Fighting in ice hockey has persisted as a result of the expansion of professional leagues and rise in world-wide popularity of the game (1). Approximately 1.7 million people from 72 countries currently play ice hockey (2). The game has grown, but not in concert with our understanding of concussion science and factors that contribute to increased concussion risk. Concussion prevention is critical because of the serious short and long-term consequences of brain trauma and potential repercussions of repetitive subclinical forces (3–7). Mayo Clinic Ice Hockey Summit: Action on Concussion attendees in 2011, 2013, and 2017 prioritized elimination of fighting and all head hits as an essential concussion prevention strategy (4,8). Objectives of this article are to: understand how fighting is learned and why it continues, recognize the negative consequences of fighting and head trauma, and outline opportunities and barriers to end fighting and reduce all head hits in ice hockey.
How Is Fighting Learned and Why Does It Continue?
Fighting or “fisticuffs” in professional and amateur ice hockey is a complex and polarizing tradition. Ice hockey has allowed body checking and tolerated violence since its inception. The 1903 Stanley Cup finals was described as “grueling, mean, dirty, and played by a single line on a team and one goalie (9).” The four-game series between Winnipeg and Montreal was played on 3 inches of slushy ice over 6 d. Players were described as “faster,” but also “meaner” and prone to fighting. Professional and amateur hockey has grown since 1903 to include numerous teams with larger player rosters. At the same time, from the “Broad Street Bullies” of the Philadelphia Flyers to “The Code” and the rise of “enforcers,” fighting has evolved as both a form of intimidation and protection (10).
The National Hockey League (NHL) introduced rule 56 in 1922, which assessed a 5-min penalty to athletes who engaged in fighting (1). Additional penalties were added for behavior related to fighting in hockey, such as leaving the bench to fight and removing a player’s helmet. Recently, the NHL has given the officials more freedom to call penalties for instigating fights or wearing certain equipment during a fight. These rule changes have contributed in part to a recent decrease in the number of fights, but the tolerance for fighting in ice hockey continues to affect amateur and youth leagues.
Fighting in hockey is influenced by Bandura’s social modeling theory and behavioral reinforcement. Players aspiring for a college scholarship or an NHL career may emulate pro players. They often hone their skills in Junior hockey where fighting is still permitted. Role modeling, such as “Monkey See, Monkey Do,” shows that children mimic violent behavior after observing “Bobo” dolls being punched and kicked (11,12). Similarly, young players copy the NHL fights they see on television. Fight training is often a part of hockey camps, dryland training, and practices as players compete in a “toughness” pecking order. Junior A and NHL fights are tallied, along with height, weight, goals scored, and assists, on web sites, such as www.hockeyfights.com (13). Players willing to fight on behalf of the “team” are held in high regard by those who endorse fighting (14). Often, less skilled players assume the role of enforcers rather than have their hockey careers end. Male and female adolescents also may participate in a locker room game known as “Helmet and Gloves” or “Locker Room Boxing” (LRB) without the knowledge of their coach or parents (15).
International hockey, including the Olympic Games, is popular and showcases speed and skill while enforcing a no fighting rule. Data from 13 NHL seasons revealed that most fans do not want fighting (16). Although fighting may result in lower game attendance and less revenue, other fans support it, evidenced by the popularity of www.hockeyfights.com. Investigator Rockerbie concluded “fighting will remain in hockey until it negatively affects the NHL’s bottom line (16).” The class action suit filed against the NHL by 200 former players alleges exploitation, promotion of brutal on-ice behavior, and lack of player education on the potential consequences of repeated head trauma, which supports the elimination of fighting and head trauma in the sport.
The Negative Effects of Fighting and Head Trauma
A blow to the head or a blow to the body with force transmitted to the head produces both linear and rotational accelerations to the brain. A concussion can result from a direct blow to the head or from rapid acceleration and deceleration of the brain secondary to a blow to the body. The accelerations produced by common head trauma mechanisms in hockey have been identified and are outlined in Figure 1 (17). The angle, orientation, magnitude, and frequency of accelerations transmitted to the brain by a fall, contact from a puck, shoulder, or punch have been quantified (17). An unhelmeted fall to the ice with a head strike produces the highest angular acceleration. A punch to the head produces the next highest angular acceleration (17). Other impact characteristics, such as location, mass, velocity, surface compliance (stiffness), and impact vector influence the kinematics leading to brain tissue stress and strain. Dangerous punches, including the uppercut, thrown at an angle to the jaw cause very high rotational acceleration (17,000 rads·s2) (17). Hockey players wrestle, throw, and receive punches while balancing on skates, and often fall to the ice without a helmet on the head. This type of head contact with the ice, especially if the player has been rendered unconscious by a punch to the head, is perilous and potentially fatal. While accidental, unintended head trauma will occur in hockey, the blatant, illegal fighting behavior combined with the potentially devastating consequences, should not be encouraged nor allowed at any level of the sport.
