Overuse Injuries and Burnout in Youth Sports

Abstract

Executive Summary BACKGROUND Youth sport participation offers many benefits including the development of self-esteem, peer socialization, and general fitness. However, an emphasis on competitive success, often driven by goals of elite-level travel team selection, collegiate scholarships, Olympic and National team membership, and even professional contracts, has seemingly become widespread. This has resulted in increased pressure to begin high-intensity training at young ages. Such an excessive focus on early intensive training and competition at young ages rather than skill development can lead to overuse injury and burnout. PURPOSE To provide a systematic, evidenced-based review that will: ∘ Assist clinicians in recognizing young athletes at risk for overuse injuries and burnout. ∘ Delineate the risk factors and injuries that are unique to the skeletally immature young athlete. ∘ Describe specific high-risk overuse injuries that present management challenges and/or can lead to long-term health consequences. ∘ Summarize the risk factors and symptoms associated with burnout in young athletes. ∘ Provide recommendations on overuse injury prevention. METHODOLOGY Medical Subject Headings (MeSHs) and text words were searched on March 26, 2012, for MEDLINE, CINAHL, and PsychINFO. Nine hundred fifty-three unique articles were initially identified. Additional articles were found using cross-referencing. The process was repeated July 10, 2013, to review any new articles since the original search. Screening by the authors yielded a total of 208 relevant sources that were used for this paper. Recommendations were classified using the Strength of Recommendation Taxonomy (SORT) grading system. DEFINITION OF OVERUSE INJURY Overuse injuries occur due to repetitive submaximal loading of the musculoskeletal system when rest is not adequate to allow for structural adaptation to take place. Injury can involve the muscle-tendon unit, bone, bursa, neurovascular structures, and the physis. Overuse injuries unique to young athletes include apophyseal injuries and physeal stress injuries. EPIDEMIOLOGY It is estimated that 27 million US youth between 6 to 18 years of age participate in team sports. The National Council of Youth Sports survey found that 60 million children aged 6 to 18 years participate in some form of organized athletics, with 44 million participating in more than 1 sport. There is very little research specifically on the incidence and prevalence of overuse injuries in children and adolescents. Overall estimates of overuse injuries versus acute injuries range from 45.9% to 54%. The prevalence of overuse injury varies by the specific sport, ranging from 37% (skiing and handball) to 68% (running). Overuse injuries are underestimated in the literature because most epidemiologic studies define injury as requiring time loss from participation. RISK FACTORS Prior injury is a strong predictor of future overuse injury. Overuse injuries may be more likely to occur during the adolescent growth spurt. ∘ The physes, apophyses, and articular surfaces in skeletally immature athletes in a rapid phase of growth are less resistant to tensile, shear, and compressive forces than either mature bone or more immature prepubescent bone. ∘ A decrease in age-adjusted bone mineral density that occurs before peak height velocity may also play a role. ∘ Other factors that may contribute are a relative lack of lean tissue mass, an increase in joint hypermobility, and imbalances in growth and strength. ∘ Physeal stress injuries appear to be more common during rapid growth and may be related to a period of vulnerability of metaphyseal perfusion. There is little evidence to support a causal relationship between overuse injury and anatomic malalignment or flexibility. A history of amenorrhea is a significant risk factor for stress fractures. Higher training volumes have consistently been shown to increase the risk of overuse injury in multiple sports. Other factors that may contribute to overuse injury but lack clinical data include: ∘ Poor-fitting equipment, particularly when not adjusted for changes in growth. ∘ Overscheduling, such as multiple competitive events in the same day or over several consecutive days. This factor may be better considered as a marker for a high ratio of workload-to-recovery time. READINESS FOR SPORTS Readiness for sports is related to the match between a child's level of growth and development (motor, sensory, cognitive, social/emotional) and the tasks/demands of the competitive sport. Chronological age is not a good indicator on which to base sport developmental models because motor, cognitive, and social skills progress at different rates, independent of age. Coaches and parents may lack knowledge about normal development and signs of readiness for certain tasks, both physically and psychosocially. ∘ This can result in unrealistic expectations that cause children