Pediatric and adolescent sports participation has increased with a concomitant increase in injuries. Sports have transitioned from recreational to deliberate, structured activities wherein success is determined by achievement of ‘elite’ status. This has led to specialization in a single sport with intensive, repetitive activity at younger ages causing physical and emotional consequences, particularly true for the growing athlete who is particularly susceptible to injury. Clinicians caring for this population must understand the epidemiology of youth sports specialization, the unique physiology/structure of this age group, and the potential physical and emotional consequences.
Key points
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An increasing number of youth are specializing in single sports at younger ages and engaging in repetitive, intensive activity.
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Early, single sport specialization has not been shown to improve future athletic performance, but has been shown to be detrimental both physically and emotionally.
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The adolescent growth spurt is a particularly vulnerable period of time for the youth athlete with repetitive microtrauma, placing the body at risk structurally.
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Identifying burnout is critical for the clinician taking care of youth athletes who specialize in a single sport.
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Long-term consequences extending into adulthood exist for the athlete who specializes at a young age.
Epidemiology of youth sports participation
Organized sports participation among young athletes has increased tremendously over the past several years. According to the National Council on Youth Sports, nearly 60 million youth between the ages of 6 to 18 participated in organized athletics in 2008 compared with 52 million in 2000. This rise has occurred with a concurrent drop in school-based physical education, with only 29% of all high school students participating in daily classes. This has created an environment in which sports activity is highly structured and centered on the development of specific skills (eg, pitching, tumbling, dribbling) rather than a strong foundation centered around core physical principles, such as flexibility, endurance, and balance. This trend from unstructured free play to deliberate, adult activity has been well-documented in the media, and has occurred simultaneously with youth sports becoming a profitable business entity.
As a result, a culture has been created in which the definition of success in youth sports is defined not by laying the foundation for a healthy lifestyle, but rather the attainment of “elite” status. This push has been largely created by coaches and parents, many of whom measure their child’s athletic participation by the attainment of collegiate scholarships and professional contracts. In 1993, Ericsson and colleagues proposed that, to achieve expertise as a musician, one must practice 10,000 hours within that specialized field. This principle has been adopted by many parents as a justification for intensive, adult-style training for sports at increasingly younger ages. As a result, rather than playing a wide variety of sports at a moderate level of intensity during the early stages of physical development, there is increasing evidence that children are beginning to specialize at younger ages in 1 sport. This trend is occurring even with multiple groups advocating delayed specialization.
Single sport specialization can be defined as intensive, year-round training in a single sport at the exclusion of other sports. This phenomenon is especially present in the media, whose attention is focused on athletic prodigies such as Tiger Woods, who are applauded for their dedication to a single sport as toddlers, rather than athletes, such as Steve Nash and Roger Federer, who have achieved similar levels of success while playing multiple sports in their youth. Unfortunately, the desire to specialize is fallacious on multiple fronts.
First, the probability of achieving elite status is small for the vast majority of athletes. According to data published by the National Collegiate Athletic Association in 2013, the estimated probability of competing in collegiate athletics for high school athletes ranged from 3.3% to 6.8% for men’s basketball, women’s basketball, football, baseball, and men’s soccer. For that same group of sports, the estimated probability of competing at the professional level for high school athletes ranged from 0.03% to 0.5%. When these data are coupled with the fact that the average athletic scholarship is approximately $10,000, there is clearly a disconnect between the realistic chances of playing at the next level and, if one does make it, the rather modest amount of money that will be obtained. However, the argument could be made by some that, although the proposed rewards of single sport specialization are difficult to obtain, there exists either no other means to achieve that goal and/or the negative effects of attempting to achieve that path are minimal. The literature suggests otherwise.
From a theoretic perspective, Abernathy et al have suggested that diversified sport training in early and middle adolescence may better foster elite athletic potential than specialization owing to a more positive transfer of skills. Looking at the youngest of cohorts, Fransen and colleagues analyzed 735 boys aged 10 to 12 years of age and found that those who participated in various sports performed better on a standing broad jump and gross motor coordination than those who specialized in a single sport. Gullich and Emrich examined athletic performance in Germany and found that the younger the age of recruitment of the athlete into specialized training programs, the earlier they left sports. Those athletes who progressed to higher levels of participation began playing sports at later ages.
