
Sparring and cognitive function in professional boxers.
Phys Sportsmed
.
1996
;
24
(
5
):
87
98
[PubMed]
39
Jordan
BD
,
Relkin
NR
,
Ravdin
LD
,
Jacobs
AR
,
Bennett
A
,
Gandy
S
.
Apolipoprotein E epsilon4 associated with chronic traumatic brain injury in boxing.
JAMA
.
1997
;
278
(
2
):
136
140
[PubMed]
40
McKee
AC
,
Cantu
RC
,
Nowinski
CJ
, et al
.
Chronic traumatic encephalopathy in athletes: progressive tauopathy after repetitive head injury.
J Neuropathol Exp Neurol
.
2009
;
68
(
7
):
709
735
[PubMed]
41
McKee
AC
,
Gavett
BE
,
Stern
RA
, et al
.
TDP-43 proteinopathy and motor neuron disease in chronic traumatic encephalopathy.
J Neuropathol Exp Neurol
.
2010
;
69
(
9
):
918
929
[PubMed]
42
McKee AC, Stein TD, Nowinski CJ, et al. The spectrum of disease in chronic traumatic encephalopathy. Brain. 2013;136(pt 1):43–64
43
Omalu
B
,
Bailes
J
,
Hamilton
RL
, et al
.
Emerging histomorphologic phenotypes of chronic traumatic encephalopathy in American athletes.
Neurosurgery
.
2011
;
69
(
1
):
173
183, discussion 183
[PubMed]
44
Omalu
B
,
Hammers
JL
,
Bailes
J
, et al
.
Chronic traumatic encephalopathy in an Iraqi war veteran with posttraumatic stress disorder who committed suicide.
Neurosurg Focus
.
2011
;
31
(
5
):
E3
[PubMed]
45
Omalu
BI
,
Bailes
J
,
Hammers
JL
,
Fitzsimmons
RP
.
Chronic traumatic encephalopathy, suicides and parasuicides in professional American athletes: the role of the forensic pathologist.
Am J Forensic Med Pathol
.
2010
;
31
(
2
):
130
132
[PubMed]
46
Omalu BI, DeKosky ST, Hamilton RL, et al. Chronic traumatic encephalopathy in a national football league player: part II. Neurosurgery. 2006;59(5):1086–1092; discussion 1092–1083
47
Omalu
BI
,
DeKosky
ST
,
Minster
RL
,
Kamboh
MI
,
Hamilton
RL
,
Wecht
CH
.
Chronic traumatic encephalopathy in a National Football League player.
Neurosurgery
.
2005
;
57
(
1
):
128
134, discussion 128–134
[PubMed]
48
Roberts
GW
,
Allsop
D
,
Bruton
C
.
The occult aftermath of boxing.
J Neurol Neurosurg Psychiatry
.
1990
;
53
(
5
):
373
378
[PubMed]
49
Tokuda
T
,
Ikeda
S
,
Yanagisawa
N
,
Ihara
Y
,
Glenner
GG
.
Re-examination of ex-boxers’ brains using immunohistochemistry with antibodies to amyloid beta-protein and tau protein.
Acta Neuropathol
.
1991
;
82
(
4
):
280
285
[PubMed]
50
Randolph
C
.
Is chronic traumatic encephalopathy a real disease?
Curr Sports Med Rep
.
2014
;
13
(
1
):
33
37
[PubMed]
51
Wortzel HS, Shura RD, Brenner LA. Chronic traumatic encephalopathy and suicide: a systematic review. BioMed Res Int. 2013;2013:424280
52
Tator
CH
.
Chronic traumatic encephalopathy: how serious a sports problem is it?
Br J Sports Med
.
2014
;
48
(
2
):
81
83
[PubMed]
53
Iverson
GL
.
Chronic traumatic encephalopathy and risk of suicide in former athletes.
Br J Sports Med
.
2014
;
48
(
2
):
162
165
[PubMed]
54
Gardner
A
,
Iverson
GL
,
McCrory
P
.
Chronic traumatic encephalopathy in sport: a systematic review.
Br J Sports Med
.
2014
;
48
(
2
):
84
90
[PubMed]
55
Mannix
RM
, Meehan
WP III, Mandeville J, et al. Clinical correlates in an experimental model of repetitive mild brain injury.
Ann Neurol
.
2013;74(1):65–75
56
DeFord
SM
,
Wilson
MS
,
Rice
AC
, et al
.
Repeated mild brain injuries result in cognitive impairment in B6C3F1 mice.
J Neurotrauma
.
2002
;
19
(
4
):
427
438
[PubMed]
57
Meehan
WP
 III
,
Zhang
J
,
Mannix
R
,
Whalen
MJ
.