and adolescents to feel as if they are not making progress in their sport. ∘ Consequently, children may lose self-esteem and withdraw from the sport. SPORT SPECIALIZATION Sport specialization may be considered as intensive, year-round training in a single sport at the exclusion of other sports. There is concern that early sport specialization may increase rates of overuse injury and sport burnout, but this relationship has yet to be demonstrated. Diversified sports training during early and middle adolescence may be more effective in developing elite-level skills in the primary sport due to skill transfer. HIGH-RISK OVERUSE INJURIES “High-risk” overuse injuries are those that can result in significant loss of time from sport and/or threaten future sport participation. These include certain stress fractures, physeal stress injuries, osteochondritis dissecans, some apophyseal injuries, and effort thrombosis. High-risk stress fractures include: ∘ The pars interarticularis of the spine, the tension side of the femoral neck, the patella, the anterior tibia (the “dreaded black line”), the medial malleolus, the talus, the tarsal navicular, the metaphyseal/diaphyseal junction of the fifth metatarsal (Jones fracture) and the sesamoids. ∘ A high index of suspicion should be maintained for athletes complaining of pain at the sites of potential high-risk bone stress injuries including the central lumbar spine, anterior hip, groin or thigh, anterior knee, anterior leg, medial ankle, dorsal/medial midfoot, lateral foot, and plantar aspect of the great toe. Physeal stress injuries can occur at the proximal humerus, distal radius, distal femur, and the proximal tibia. ∘ Although most physeal stress injuries resolve with rest, some may result in growth disturbance and joint deformity. Effort thrombosis in athletes occurs as a consequence of thoracic outlet syndrome. ∘ A significant percentage of upper extremity effort thrombosis happens in adolescents as result of overuse. ∘ First rib resection frequently results in a successful return to full activity. ∘ All cases should undergo evaluation for an underlying coagulopathy. BURNOUT Burnout is part of a spectrum of conditions that includes overreaching and overtraining. It has been defined to occur as a result of chronic stress that causes a young athlete to cease participation in a previously enjoyable activity. Sport specialization may be a factor. ∘ Data suggest that athletes who had early specialized training withdrew from their sport either due to injury or burnout from the sport. However, not all young athletes who drop out of sports are burned out. ∘ Most youth who discontinue a sport do so as a result of time conflicts and interest in other activities. ∘ Some may reenter the same sport or participate in a different sport in the future. In children there appears to be more of a psychological component related to burnout and attrition with adult supervised activities. PREVENTION Limiting weekly and yearly participation time, limits on sport-specific repetitive movements (eg, pitching limits), and scheduled rest periods are recommended. (B) Such modifications need to be individualized based upon the sport and the athlete's age, growth rate, readiness, and injury history. (C) Careful monitoring of training workload during the adolescent growth spurt is recommended, as injury risk seems to be greater during this phase. (B) This apparent increased risk may be related to a number of factors including diminished size-adjusted bone mineral density, asynchronous growth patterns, relative weakness of growth cartilage, and physeal vascular susceptibility. Preseason conditioning programs can reduce injury rates in young athletes. (B) Prepractice neuromuscular training can reduce lower extremity injuries. (B) Given the altered biomechanics that may occur with ill-fitting equipment, proper sizing and resizing of equipment is recommended, although data are lacking that demonstrate a link to injury. (C) To reduce the likelihood of burnout, an emphasis should be placed on skill development more than competition and winning. (C) SUMMARY FINDINGS AND RECOMMENDATIONS Overuse injuries are underreported in the current literature because most injury definitions have focused on time loss from sport. (B) Preparticipation exams may identify prior injury patterns and provide an opportunity to assess sport readiness. (C) A history of prior injury is an established risk factor for overuse injuries that should be noted as part of each injury assessment. (A) Adolescent female athletes should be assessed for menstrual dysfunction as a predisposing factor to overuse injury. (B) Parents and coaches should be educated regarding the concept of sport readiness. (C) Variations in cognitive development, as well as motor skills, should be considered when setting goals and expectations. Early sport specialization may not lead to long-term success in sports and may increase risk for overuse injury and burnout. (C) With