Soccer is a high-to-moderate intensity contact/collision sport. Concussions can result from direct or indirect force transmitted to the head. There is a generalized consensus in the scientific community on the application of specific guidelines for education, detection, diagnosis, and treatment of concussions.1–4 Prevention remains a highly controversial topic.
There is little or no anecdotal evidence or statistical data indicating that purposeful heading is likely to lead to acute or cumulative brain damage. Most studies are either inconclusive or suggest that the speed and force associated with the purposeful heading of a ball are generally much lower than those required to cause a concussion.5–9
Despite the paucity in the concussion prevention literature and in response to a class action lawsuit, the United States Soccer Federation (USSF) adopted a policy6 that banned players under the age of 11 years from heading the ball, and for players between 11 and 13 years, the policy limited the number of headers they could perform during a practice. Because of its controversy, the topic sparked much debate with the American public. One of the most recent studies regarding concussion, which influenced the USSF's decision, involved a large retrospective analysis of longitudinal surveillance data from high schools. These data were collected between 2005 through 2014 and were analyzed by researchers at the University of Colorado and subsequently published in JAMA Pediatrics.10 The study reports that the rates of concussion in girls and boys are the second highest and fifth highest, respectively, among 9 examined sports. In 30.6% and 25.3% of the concussions among male and female players, the heading of the ball is recognized as the specific cause of the concussion. Athlete-to-athlete contact is the main cause of concussion in soccer, with an incidence of 68.8% for boys and 51.3% for girls. Concussions may also occur when the ball hits an unprepared player in the head,11 when a player's head hits the ground after a fall, or when a player hits a stationary object, such as a goalpost.
The University of Colorado study focused on high school soccer players, a heterogeneous group. Players differ greatly in their skills, time, and level spent playing the sport. Most importantly, on each team, there are players of different ages, from 14-year-old freshmen to 19-year-old seniors. The time between 14 and 19 years of age is a vital period of adolescence during which boys and girls experience their most significant physical development, emotional growth, and intellectual maturation. A 14-year-old player may have an elevated chance of injury in a collision with a 19-year-old player. In addition, a 14-year-old player may become injured when heading, deliberately or otherwise, a ball that has been kicked forcefully by a 19-year-old player. The Soccer Youth Federation is aware of these age-specific differences. All organizations, from in-house youth programs to travel clubs, private cup elite teams, and Olympic Development programs, divide their players by age groups. In contrast, high school programs promote the integration of age groups. Certain questions are pertinent:
Why are we arbitrarily targeting 13-year-old and under players, given that such players were not in the pool of players examined in the University of Colorado study?
Since the University of Colorado study was based on data collected from high schools, should we not target that specific level of competition?
When those 14-year-old underclassmen may start playing against juniors and seniors at varsity level, will they be exposed to potentially greater risks of all types of injuries, including concussion from heading the ball, a technique to which they have not been exposed?
Preventing injury, particularly concussion, in soccer at any age group has been elusive to say the least. Consequently, there is a large gap in the current literature regarding various approaches to concussion prevention. One meta-analysis published in the British Journal of Sports Medicine12 in June 2016 found 14 studies regarding concussion prevention through novel equipment (such as headgear and mouthguards); however, only 1 study could be found that looked at implementing concussion education and concussion training programs. A Swiss study13 published in 2002 in the American Journal of Sports Medicine found that implementing an injury prevention program at the youth soccer level significantly reduced injury overall, including head trauma and concussion. In all sports, the adolescent's musculoskeletal development, specific skills, the proper teaching of techniques, and vision for the game are developed and improved after countless training/teaching hours. Mastering these aspects of the game may also help to minimize the occurrence of undesirable incidents. The National Soccer Coaches Association of America (NSCAA) states, “Faulty techniques taught at a young age can lead to bad habits and perhaps even injury. It is recommended that the coach has significant knowledge of the techniques and how to practice them before undertaking teaching them to young players”.14 The use of the proper equipment is equally important to injury prevention. The specific ball size, type, and inflation, appropriate for the level of players “age, should always be used.” Fortunately, technology has been effective by triggering a move away from water-retaining leather balls, which had an increased mass and force of impact when wet, in favor of balls made of synthetic, water-resistant materials.15
Critical to injury prevention should be the concept of avoiding fatigue. A hockey-related concussion study in 2008 clearly showed a relationship between fatigue and concussion.16 There are significant differences between training and playing a regular game. Intensity and competitiveness, as well as mental and physical fatigue, are at different levels during a game than during training. Almost universally, athletes have their training during the entire week. Only 1 day is designated as “game day” for playing opposing teams. At high school level, in the United States, teams compete 2 to 3 times per week. A significantly high number of games played in a relatively short period is also observed at travel team and selective cup team levels. Players and families often travel several hours to participate in the many tournaments offered throughout the country during the spring and fall seasons. At times, these teams must play 2 games in a single day. Playing 3 to 5 games in the span of a weekend is the rule rather than the exception.
Soccer is played by 250 million players in more than 200 countries; with an estimated 3.5 billion fans, soccer is the world's most popular sport. The US Youth Soccer Registration of Players had 3 055 148 members in 2014. To better analyze the commonality of concussions throughout soccer, we must compare and contrast the American data with those of countries in which this sport has been played much longer and by many more.
Are concussions as common in other countries as in United States? If the sport is inherently problematic, we should observe similar statistics for concussion in every country. At present, no other federation in the world has adopted any limiting measures similar to those imposed by the USSF. We should acknowledge the lack of international research on concussion in soccer from countries where this sport is even more popular than in the United States. Is this related to a delayed interest in the scientific community, or those problems are not as frequent in models that significantly differ from ours? Limiting or banning certain technical aspects of the game may reassure us; however, different measures to prevent concussion may need to be adopted.
There are distinguishing features of the way in which the sport is played in the United States, overall: significant age differences among players and playing several games in rapid succession. Competition and agonistic interaction are clearly emphasized over development and training. These are likely causes of significant increase in fatigue and stress, with an equally important reduction in reaction and recovery time. Does this lead to an increased susceptibility to concussion? The lack of definite scientific data, and the difficulty of obtaining it, may leave us just with intuitive conclusions.
Selecting teams with players of similar age groups, avoiding multiple games during the week, avoiding tournaments, or at least decrease the number of games played in a weekend are all changes dictated by common sense that could provide a safer environment and decrease all types of injuries for all young athletes. We should focus more on proper training, prevention, diagnosis, and treatment. Redesigning the format of youth leagues, reviewing the current state of evidence on concussions, and designing long-term epidemiological studies, as advocated by the American Medical Society for Sports Medicine (AMSSM),17 will be key to implementing the most effective measures.
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