Fighting and all other forceful contact to the head can result in serious injury to the brain from the high accelerations. The depiction of a brain cell (neuron) before and after blast trauma (bTBI) exposure (Fig. 2) with disabled dendrites and axon breakdown is believed to be very similar to what occurs from blows to the head in hockey. Soldiers exposed to bTBI have similar clinical consequences as players who sustain concussions in hockey (18,19).
Dementia Pugilistica, described in 1928, refers to the “punch-drunk syndrome” experienced by boxers who developed a neurodegenerative disease from repetitive head trauma (20). Chronic traumatic encephalopathy (CTE) has been recently identified by post mortem brain biopsy in former athletes who participated in collision sports (21–23). CTE was documented on autopsy in four junior hockey players who committed suicide before age 30 years (24).
Repetitive concussive and subconcussive head impacts in American football players, quantified by a cumulative head impact index, are associated with cognitive and neurobehavioral consequences such as depression, behavioral dysregulation, and cognitive impairment later in life (25). Moreover, animal models have demonstrated that closed head impacts (CHI) can lead to the sequelae associated with CTE even in the absence of concussive signs (26). The number of concussions experienced by some hockey players is of great concern. The Junior A players in our research cohort (age, 16–21 years) reported up to six previous concussions (27). The known discrepancy between reported and undisclosed concussive injuries in contact/collision sports undoubtedly underestimates the true incidence of concussion.
Relating Head Accelerations to Concussion
Our Junior A hockey concussion research in athletes ages 16 to 21 over the past 6 years utilized instrumented helmets (2011–2013) or Triax head band accelerometers (2016–2017) to measure both linear and rotational head acceleration (27). The maximum single rotational (rads·s2) and linear (g) accelerations were plotted on Zhang’s concussion scale for each player with a diagnosed concussion. Five of the six reported concussions in 2011 to 2012 were associated with accelerations above the 80% probability threshold; however, there also were several players above the 80% threshold without a concussion diagnosis. Ten of the remaining 24 players sustained impacts at or above the 80% probability threshold for linear acceleration (g). Additionally, 16 of the remaining 24 players sustained impacts with resultant rotational accelerations (radian·s2) at or above the 80% probability threshold. The Zhang scale is not intended to imply that a single high acceleration was the sole cause of the concussion.
Our observation that a high force magnitude recorded in some players without a diagnosis of a concussion prompted further investigation using a “head form” drop test. A hockey helmet with instrumented technology (Head Impact Telemetry System (HITS)) was placed on a similarly instrumented Hybrid III Head Form. The drop testing was performed to ensure validity of the instrumented helmet since a concussion was not always diagnosed in the Junior A players despite high acceleration measurements. The drop test results showed congruency between the instrumented helmet and the Hybrid III head form. This observation prompted our team to challenge the sensitivity of the tools currently used to diagnose a concussion (28).
Subjective concussion diagnosis can be inaccurate, leading to both underdiagnosis and overdiagnosis and leaving the true prevalence of concussion unknown (27,29). Some players who experience high accelerations are able to deny or mask their symptoms to avoid detection. Tests, such as the Sideline Concussion Assessment Tool (versions 2, 3, and 5), may not always detect a concussion (30,31). Neuropsychological tests are not used to diagnose a concussion, but have value in return-to-play decision making. Concussion detection continues to improve as a result of educational efforts and emerging objective diagnostic tests (29,30,32–34). An accurate and reliable objective diagnosis of concussion (ODC) is essential for removal from play, treatment initiation, evaluation of therapeutic effectiveness, and accurate assessment of preventative interventions, such as rule changes (35). For example, if an ODC (27) is in place, examining the number of concussions before and after a no fighting rule change would be a valid comparison. A recent systematic review of advanced neuroimaging, fluid biomarkers, and genetic testing in sport-related concussion assessment provides support for an ODC (36). The use of blood biomarkers, neuroimaging, neurophysiologic assessments, and tests of oculomotor functioning are showing promise as objective diagnostic markers of concussion in our investigations.