the possible exception of early entry sports such as gymnastics, figure skating, and swimming/diving, sport diversification should be encouraged at younger ages. When an overuse injury is diagnosed, it is essential to address the underlying cause(s). (C) The athlete, parents, and coaches should be involved in reviewing all risk factors and developing a strategy to attempt to avoid recurrent injury. All overuse injuries are not inherently benign. (A) Clinicians should be familiar with specific high-risk injuries, including stress fractures of the femoral neck, tarsal navicular, anterior tibial cortex and physis, and effort thrombosis. BACKGROUND AND PURPOSE Participation in youth sports can be an enjoyable experience for children and adolescents with many potential benefits. It offers opportunities for peer socialization, the development of self-esteem and leadership qualities, and also promotes health and fitness. However, the increasing highly competitive nature of youth sports has fueled trends of extensive training, sport specialization, and participation in large numbers of competitive events at young ages. Consequently, overuse injuries and burnout have become common. This report will review what is currently known about the epidemiology and risk factors associated with overuse injuries and burnout in young athletes. It will highlight specific overuse injuries that may pose management challenges or lead to long-term consequences. Recommendations for prevention will also be presented. INTRODUCTION The number of participants in youth sports is difficult to determine. The National Federation of State High School Associations reported that 7 713 577 student athletes (4 490 854 male, 3 222 723 female) participated in 2012–2013.1 However, this represents only a fraction of all participants at any level. Estimates for younger athletes and/or those in nonscholastic sports may best be projected from data obtained by national sport organizations. One recent survey found that approximately 27 million children and adolescents between the age of 6 and 17 years participate regularly in team sports in the United States.2 Among specific youth sport organizations, an estimated 2.3 million children played Little League baseball, over 600 000 participate in the America Youth Soccer Organization and 365 000 play softball.3,4 The 2008 National Council of Youth Sports survey found that approximately 60 million children aged 6 to 18 years participate in some form of organized athletics.5 Of these, approximately 44 million participated in more than 1 sport.5 In addition, although there is a paucity of data describing the extent of youth sport participation, it is clear that large numbers of children do not limit their sports to a given “season” and are involved throughout the calendar year in organized athletics. An emphasis on competitive success has become widespread, resulting in increased pressure to begin high-intensity training at young ages. This may be driven by parental goals of having their child selected for high-level travel teams, collegiate scholarships, and even professional contracts. Alternatively, the initiative may originate with the child or be fostered by coaches or peers. In pursuit of athletic success, children and their parents may enlist the services of a personal sport coach and/or fitness instructor, and also register for camps and showcase events. Some parents or coaches may encourage a child to concentrate on a single sport in an attempt to improve his or her chances of elite team selection, and therefore exposure to the college recruiting process. Children may also play on more than 1 team or participate in more than 1 sport at a given time. It is also important to recognize that children's sports are a big business.6 Coaches, personal trainers, club team organizations, sporting goods manufactures, tournament directors, and others have a financial stake in youth sports participation. Given this trend toward early and multifaceted training, frequent competition, and single sport specialization, it is no surprise that overuse injuries and burnout are common. This paper will describe several issues related to the development of overuse injury and burnout. Particular attention will be placed on the unique factors surrounding growth and development that deserve special consideration in young athletes. By understanding these issues, clinicians will better be able to treat these injuries, educate parents, athletes and coaches, and provide recommendations for injury prevention. METHODOLOGY Data Sources Three electronic databases were searched on March 26, 2012, to identify potentially relevant articles: MEDLINE, CINAHL, and PsychINFO. A combination of Medical Subject Headings (MeSHs) and text words were used in this search (Table 1). A total of 953 unique articles were identified. Additional articles and related information were found using cross-referencing and the authors' personal libraries. The