At the collegiate level, DiFiori examined a cohort of Division I athletes at their institution and found that 88% had participated in 2 to 3 sports as children, with the vast majority (70%) not specializing until the age of 12. In addition, the average age of specialization between collegiate athletes (15.4 years) and noncollegiate athletes (14.2 years) varied significantly. Malina also found that, among female collegiate athletes in the United States (particularly diving, tennis, golf, track and field, basketball, and volleyball), the majority had their first organized sporting experience in another sport. In addition, Vaeyens and colleagues found that an early age of onset of high-volume, sport-specific training did not necessarily associate with success at the international level in adult sporting activity. Thus, the proposed benefits of single sport specialization are minimal.
In addition, there are multiple studies that document the overall negative effects of sports specialization in the context of limited future gain. Jayanthi and colleagues examined more than 1200 athletes between the ages of 8 and 18, and found that athletes who spend more hours per week playing their sport than their age are 70% more likely to experience a severe injury. In addition, Holt and colleagues found that youth athletes of higher socioeconomic status (and with private health insurance) suffered more serious overuse injuries, particularly because they were the group that demonstrated a trend toward more sports specialization and less free play. Combined with the risks of social isolation, overdependence, burnout, and manipulation, the benefits of single sport specialization must be carefully considered within the context of the published risk, many of which are discussed in detail herein.
Epidemiology of youth sports participation
Organized sports participation among young athletes has increased tremendously over the past several years. According to the National Council on Youth Sports, nearly 60 million youth between the ages of 6 to 18 participated in organized athletics in 2008 compared with 52 million in 2000. This rise has occurred with a concurrent drop in school-based physical education, with only 29% of all high school students participating in daily classes. This has created an environment in which sports activity is highly structured and centered on the development of specific skills (eg, pitching, tumbling, dribbling) rather than a strong foundation centered around core physical principles, such as flexibility, endurance, and balance. This trend from unstructured free play to deliberate, adult activity has been well-documented in the media, and has occurred simultaneously with youth sports becoming a profitable business entity.
As a result, a culture has been created in which the definition of success in youth sports is defined not by laying the foundation for a healthy lifestyle, but rather the attainment of “elite” status. This push has been largely created by coaches and parents, many of whom measure their child’s athletic participation by the attainment of collegiate scholarships and professional contracts. In 1993, Ericsson and colleagues proposed that, to achieve expertise as a musician, one must practice 10,000 hours within that specialized field. This principle has been adopted by many parents as a justification for intensive, adult-style training for sports at increasingly younger ages. As a result, rather than playing a wide variety of sports at a moderate level of intensity during the early stages of physical development, there is increasing evidence that children are beginning to specialize at younger ages in 1 sport. This trend is occurring even with multiple groups advocating delayed specialization.
Single sport specialization can be defined as intensive, year-round training in a single sport at the exclusion of other sports. This phenomenon is especially present in the media, whose attention is focused on athletic prodigies such as Tiger Woods, who are applauded for their dedication to a single sport as toddlers, rather than athletes, such as Steve Nash and Roger Federer, who have achieved similar levels of success while playing multiple sports in their youth. Unfortunately, the desire to specialize is fallacious on multiple fronts.
First, the probability of achieving elite status is small for the vast majority of athletes. According to data published by the National Collegiate Athletic Association in 2013, the estimated probability of competing in collegiate athletics for high school athletes ranged from 3.3% to 6.8% for men’s basketball, women’s basketball, football, baseball, and men’s soccer. For that same group of sports, the estimated probability of competing at the professional level for high school athletes ranged from 0.03% to 0.5%. When these data are coupled with the fact that the average athletic scholarship is approximately $10,000, there is clearly a disconnect between the realistic chances of playing at the next level and, if one does make it, the rather modest amount of money that will be obtained. However, the argument could be made by some that, although the proposed rewards of single sport specialization are difficult to obtain, there exists either no other means to achieve that goal and/or the negative effects of attempting to achieve that path are minimal. The literature suggests otherwise.
From a theoretic perspective, Abernathy et al have suggested that diversified sport training in early and middle adolescence may better foster elite athletic potential than specialization owing to a more positive transfer of skills. Looking at the youngest of cohorts, Fransen and colleagues analyzed 735 boys aged 10 to 12 years of age and found that those who participated in various sports performed better on a standing broad jump and gross motor coordination than those who specialized in a single sport. Gullich and Emrich examined athletic performance in Germany and found that the younger the age of recruitment of the athlete into specialized training programs, the earlier they left sports. Those athletes who progressed to higher levels of participation began playing sports at later ages.