Opportunities and Barriers to End Fighting
The objective evidence of brain damage from fighting and other repetitive head trauma is worrisome. Accurate diagnosis and prompt treatment of concussions are important to mitigate the oxidative crisis and other effects within the brain, but major efforts must be directed to minimize the risk of concussion, including exposure to fighting and hits to the head. Hockey stakeholders must unite to reduce the circumstances leading to multiple concussion injuries and repetitive, subclinical brain trauma.
Ken Dryden, an attorney and former NHL player, detailed the increase in frequency and intensity of fighting in the NHL. A current player may absorb several potentially concussive blows in a single shift. Dryden challenges the NHL to “Save a Great Game” and take all head hits out of the game. In Dryden’s opinion, support from the medical community will be necessary for the NHL to stop head hits (37). A comprehensive approach to end fighting in hockey will require focused education, enforcement of existing rules, enacting new rules, and promoting behavioral modification for sportsmanship and mutual respect (38,39).
Each intervention to decrease concussion should be evaluated by objective, measurable outcomes to demonstrate effective injury reduction. The number of fights, penalties, and injuries that occur before and after rule changes and head trauma prevention strategies are simple measurable outcomes. Fights and penalties can be tracked through scoresheet analysis submitted from amateur and professional leagues. Injury tracking would require access to the players’ medical records by trained medical professionals to be logged into a Health Insurance Portability and Accountability Act-compliant database.
Inconsistent Fighting Rules
Rigorous rule enforcement can reduce head trauma risk and promote a culture of safety for players. The NHL has a 5-min major penalty for fighting that has not changed since 1922 (Table). Subsequent rule additions, such as penalizing the “third man” joining a fight have not measurably reduced the number of fights. In stark contrast, fighting is strictly prohibited in youth, high school, collegiate (National Collegiate Athletic Association) hockey, European professional leagues, International Ice Hockey Federations (IIHF) tournaments, and the Olympic Games (see Table). Fighting is penalized in these contests by ejection from the game, which is similar to all other sports.
Junior hockey is an exception to the amateur rules and fighting tolerance varies by league and tier. A tier 3 junior hockey team had 47 fights during the 2011 to 2012 season and 34 fights during the 2012 to 2013 season (27). Multiplied across all junior hockey teams in the United States and Canada, these numbers imply a staggering prevalence of potential head trauma from fighting. In 2015, U.S. Hockey instituted a major penalty and 10-min misconduct for fighting in tiers 1 and 2 junior hockey and a game misconduct for fighting in tier 3 junior hockey. In addition, a second fighting major results in a three-game suspension and a third fighting major results in an indefinite suspension until a league hearing is conducted. The Ontario Hockey League (OHL) now suspends a player with three fights during the season for two games after each subsequent fight. Recently, implemented progressive suspensions for fighting in tier 1 junior hockey has resulted in fewer altercations per season. The number of fights in the United States Hockey League decreased from 600 in 2012 to 180 in 2015 and in the OHL from 1600 in 2004 to 320 in 2016.
The association between fighting and concussion is intuitively obvious, but documenting and quantifying the diagnosis is a challenge. Accurate epidemiological data on the incidence and mechanism of concussion are not currently available. The NHL Concussion Policy requires a “quiet room” evaluation for any player who exhibits observable signs of concussion. However, players who engage in a fight are sent directly to the penalty box instead of the “quiet room” for a concussion evaluation, despite the obvious blows to the head. This protocol may result in underdiagnosing and detection bias.
Implementing game ejections for fighting, along with monetary fines and suspensions for repeat offenders, would reduce these behaviors. A more progressive rule with a one-game suspension for each offense, similar to the NCAA, would be even more effective. NCAA hockey reported only 20 fights over a 4-year span compared with 3,091 fights in the NHL during the same period (40).
LRB/Helmet and Gloves
Youth hockey players, coaches, managers, and parents have been advised not to engage in or promote fighting or fight training on or off the ice. LRB is a dangerous drill that occurs before or after hockey practices and in hotels during tournaments (15). This behavior often occurs when coaches and parents are absent and also may be part of a hazing ritual for some teams. The perceived need for fight training would disappear if fighting was not allowed and heavily penalized. LRB must be strictly forbidden at all levels of hockey.
Officiating — Enforcing the Rules
Support for game officials by players, coaches, and parents is essential. Officials must be able to call penalties according to the accepted rules. Respect for officials and rigorous enforcement of the existing rules promotes hockey safety.