articles were screened by title and by abstract. Those felt to be relevant to this document were reviewed in full by the authors. The process was repeated July 10, 2013, to review any new articles since the initial search was performed. A total of 208 unique references were ultimately chosen for this paper.TABLE 1: Search MethodologyDefinition of Overuse Injury Although there is no clear consensus on the definition of overuse injury, it is generally recognized that overuse injuries occur due to repetitive submaximal loading of the musculoskeletal system when rest is not adequate to allow for structural adaptation to take place.7–10 Such injury may involve the muscle-tendon unit, bone, articular cartilage, physis, bursa, and/or neurovascular structures. During sport participation, repetitive loading to these structures results in microtrauma. When recovery between loading exposures is sufficient, tissue adaptation occurs to accommodate the imposed stress. However, excessive stress and/or an inadequate recovery period can overwhelm the ability of the tissue to remodel, resulting in a weakened, damaged structure. This imbalance between training loads and recovery is a key factor, perhaps even more so in young athletes with an immature musculoskeletal system. Because of ongoing growth and development, the types of overuse injuries that occur in young athletes differ compared to adults.11,12 Specifically, growth-related conditions such as apophysitis and physeal stress injury are unique to young athletes.13–15 Apophyseal injuries typically occur in early adolescence. The most common sites involve the tibia tubercle of the knee (Osgood-Schlatter disease), the calcaneal apophyisis of the heel (Sever's disease), and the medial epicondylar apophysis of the elbow (often referred to as Little Leaguer's Elbow). Anterior knee pain is one of the most frequent complaints in the young athlete.16 In early adolescence this is usually due to Osgood-Schlatter disease, while in later adolescence the tibial tubercle apophysis matures, and patellofemoral pain syndrome (PFPS) becomes the more common cause of knee pain. Overuse injuries of the physis (eg, proximal humerus in throwers, distal radius in gymnasts) occur in early to mid-adolescence.14,17–19 As skeletal maturity is achieved, overuse injuries to bone begin to follow adult injury patterns (eg, stress reactions and stress fractures). EPIDEMIOLOGY OF OVERUSE INJURIES Overall, there is very little research specifically on the incidence and prevalence of overuse injuries in children and adolescents.20–24 Furthermore, studies of sports injuries in youth are limited by several issues including injury reporting methodology, injury classification, and standardization of outcomes. In particular, injury definitions that require time loss from sport underestimate the burden of overuse injuries.9,25 A recent study of 100 US high schools reported that the overall injury rate (acute and overuse) in 20 high school sports was 1.71/1000 athlete exposures (AEs) during the 2010–2011 school year.23 This database estimates 3.7 million injuries occurred that resulted in more than 1 day's time loss from sports. This estimate does not include injuries seen outside of the high school setting. Importantly, this study further underestimates injury rates since it does not account for injuries which did not result in time loss, as is the case in many overuse injuries.9 Another data source, the National SAFE KIDS Campaign, estimates that more than 3.5 million children are injured annually playing sports or participating in recreational activities.22 Estimates of the proportion of all sports injuries that are due to overuse range from 45.9% to 54%.7,24,26 Although evidence is sparse, there is concern that these injuries are increasing.27–29 The frequency and type of overuse injuries in elite young athletes varies by sport and by age.30 Sport-related training and conditioning are also factors (eg, resistance training as an adjunct to soccer training).30 Overuse, noncontact injuries in American football are 2.6 times more likely to occur at the college level than high school.31 In a recent 3-year study of 16 sports at 1 university, 29.3% of injuries were considered overuse injuries.9 Baxter-Jones et al studied 453 elite young athletes in 4 sports (231 boys, 22 girls; 8–16 years of age) and found that the prevalence of overuse injuries varied by sport: 63% for swimmers, 33% for gymnasts and tennis players, and 15% for soccer players.30 Other studies report the prevalence of overuse injury among different youth sports to range from 37% (skiing and handball) to 68% (running).32–34 RISK FACTORS FOR OVERUSE INJURIES A variety of factors have been proposed to contribute to overuse injuries. They are often grouped into either intrinsic or extrinsic factors (Table 2). Intrinsic factors are defined as individual biological characteristics and psychosocial traits. Extrinsic factors refer to external forces related to