Increasing recovery time between injuries improves cognitive outcome after repetitive mild concussive brain injuries in mice.
Neurosurgery
.
2012
;
71
(
4
):
885
891
[PubMed]
58
Cantu
RC
.
Second impact syndrome: a risk in any contact sport.
Phys Sportsmed
.
1995
;
23
(
6
):27–34
59
Cantu
RC
.
Second-impact syndrome.
Clin Sports Med
.
1998
;
17
(
1
):
37
44
[PubMed]
60
Cantu
RC
,
Gean
AD
.
Second-impact syndrome and a small subdural hematoma: an uncommon catastrophic result of repetitive head injury with a characteristic imaging appearance.
J Neurotrauma
.
2010
;
27
(
9
):
1557
1564
[PubMed]
61
Saunders
RL
,
Harbaugh
RE
.
The second impact in catastrophic contact-sports head trauma.
JAMA
.
1984
;
252
(
4
):
538
539
[PubMed]
62
McCrory P. Does second impact syndrome exist? Clin J Sport Med. 2001;11(3):144–149
63
McCrory
P
,
Davis
G
,
Makdissi
M
.
Second impact syndrome or cerebral swelling after sporting head injury.
Curr Sports Med Rep
.
2012
;
11
(
1
):
21
23
[PubMed]
64
McCrory
PR
,
Berkovic
SF
.
Second impact syndrome.
Neurology
.
1998
;
50
(
3
):
677
683
[PubMed]
65
Wetjen
NM
,
Pichelmann
MA
,
Atkinson
JL
.
Second impact syndrome: concussion and second injury brain complications.
J Am Coll Surg
.
2010
;
211
(
4
):
553
557
[PubMed]
66
Zoch
TW
,
Cleveland
DA
,
McCormick
J
,
Toyama
K
,
Nordstrom
DL
.
Football injuries in a rural area.
Wis Med J
.
1996
;
95
(
8
):
570
573
[PubMed]
67
Cantu RC, Mueller FO. Brain injury-related fatalities in American football, 1945-1999. Neurosurgery. 2003;52(4):846–852; discussion 852–843
68
Broglio
SP
,
Martini
D
,
Kasper
L
,
Eckner
JT
,
Kutcher
JS
.
Estimation of head impact exposure in high school football: implications for regulating contact practices.
Am J Sports Med
.
2013
;
41
(
12
):
2877
2884
[PubMed]
69
Daniel
RW
,
Rowson
S
,
Duma
SM
.
Head impact exposure in youth football.
Ann Biomed Eng
.
2012
;
40
(
4
):
976
981
[PubMed]
70
Banerjee
R
,
Palumbo
MA
,
Fadale
PD
.
Catastrophic cervical spine injuries in the collision sport athlete, part 1: epidemiology, functional anatomy, and diagnosis.
Am J Sports Med
.
2004
;
32
(
4
):
1077
1087
[PubMed]
71
Erlanger
D
,
Kaushik
T
,
Cantu
R
, et al
.
Symptom-based assessment of the severity of a concussion.
J Neurosurg
.
2003
;
98
(
3
):
477
484
[PubMed]
72
Heck
JF
,
Clarke
KS
,
Peterson
TR
,
Torg
JS
,
Weis
MP
.
National Athletic Trainers’ Association Position Statement: head-down contact and spearing in tackle football.
J Athl Train
.
2004
;
39
(
1
):
101
111
[PubMed]
73
Rihn
JA
,
Anderson
DT
,
Lamb
K
, et al
.
Cervical spine injuries in American football.
Sports Med
.
2009
;
39
(
9
):
697
708
[PubMed]
74
Mueller
FO
.
Fatalities from head and cervical spine injuries occurring in tackle football: 50 years’ experience.
Clin Sports Med
.
1998
;
17
(
1
):
169
182
[PubMed]
75
Mueller
FO
,
Blyth
CS
.
Fatalities from head and cervical spine injuries occurring in tackle football: 40 years’ experience.
Clin Sports Med
.
1987
;
6
(
1
):
185
196
[PubMed]
76
Forbes JA, Zuckerman S, Abla AA, Mocco J, Bode K, Eads T. Biomechanics of subdural hemorrhage in American football: review of the literature in response to rise in incidence. Childs Nerv Syst. 2014;30(2):197–203
77
Boden
BP
,
Tacchetti
RL
,
Cantu
RC
,
Knowles
SB
,
Mueller
FO
.
Catastrophic cervical spine injuries in high school and college football players.
Am J Sports Med
.
2006
;
34
(
8
):
1223
1232
[PubMed]
78
Cobb
BR
,
Urban
JE
,
Davenport
EM
, et al
.
Head impact exposure in youth football: elementary school ages 9–12 years and the effect of practice structure.