Education and Behavior Modification (Fair Play)
In 2004, MN Hockey and Mayo Clinic Sports Medicine launched Fair Play (FP), a behavioral modification program (38). FP rules were first introduced in Quebec, after youth hockey registrations dropped by 100,000 players from 1980 to 1990. Decreased participation was attributed to injuries, violence, and aggressive rule infractions. FP was introduced to reduce aggressive behavior in hockey by increasing the emphasis on sportsmanship (39). A FP point (FPP) is forfeited if a predetermined sum of penalty minutes is exceeded by the team during a game. FPPs earned are counted in the season standings and influence which teams advance into the end of season tournaments. A medically monitored study in Minnesota on Junior Gold players (high school age) showed a fourfold decrease in penalties and injuries, including concussions, when teams played by FP rules (41). A study of tournaments played under Intensified FP rules showed injury rates five times higher for highly penalized teams compared to teams complying with the rules (38). Although FP, officially launched in 2004, tracked winning or losing an FPP on score sheets at each game, many hockey stakeholders were not aware of FP’s power to modify player, coach, and parent behavior. Thus, during the research study described, at tournaments run by Intensified FP, FP materials were distributed, pregame sportsmanship announcements were read, and the impact of FP points earned and lost on influencing which teams advanced was displayed. Large scoreboards notified attendees “out of control players, parents, and coaches” could be removed from the arena if their behavior was not respectful.
The 5:1 injury ratio for highly penalized teams, albeit in a smaller population studied, was higher than the 3:1 ratio shown by Emery comparing body checking to no body checking in Peewee hockey leagues (42). Teams with the majority of penalties and the most forfeited FPPs sustained the most injuries (38).
Delay Body Checking in Games until Age 15 Years
Participation in leagues that permit body checking has been identified as the most consistent risk factor for injury and concussion in youth ice hockey (43,44). A viable strategy to reduce head contact in youth hockey is to remove body checking from games at the Bantam level. USA Hockey and Hockey Canada adopted a new rule several years ago that delayed checking in games until age 13 years. Elimination of body checking at the Peewee level (ages 11–12 years) reduced concussion risk threefold and also reduced severe concussion compared with leagues allowing body checking (45). Subsequent research confirmed a 67% reduction in concussion risk in a Peewee league with “no body checking” (46). Additional research at the nonelite Bantam level showed a significant decrease in injuries, fewer high impact collisions, a 57% reduction in concussion, and no changes in performance metrics. These data support eliminating body checking for this age group (44). Eliminating body checking in games reduces the fear associated with collisions and allows players to “play the puck,” thereby promoting skill development. A highly prioritized action item to prevent injury, at Summit III: Action on Concussion, hosted at the Mayo Clinic in September 2017, was eliminating body checking in Bantam hockey (8). The game remains physical with incidental contact, but forceful body checking must be replaced by safer contact. An example of a less injurious body collision is angling or using the body in a less forceful contact, called a “rub-out” along the boards. The goal of angling or a rub-out is simply to obtain puck possession. Young players can maintain momentum and control the puck when their focus is not on “finishing the body check.”
Ice hockey is a fast and exciting sport that requires skill, finesse, and teamwork. There is simply no excuse for allowing fighting and head hits with our current knowledge of concussion and potential long term consequences. Better to serve the penalty for unchecked aggression at the time of rule infraction than to defer the consequences of repeated head trauma to later in life.
The future growth of hockey and health of the players depend on improving on-ice safety, reducing the risk of concussion, and premature retirement from sports. Dangerous infractions, such as fighting, hits to the head, charging, boarding, and checking from behind must be eliminated. Important strategies are readily available, including the enforcement of existing rules, implementation of new rules to penalize fighting and head hits, implementing FP programs, and delay of body checking in games to older age groups. Evaluating the outcomes of these initiatives with objective concussion diagnoses will demonstrate their effectiveness and lead to additional safety improvements. It may be possible in the future to equip all hockey players with a wearable sensor that accurately measures linear and rotational forces to the head. Head impact exposure data may become a reliable and useful tool to guide decision making.
Current player conduct and administrative indifference in professional and some Junior A hockey leagues condone and even promote fighting. This practice undermines sportsmanship and provides negative role modeling for young players. The biomechanics of head blows during a hockey fight combined with the risk of falling to the ice with or without a helmet results in dangerously high and potentially fatal levels of force transmission to the brain. The most obvious and immediately effective approach is to eliminate fighting and all head hits from the sport of ice hockey.
The authors declare no conflict of interest and do not have any financial disclosures.
1. Rockerbie D. The demand for violence in hockey. The Economics of Sport
. 2012; 1:159–76.