At the collegiate level, DiFiori examined a cohort of Division I athletes at their institution and found that 88% had participated in 2 to 3 sports as children, with the vast majority (70%) not specializing until the age of 12. In addition, the average age of specialization between collegiate athletes (15.4 years) and noncollegiate athletes (14.2 years) varied significantly. Malina also found that, among female collegiate athletes in the United States (particularly diving, tennis, golf, track and field, basketball, and volleyball), the majority had their first organized sporting experience in another sport. In addition, Vaeyens and colleagues found that an early age of onset of high-volume, sport-specific training did not necessarily associate with success at the international level in adult sporting activity. Thus, the proposed benefits of single sport specialization are minimal.
In addition, there are multiple studies that document the overall negative effects of sports specialization in the context of limited future gain. Jayanthi and colleagues examined more than 1200 athletes between the ages of 8 and 18, and found that athletes who spend more hours per week playing their sport than their age are 70% more likely to experience a severe injury. In addition, Holt and colleagues found that youth athletes of higher socioeconomic status (and with private health insurance) suffered more serious overuse injuries, particularly because they were the group that demonstrated a trend toward more sports specialization and less free play. Combined with the risks of social isolation, overdependence, burnout, and manipulation, the benefits of single sport specialization must be carefully considered within the context of the published risk, many of which are discussed in detail herein.
Anatomy and physiology of the pediatric athlete
To more fully understand the potential consequences of single sport specialization on the pediatric and adolescent athlete, it is first critical to understand the physiologic and structural differences between the immature and mature athlete. Although there is no consensus on when sport specialization can safely occur, the age of 12 is generally used as a rough cutoff. This point is largely the age at which puberty and skeletal maturation begins.
From a physiologic standpoint, aerobic (V o 2 max) and anaerobic capacity increase with age, youth athletes have a higher metabolic cost of running compared with adults, and they have more difficulty dealing with thermoregulation. These are critical to understand when treating athletes who may be subjecting themselves to the intense demands of single specialization beyond the more commonly known overuse syndromes discussed herein.
From an orthopedic standpoint, the adolescent growth spurt is a critical time for athletic specialization. During this period, there exists a high risk of injury, particularly involving the apophysis and physis, when repetitive activity is performed. Multiple studies have demonstrated that the cartilage present about the physis, apophysis, and articular surfaces are more prone to injury (owing to a decreased resistance to force) during rapid growth phases. This is particularly demonstrated by the predisposition of athletes of this age group to suffer injuries to the apophyseal, physeal, and cartilaginous regions (ie, gymnast wrist, Osgood-Schlatter disease, osteochondral lesions).
Hawkins and Metheny outline the following concepts regarding these injuries. It is during rapid periods of growth that muscles and tendons lengthen, yet muscle hypertrophy does not occur at the same rate. As a result, muscles need to produce a greater percentage of their maximal force to produce the same movements that occurred before the growth spurt. This increased force is seen by the tendons. As an example, Hawkins and Metheny calculated that 30% more muscular force is potentially required to develop the same lower leg angular acceleration for an activity such as kicking a ball after a growth spurt as compared with before the growth spurt. If an athlete can generate this force, it is then also transferred to tendons and subsequently the apophyses, potentially leading to overuse injuries if the activity is performed repetitively. If these principles are understood, activities such as strength training can be performed as long as a preparticipation medical evaluation takes place, overall body conditioning is emphasized, and maximal lifts and power lifting are avoided until skeletal maturity is achieved.
The unique anatomy and physiology of the growing athlete places them at a baseline injury risk, which is multiplied by engaging in repetitive, intense activity that can occur with sport specialization.
Consequences of single sport specialization
Physical
Single sport specialization alone is not a problem; rather, the intensive, year-round training in a single sport at the exclusion of other sports causes these issues. Continuous single sport participation subjects the body to the same, repetitive microtrauma and overuse. General guidelines to avoid problems include limiting overall weekly and yearly participation time, limiting repetitive movement (eg, pitching counts), and allowing for scheduled rest periods and/or cross-training during “rest” periods. These recommendations must be individualized based on the athlete, their stage of skeletal maturity (especially during the adolescent growth spurt), and overall conditioning. When uncontrolled or unregulated training occurs, there are serious physical, emotional, and social consequences for both immediate and long-term sports participation.