Ann Biomed Eng
.
2013
;
41
(
12
):
2463
2473
[PubMed]
79
Harmon
KG
,
Drezner
JA
,
Gammons
M
, et al
.
American Medical Society for Sports Medicine position statement: concussion in sport.
Br J Sports Med
.
2013
;
47
(
1
):
15
26
[PubMed]
80
Wong
RH
,
Wong
AK
,
Bailes
JE
.
Frequency, magnitude, and distribution of head impacts in Pop Warner football: the cumulative burden.
Clin Neurol Neurosurg
.
2014
;
118
:
1
4
[PubMed]
81
Graham RRF, Ford MA, Spicer CM. Sports-Related Concussions in Youth: Improving the Science, Changing the Culture. Washington, DC: Institute of Medicine and National Research Council of the National Academies; 2014
82
McGuine
TA
,
Hetzel
S
,
McCrea
M
,
Brooks
MA
.
Protective equipment and player characteristics associated with the incidence of sport-related concussion in high school football players: a multifactorial prospective study.
Am J Sports Med
.
2014
;
42
(
10
):
2470
2478
[PubMed]
83
Emery
CA
,
Kang
J
,
Shrier
I
, et al
.
Risk of injury associated with body checking among youth ice hockey players.
JAMA
.
2010
;
303
(
22
):
2265
2272
[PubMed]
84
Brooks
A
,
Loud
KJ
,
Brenner
JS
, et al
Council on Sports Medicine and Fitness
.
Reducing injury risk from body checking in boys’ youth ice hockey.
Pediatrics
.
2014
;
133
(
6
):
1151
1157
[PubMed]
85
Macpherson
A
,
Rothman
L
,
Howard
A
.
Body-checking rules and childhood injuries in ice hockey.
Pediatrics
.
2006
;
117
(
2
). Available at: www.pediatrics.org/cgi/content/full/117/2/e143
[PubMed]
86
Emery
CA
,
Kang
J
,
Schneider
KJ
,
Meeuwisse
WH
.
Risk of injury and concussion associated with team performance and penalty minutes in competitive youth ice hockey.
Br J Sports Med
.
2011
;
45
(
16
):
1289
1293
[PubMed]
87
Boden
BP
.
Direct catastrophic injury in sports.
J Am Acad Orthop Surg
.
2005
;
13
(
7
):
445
454
[PubMed]
88
Chao
S
,
Pacella
MJ
,
Torg
JS
.
The pathomechanics, pathophysiology and prevention of cervical spinal cord and brachial plexus injuries in athletics.
Sports Med
.
2010
;
40
(
1
):
59
75
[PubMed]
89
Heck
JF
.
The incidence of spearing during a high school’s 1975 and 1990 football seasons.
J Athl Train
.
1996
;
31
(
1
):
31
37
[PubMed]
90
Levy ML, Ozgur BM, Berry C, Aryan HE, Apuzzo ML. Birth and evolution of the football helmet. Neurosurgery. 2004;55(3):656–661; discussion 661–652
91
Levy
ML
,
Ozgur
BM
,
Berry
C
,
Aryan
HE
,
Apuzzo
ML
.
Analysis and evolution of head injury in football.
Neurosurgery
.
2004
;
55
(
3
):
649
655
[PubMed]
92
Torg
JS
,
Truex
R
 Jr
,
Quedenfeld
TC
,
Burstein
A
,
Spealman
A
,
Nichols
C
 III
.
The National Football Head and Neck Injury Registry. Report and conclusions 1978.
JAMA
.
1979
;
241
(
14
):
1477
1479
[PubMed]
93
Collins
M
,
Lovell
MR
,
Iverson
GL
,
Ide
T
,
Maroon
J
.
Examining concussion rates and return to play in high school football players wearing newer helmet technology: a three-year prospective cohort study.
Neurosurgery
.
2006
;
58
(
2
):
275
286, discussion 275–286
[PubMed]
94
Zemper
ED
.
Analysis of cerebral concussion frequency with the most commonly used models of football helmets.
J Athl Train
.
1994
;
29
(
1
):
44
50
[PubMed]
95
Benson
BW
,
Hamilton
GM
,
Meeuwisse
WH
,
McCrory
P
,
Dvorak
J
.
Is protective equipment useful in preventing concussion? A systematic review of the literature.
Br J Sports Med
.
2009
;
43
(
suppl 1
):
i56
i67
[PubMed]
96
McCrory
P
,
Meeuwisse
WH
,
Aubry
M
, et al
.
Consensus statement on concussion in sport: the 4th International Conference on Concussion in Sport held in Zurich, November 2012.
Br J Sports Med
.
2013
;
47
(
5
):
250
258
[PubMed]
97
Trojian
TH
,
Mohamed
N
.