2. Merk M. International Ice Hockey Federation. March 20, 2016. [cited 2018 Nov 7]. Available from: http://www.iihf.com/2016
3. Balmakund J. Sports concussion. J. Ark. Med. Soc
. 2013; 110:92–4. PubMed PMID: 24383198.
4. Smith AM, Stuart MJ, Dodick DW, et al. Ice Hockey Summit II: zero tolerance for head hits and fighting. Clin. J. Sport Med
. 2015; 25:78–87.
5. Basen R. Neurocognitive tests for concussion—wave of the past? Front. Neurol
. 2017; 4:1–7.
6. Munce TA, Dorman JC, Thompson PA, et al. Head impact exposure and neurologic function of youth football players. Med. Sci. Sports Exerc
. 2015; 47:1567–76.
7. Siman R, Giovannone N, Hanten G, et al. Evidence that the blood biomarker SNTF predicts brain imaging changes and persistent cognitive dysfunction in mild TBI patients. Front. Neurol
. 2013; 4:190.
8. Mayo Clinic. Ice Hockey Summit III: action on concussion prioritized action items. 2017. [cited 2018 Nov 7]. Available from: https://ce.mayo.edu/sports-medicine/content/mayo-clinic-sports-medicine-ice-hockey-summit-iii-action-concussion-2017
9. Smith AM. Power Play: Mental Toughness for Hockey and Beyond
. 3rd ed. Montgomery (AL): Athletic Guide Publishing; 2000. 258 p.
10. Bernstein R. The Code: The Unwritten Rules of Fighting and Retaliation in the NHL
. Chicago (IL): Triumph Books; 2006.
11. Bandura A, Walters RH. Social Learning Theory
. Englewood Cliffs (NJ): Prentice-Hall; 1977.
12. Bandura A, Adams NE, Beyer J. Cognitive processes mediating behavioral change. J. Pers. Soc. Psychol
. 1977; 35:125.
13. Hockey Fights.com
Web site [Internet]. [cited 2018 Nov 7]. Available from: http://www.hockeyfights.com/
14. Branch J. Boy on Ice: The Life and Death of Derek Boogaard
. WW Norton & Company 2014.
15. Gordon KE, Gay TL, McTimoney M. Helmet and gloves: a new piece of the concussion puzzle. Clin. J. Sport Med
. 2006; 16:195–8.
16. Rockerbie DW. Fighting as a profit maximizing strategy in the National Hockey League: more evidence. Appl. Econ
. 2016; 48:292–9.
17. Kendall M. Comparison and characterization of different concussive brain injury events
. University of Ottawa, 2016.
18. Chen Y, Huang W, Constantini S. The differences between blast-induced and sports-related brain injuries. Front. Neurol
. 2013; 4:119. Epub 2013/08/24. doi: 10.3389/fneur.2013.00119. PubMed PMID: 23966976; PubMed Central PMCID: PMCPMC3743039.
19. Hemphill MA, Dabiri BE, Gabriele S, et al. A possible role for integrin signaling in diffuse axonal injury. PLoS One
. 2011; 6:e22899.
20. Jordan BD. Dementia pugilistica. J. Neurol. Sci
. 1994; 127:6.
21. Omalu BI, DeKosky ST, Minster RL, et al. Chronic traumatic encephalopathy in a National Football League player. Neurosurgery
. 2005; 57:128–34.
22. McKee AC, Cantu RC, Nowinski CJ, et al. Chronic traumatic encephalopathy in athletes: progressive tauopathy after repetitive head injury. J. Neuropathol. Exp. Neurol
. 2009; 68:709–35.
23. McKee AC, Daneshvar DH, Alvarez VE, Stein TD. The neuropathology of sport. Acta. Neuropathol. (Berl)
. 2014; 127:29–51.
24. Westhead R. Four junior hockey players diagnosed with CTE, researcher says. April 21, 2017. [cited 2018 Nov 7]. Available from: https://www.tsn.ca/four-junior-hockey-players-diagnosed-with-cte-researcher-says-1.730445
25. Montenigro PH, Alosco ML, Martin BM, et al. Cumulative head impact exposure predicts later-life depression, apathy, executive dysfunction, and cognitive impairment in former high school and college football players. J. Neurotrauma
. 2017; 34:328–40.
26. Tagge CA, Fisher AM, Minaeva OV, et al. Concussion, microvascular injury, and early tauopathy in young athletes after impact head injury and an impact concussion mouse model. Brain
. 2018; 141:422–58.