the sport type, the biomechanics of the activity, and the sporting environment.35 Commonly cited intrinsic factors include variations in growth and development, anatomic alignment, muscle-tendon imbalance, flexibility, conditioning, biomechanics, and a history of prior injury. Extrinsic factors include workload, sport technique, training environment, and equipment. The contribution of an intrinsic or an extrinsic factor to injury risk is extremely variable depending on the individual athlete, the sport environment, and the interaction that occurs during participation.35–37 Furthermore, it is important to recognize that many overuse injuries result from a complex interaction of multiple risk factors in specific settings coupled with an inciting event. Understanding this concept is necessary for the comprehensive evaluation and treatment of athletes with overuse injuries.38,39TABLE 2: Categorization of Risk Factors for Overuse InjuryIt is also relevant to note that some risk factors are modifiable (eg, strength, neuromuscular function), whereas others are not (eg, age, gender).38 Finally, in young athletes, characteristics of the developing musculoskeletal system are especially important to consider. Although little data exist that identifies a causal relationship between proposed risk factors and overuse injury, recognizing these potential contributors to injury is important in limiting recurrent injury and in developing injury prevention strategies.15,37,40 Intrinsic Risk Factors Prior Injury Previous injury is the strongest predictor of future injuries.41–50 Repeated overuse injury may occur as a result of inadequate rehabilitation of the index injury and/or a failure to recognize and correct the factors that contributed to the original injury. Growth and Development Children undergo growth and development at an individual rate. Biologic growth and maturation are primarily genetically regulated; development is more culturally mediated.36,51 For example, the development of child's play paradigms can vary depending on the cultural exposure to solitary play, parallel play, associate play, and cooperative play situations.52 Physical growth and cognitive development both influence successful participation in sports. Overall body mass and height increase in the pre-adolescent and adolescent years.53 Girls tend to reach their peak height and body mass at approximately age 15, whereas boys may experience increases beyond age 18. Maturation is a complex process that encompasses skeletal, somatic, and sexual maturation. Each component of maturation occurs at an independent, sometimes asynchronous, rate in an individual. Although wide variations in the maturation rates have been suggested to increase injury risk, data demonstrating a definitive link between discordant maturation and injury are lacking.54,55 Overuse injuries may be more common during the adolescent growth spurt. Laboratory studies demonstrate that the growth cartilage present at the physes, apophyses, and articular surfaces in skeletally immature athletes in a rapid phase of growth are less resistant to tensile, shear, and compressive forces than either mature bone or more immature prepubescent bone.56–58 Acute distal radius fractures peak during and just before peak height velocity.59,60 Stress fractures, distal radial physeal stress injuries, and low back pain also appear to occur with a greater prevalence during the adolescent growth spurt.61–63 Prospective studies are needed to further evaluate this relationship. A decrease in age-adjusted bone mineral density that occurs before peak height velocity may also play a role.64 A relationship to acute traumatic fractures has been demonstrated, but its role in overuse injury has not yet been determined. In addition, dissociation is seen between bone matrix formation and the occurrence of bone mineralization during the growth spurt resulting in relatively diminished bone strength.64,65 Other factors that may contribute are a relative lack of lean tissue mass, an increase in joint hypermobility, and imbalances in growth and strength.66–69 Longitudinal growth of extremities results in changes in length, mass, and stress forces on bone-tendon junctions, muscle-tendon junctions, growth cartilage, and ligaments that frequently occur asynchronously.69 These imbalances in growth and strength, coupled with repetitive loading, appear related to increased injury risk, although the exact relationship is not clearly delineated and is likely multifactorial. Overuse injuries of the physis may be due to diminished perfusion related to excessive mechanical loading. Magnetic resonance imaging (MRI) of physeal stress injuries of the distal radius in young gymnasts shows an appearance similar to experimentally induced injuries in which metaphyseal artery perfusion has been disrupted.55,70–72 This injury is significantly more likely to occur in gymnasts who are within the expected age range of the adolescent growth spurt.19,61 