Demystifying preventive equipment in the competitive athlete.
Curr Sports Med Rep
.
2012
;
11
(
6
):
304
308
[PubMed]
98
Newsome PR, Tran DC, Cooke MS. The role of the mouthguard in the prevention of sports-related dental injuries: a review. Int J Paediatr Dentistry. 2001;11(6):396–404
99
Winters
J
,
DeMont
R
.
Role of mouthguards in reducing mild traumatic brain injury/concussion incidence in high school football athletes.
Gen Dent
.
2014
;
62
(
3
):
34
38
[PubMed]
100
Singh GD, Maher GJ, Padilla RR. Customized mandibular orthotics in the prevention of concussion/mild traumatic brain injury in football players: a preliminary study. Dent Traumatol. 2009;25(5):515–521
101
Barbic D, Pater J, Brison RJ. Comparison of mouth guard designs and concussion prevention in contact sports: a multicenter randomized controlled trial. Clin J Sport Med. 2005;15(5):294–298
102
Wisniewski JF, Guskiewicz K, Trope M, Sigurdsson A. Incidence of cerebral concussions associated with type of mouthguard used in college football. Dent Traumatol. 2004;20(3):143–149
103
Mihalik JP, McCaffrey MA, Rivera EM, et al. Effectiveness of mouthguards in reducing neurocognitive deficits following sports-related cerebral concussion. Dent Traumatol. 2007;23(1):14–20
104
Gorden
JA
,
Straub
SJ
,
Swanik
CB
,
Swanik
KA
.
Effects of football collars on cervical hyperextension and lateral flexion.
J Athl Train
.
2003
;
38
(
3
):
209
215
[PubMed]
105
Rowson
S
,
McNeely
D
,
Duma
S
.
Lateral bending biomechanical analysis of neck protection devices used in football.
Biomed Sci Instrum
.
2007
;
43
:
200
205
[PubMed]
106
Rowson S, McNeely DE, Brolinson PG, Duma SM. Biomechanical analysis of football neck collars. Clin J Sport Med. 2008;18(4):316–321
107
Benson
BW
,
McIntosh
AS
,
Maddocks
D
,
Herring
SA
,
Raftery
M
,
Dvorák
J
.
What are the most effective risk-reduction strategies in sport concussion?
Br J Sports Med
.
2013
;
47
(
5
):
321
326
[PubMed]
108
Viano DC, Casson IR, Pellman EJ. Concussion in professional football: biomechanics of the struck player—part 14. Neurosurgery. 2007;61(2):313–327; discussion 327–318
109
Mihalik
JP
,
Blackburn
JT
,
Greenwald
RM
,
Cantu
RC
,
Marshall
SW
,
Guskiewicz
KM
.
Collision type and player anticipation affect head impact severity among youth ice hockey players.
Pediatrics
.
2010
;
125
(
6
). Available at: www.pediatrics.org/cgi/content/full/125/6/e1394
[PubMed]
110
Tierney
RT
,
Sitler
MR
,
Swanik
CB
,
Swanik
KA
,
Higgins
M
,
Torg
J
.
Gender differences in head-neck segment dynamic stabilization during head acceleration.
Med Sci Sports Exerc
.
2005
;
37
(
2
):
272
279
[PubMed]
111
Collins
CL
,
Fletcher
EN
,
Fields
SK
, et al
.
Neck strength: a protective factor reducing risk for concussion in high school sports.
J Prim Prev
.
2014
;
35
(
5
):
309
319
[PubMed]
112
Schmidt
JD
,
Guskiewicz
KM
,
Blackburn
JT
,
Mihalik
JP
,
Siegmund
GP
,
Marshall
SW
.
The influence of cervical muscle characteristics on head impact biomechanics in football.
Am J Sports Med
.
2014
;
42
(
9
):
2056
2066
[PubMed]
113
LaBella C, Henke N, Collins C, Comstock RD. A comparative analysis of injury rates and patterns among girls' soccer and basketball players at schools with and without athletic trainers from 2006/07–2008/09. American Academy of Pediatrics National Conference and Exhibition; October 20–23, 2012; New Orleans, LA
114
Knowles
SB
,
Marshall
SW
,
Bowling
JM
, et al
.
A prospective study of injury incidence among North Carolina high school athletes.
Am J Epidemiol
.
2006
;
164
(
12
):
1209
1221
[PubMed]

Competing Interests

POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

FINANCIAL DISCLOSURE: Dr. Meehan participates in research funded, in part, by the National Football League Players Association and receives compensation from ABC-Clio Publishing, Wolters Kluwer, and Springer International Publishing for his authored works. Dr. Landry has indicated he does not have a financial relationship relevant to this article to disclose.