27. Smith AM, Stuart MJ, Roberts WO, et al. Concussion in ice hockey: current gaps and future directions in an objective diagnosis. Clin. J. Sport Med
. 2017; 27:503–9.
28. Jorgensen JK, Thoreson AR, Stuart MB, et al. Interpreting oblique impact data from an accelerometer-instrumented ice hockey helmet. Proceedings of the institution of mechanical engineers, part P. J. Sports Eng. Technol
. 2017; 231:307–16.
29. McCrea M, Meier T, Huber D, et al. Role of advanced neuroimaging, fluid biomarkers and genetic testing in the assessment of sport-related concussion: a systematic review. Br. J. Sports Med
. 2017; 51(2):919–29.
30. Siman R, Shahim P, Tegner Y, et al. Serum SNTF increases in concussed professional ice hockey players and relates to the severity of postconcussion symptoms. J. Neurotrauma
. 2015; 32:1294–300.
31. Echemendia RJ, Meeuwisse W, McCrory P, et al. The sport concussion assessment tool, 5th ed. (SCAT5): background and rationale. Br. J. Sports Med
. 2017; 51:848–50: bjsports-2017-097506.
32. Daley M, Dekaban G, Bartha R, et al. Metabolomics profiling of concussion in adolescent male hockey players: a novel diagnostic method. Metabolomics
. 2016; 12:185.
33. Ghosh Hajra S, Liu CC, Song X, et al. Developing brain vital signs: initial framework for monitoring brain function changes over time. Front. Neurosci
. 2016; 10:211.
34. Galetta MS, Galetta KM, McCrossin J, et al. Saccades and memory: baseline associations of the king–Devick and SCAT2 SAC tests in professional ice hockey players. J. Neurol. Sci
. 2013; 328:28–31.
35. Mrazik M, Perra A, Brooks BL, Naidu D. Exploring minor hockey players’ knowledge and attitudes toward concussion: implications for prevention. J. Head Trauma Rehabil
. 2015; 30:219–27. doi:http://dx.doi.org/10.1097/HTR.0000000000000018. PubMed PMID: 24590152.
36. Fickling SD, et al. Objective evidence of subconcussive impairment in brain vital signs after one season of competitive ice hockey. 2017.
37. Dryden K. Game Change: The Life and Death of Steve Montador, and the Future of Hockey
. Kenya (Africa): Signal Publishers; 2017. 368 p.
38. Smith AM, Gaz DV, Larson D, et al. Does fair play reduce concussions? A prospective, comparative analysis of competitive youth hockey tournaments. BMJ Open Sport Exerc. Med
. 2016; 2:e000074.
39. Vaz EW, Clarke W. The Professionalization of Young Hockey Players
. Lincoln (NE): University of Nebraska Press; 1982.
40. Schlossman B. NCAA can’t feel this fighting anymore: college hockey doesn’t miss it, but why haven’t other hockey leagues followed suit? Duluth News Tribune
. December 31, 2016. [cited 2018 Nov 7]. Available from: http://www.duluthnewstribune.com/sports/hockey/4190489-ncaa-cant-feel-fighting-anymore-college-hockey-doesnt-miss-it-why-havent-other
41. Roberts WO, Brust JD, Leonard B, et al. Fair-play rules and injury reduction in ice hockey. Arch. Pediatr. Adolesc. Med
. 1996; 150:140–5.
42. Black AM, Hagel BE, Palacios-Derflingher L, et al. The risk of injury associated with body checking among peewee ice hockey players: an evaluation of Hockey Canada’s national body checking policy change. Br. J. Sports Med
. 2017; 51:1767–72. bjsports-2016-097392.
43. Committee on Sports Medicine and Fitness. Safety in youth ice hockey: the effects of body checking. Pediatrics
. 2000; 105:657–8.
44. Black A, Palacios-Derflingher L, Schneider KJ, et al. The effect of a national body checking policy change on concussion risk in youth ice hockey players. Br. J. Sports Med
. 2017; 51:A70–1.
45. Trudel P, Bernard D, Boileau R, Marcotte G. Effects of an intervention strategy on body checking, penalties, and injuries in ice hockey. In: Ashare AB, editor. Safety in Ice Hockey
. 3rd ed. ASTM International
. 2000. p 237.
46. Black AM, Macpherson AK, Hagel BE, et al. Policy change eliminating body checking in non-elite ice hockey leads to a threefold reduction in injury and concussion risk in 11- and 12-year-old players. Br. J. Sports Med
. 2016; 50:55–61.