There is a clear correlation in the literature between training volume and intensity and injury risk, particularly overuse injuries. In fact, the vast majority of injuries seen in a typical sports medicine clinic treating patients from ages 6 to 18 are related to overuse, up to 54.4% in some studies. Furthermore, according to Rose and colleagues in a study of 2721 high school athletes, there was a direct correlation of injury risk with increased weekly hours of sports participation. It therefore follows that, with single sport specialization, there not only exists a greater intensity and volume of training, but also an intensity and volume of training that is repetitive and leads to microtrauma.
For example, Jayanthi and colleagues found that in junior elite tennis players the risk of a reported injury was 1.5 times more likely if they specialized only in tennis. Pitching represents perhaps an even more extraordinary case. Fleisig and colleagues examined 481 youth pitchers (ages 9–14) over a 10-year period and found that pitching more than 100 innings per year increased injury risk 3.5 times. This effect of overuse is further exemplified in a case control study that compared injured and noninjured adolescent pitchers. The study found that the injured group pitched significantly more months per year, games per year, innings per game, pitches per game, pitches per year, and warmup pitches before a game. These pitchers were also more frequently starting pitchers, pitched in more showcases, pitched with higher velocity, and pitched more often with arm pain and fatigue. Clearly, specialization and injury risk are linked.
With regard to the specific injuries seen, the areas of the body that are most prone to overuse injury from repetitive trauma from single sport specialization in the growing athletes, as mentioned previously, are the apophysis and physis. This concentration leads to a spectrum of common conditions, including Osgood-Schlatter disease (tibia tubercle apophysitis), Sever disease (calcaneal apophysitis), and Little League elbow (medial epicondyle apophysitis). Physeal injuries such as Little League shoulder (proximal humeral physis) and gymnast wrist (distal radius physis) are also part of this spectrum of injury. Injuries to the cartilage of developing joint surfaces (osteochondral lesion) can also occur. As patients mature, they become more susceptible to adult injury patterns, including stress reactions and stress fractures of the spine (spondylolysis), femoral neck, patella, anterior tibia, medial malleolus, and foot ( Box 1 ).
Physical
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Osgood-Schlatter disease
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Sever disease
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Medial epicondyle apophysitis
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Distal radial physeal stress syndrome
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Proximal humeral physiolysis
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Stress fracture (ie, spondylolysis)
Emotional
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Burnout
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Social isolation
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Overdependence
Two specific areas of concern that have arisen with the increase in single sport specialization and warrant special consideration are the increasing rate of ulnar collateral ligament injuries in pitchers and traumatic knee injuries (ie, anterior cruciate ligament [ACL] tears). An increasing number of ulnar collateral ligament injuries are being seen in patients in younger and younger ages with specialization and overuse cited as the main culprits.
From a knee standpoint, Hall and colleagues examined 546 female basketball, soccer, and volleyball players, and found that those athletes involved in a single sport had 1.5-fold relative risk increased risk of patellofemoral pain, Osgood-Schlatter disease, and Sinding Larsen-Johansson syndrome compared with multisport athletes. This distinction is critical, because it has been noted that, among middle and high school female patients with patellofemoral pain, a potential association exists between the development of patellofemoral pain and a subsequent risk of developing ACL injuries later in adolescence. This observation is made in the context of a youth sporting environment that has seen a rapid increase in the incidence of pediatric and adolescent ACL injuries. The increased rate of ACL injury in the young age group has been attributed to early, single sport specialization coupled with a demand for peak performance during a time of change, particularly physiologically, when neuromuscular control and physical fitness may be lacking.
Emotional
Although there is a tendency to concentrate on the physical manifestations of specialization, the psychosocial factors play as important, if not more important, role. Malina described social isolation, overdependence, and burnout as potential consequences ( Box 2 ).
History
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Decreased performance despite weeks to months of recovery
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Mood disturbances
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Lack of enjoyment in sport
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Presence of triggers such as high training volumes, high time demands, monotony of training, excessive number of competitions.
Physical Examination
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Muscle tightness (positive Ober test, positive Thomas test, popliteal angle >25, ankle dorsiflexion <5, glenohumeral internal rotation deficit)
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Ligamentous laxity
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Q angle greater than 20
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Valgus knee collapse on single leg squat test
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