Anatomic Alignment Alignment abnormalities such as patellofemoral malalignment, pes planus, pes cavus, elbow hyperextension, and excessive lumbar lordosis are some of the more commonly cited risk factors for overuse injuries.21,73–75 Joint hypermobility has also been associated with injury in some studies.76,77 Accurate assessment of these factors, including measuring both static and dynamic components, is difficult to achieve in the office setting. In addition, defining a cause and effect relationship between these characteristics and injury has been elusive.78,79 Recent studies have not established consistent predictors. Given the broad diversity of sport-specific demands placed on the body, considerably more information is needed to formulate models whereby anatomic alignment may predict injury risk.73,80,81 Overall, the significance of osseous alignment abnormalities versus soft tissue alignment abnormalities in relation to injury is complex, poorly understood, and likely sport specific. Alignment can be altered through use of supportive equipment. The use of custom shoe orthotics to alter alignment, particularly in runners, is controversial, yet widely used. The use of an orthotic can have both a short- and a long-term effect on lower extremity kinematics such as rearfoot eversion angles, velocity, impact peak, and loading rate, as well as knee kinematics. However, the clinical significance of this with regard to effects on injury rates remains unknown.82 There is also the potential to increase injury risk depending on the effect of the altered kinematics on sport participation. Flexibility A causal relationship between flexibility and injury risk has not been documented. Early reviews proposed that inflexibility across the muscle-tendon unit develops during the adolescent growth spurt that may contribute to injury.83 However, several recent studies have not shown any relationship between growth and inflexibility in boys or girls.84–86 Studies investigating the role of pre-exercise stretching on injury risk have shown mixed results.87,88 Interventions that consider age, gender, and specific sports are needed. Biomechanics Limb length, body mass, and moments of inertia change rapidly during the adolescent growth spurt, and all can affect coordination and movement patterns.53,66,69 This is likely due to the need for greater force generation for extremity movement during a time when strength and coordination are still developing. This may play a role in the increased risk for injury seen during the growth spurt.35,36,55–63 Structural or dynamic disturbances in extremity mechanics appear to increase eccentric loads.69,89 These findings can then serve as the basis for targeted rehabilitation programs that emphasize improvement in sport-specific biomechanics.89,90 In some cases, it is not clear if sport-related changes in joint range of motion play a role in overuse injury or reflect a positive biomechanical adaptation.91,92 In overhead athletes, a decrease in dominant arm internal rotation coupled with greater strength in internal rotators is typically seen relative to the nondominant arm.91 One laboratory study in Peewee ice hockey players performing a sprint start displayed “at risk” hip kinematics including internal hip rotation during flexion or “push-off” phase and external rotation during abduction or recovery phase, thus placing the hip in a position to potentially cause femoroacetabular impingement and/or labral stress.93 These studies suggest sport-specific kinematic profiles deserve further investigation to determine if such factors predispose to overuse injury. Strength and Conditioning Benefits of youth fitness include those related to cardiovascular health, bone health, and mental health.94–96 Among young athletes, general activity and fitness levels vary greatly. Children who have not developed some foundation of general strength, endurance, and motor skills may be at increased risk for injury, although little data exist at this time. Some potential risk factors that are modifiable include poor endurance and lack of preseason preparation.97–101 Menstrual Irregularity and Low Energy Availability A history of amenorrhea, especially in sports that emphasize leanness, is a risk factor for bone stress injury. One study in collegiate female distance runners found a linear relationship between number of menses per year and risk of stress fracture, with amenorrheic runners having the highest risk.102 Several studies have suggested that a history of amenorrhea is a significant risk factor for stress fractures.99,101–105 The proposed mechanism correlates inadequate caloric intake with hypoestrogenemia, decreased bone density, and subsequent increased fracture risk.106,107 The relationship between oral contraceptive use and the likelihood of stress fracture is not well understood.108 The studies cited generally focused on young women and older adolescents. There is little data regarding menstrual irregula