While much is known about the causes and risk factors associated with overuse injuries and burnout, more research is needed, concludes a new position statement from the American Medical Society for Sports Medicine. (DiFiori JP, et al 2014)

"The position statement provides a nice review of the literature that is available," says Jennifer M. Weiss, MD., an orthopedic surgeon with the Southern California Permanente Medical Group at the Los Angeles Medical Center, who was not involved in the preparation of the statement.  

"We do not know how many children and young athletes are affected by overuse injuries. Adolescent girls may be at the highest risk for overuse injuries. Early specialization in sports may put young athletes at risk for overuse injuries, and doesn't necessarily lead to long term success in their sport," says Weiss. 

"If we as parents, coaches, teachers, trainers, and doctors can work together to encourage young athletes to listen to their bodies and to rest and cross-train, we can decrease the phenomenon of overuse injuries and burnout in youth sports."

"If an athlete gets injured or burns out at a young age, they will miss out on the health and emotional benefits associated with sports. It is our job to guide them to work hard but also to rest hard, to vary sporting activity, and to bring any pain that they have to our attention," Weiss says.  

Overuse injuries - causes

• Organized youth sports: Left to themselves, children engaged in spontaneous and unstructured sport and recreational activity are generally free of overuse injury.  It is when adults step into the picture that "injury free" status seems to change. (Roberts WO, 2014)
• Elite-level travel teams: Increased 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 become widespread, resulting in increased pressure to begin high-intensity training at young ages. Excessive focus on early intensive training and competition at young ages rather than skill development can lead to overuse injury and burnout.

Overuse injuries - risk factors

Risk factors for overuse injuries are often grouped into two categories: intrinsic (e.g. individual biological characteristics and psychosocial traits) and extrinsic (e.g. external forces related to the sport type, the biomechanics of the activity, and the sporting environment), some of which are capable of being modified (e.g. strength, neuromuscular function) and others are not (age, gender). 

Intrinsic 

• Prior injury: is the strongest predictor of future overuse injury.  Repeated overuse injury may occur as a result of inadequate rehabilitation of the injury and/or a failure to recognize the factors that contributed to the original injury. 
• Adolescent growth spurt: Overuse injuries may be more common during the adoloscent growth spurt.
• Menstrual irregularity: a history of amenorrhea (irregular periods), especially in sports that emphasize leanness (e.g. gymnastics, figure skating, dance) is a significant risk factor for bone stress injury, although there is little data on younger adolescents.  

 Extrinsic

• Workload: Higher training volumes have consistently been shown to increase the risk of overuse injury in multiple sports. 
  • A study of high school athletes found a linear relationship between hours of sports participation and risk of injury, with training more than 16 hours per week associated with a significant increased risk of injury requiring medical care. 
  • Volume (amount of activity in single session) and intensity (number of sessions per week/month/year) is correlated with overuse injury risk):
    • Number of pitches per game in youth baseball (Parks, 2009; Dun, 2008)
    • More than 100 innings per year (Fleisig G, 2011)
    • Wrist pain in young gymnasts related to training intensity, as measured by skill level and number of hours training per week. (DiFiori, 1996).
• Year-round play.  42% increase in self-reported overuse injuries in high school athletes who participated all year versus 3 or less seasons per year.  (Cuff, 2010).
• More organized sports/less free play.  There is emerging evidence to suggest that athletes who spend most of their time in organized sports and little time in free play or recreation are more likely to be injured. One study (Jayanthi, 2012), for instance, found that the athletes who suffered sport-related injuries spent an average of 12.6 hours per week in tennis and only 2.4 hours per week in free play or recreation, while the uninjured players spent only 9.7 hours per week in organized tennis and 4.3 hours in unstructured free play.

Burnout - risk factors

There are multiple risk factors for young athletes developing overtraining/burnout, experts say, including: 

• Enviromental
  • Extremely high training volumes
  • Extremely high time demands
  • Demanding performance expectations (imposed by self or significant others)
  • Frequent intense competition
  • Inconsistent coaching practices
• Personal characteristics
  • Perfectionism
  • Need to pleases others
  • Nonassertiveness 
  • Unidimensional self-conceptualization (focusing only on one's athletic involvement)
  • Low self-esteem
  • High perception of stress (high anxiety)
• Early specialization: 
  • several studies have suggested that athletes who had early specialized training withdrew from their sport either due to injury or burnout. 
  • A study of swimmers found that those who specialized early spent less time on the national team and retired earlier than those who specialized later
  • Early specialization also seems to be correlated with reports of decreased general health and psychological well-being.

What We Don't Know

• Incidence and prevalence:  Research on overuse injuries in children and adolescents is sparse. Becauses aged-based data is lacking, recommendations for participation and training is often based on extrapolations derived from limited high school and college data, extrapolation which, says one expert (Roberts WO, 2014), is  "fraught with hazard."
• Reasons kids drop out of sports: The issue is complicated issue, with a lack of reliable data hampering informed public opinion and sports polcies.  "Ironically," says one Roberts, the source of the oft-quoted statistic that '80% of youth athletes drop out by age 13' is impossible to find."
• Effect of tournaments and showcases. Despite the absence of data to link these activities with overuse injuries, longer rest periods between matches and games have been proposed in an effort to improve athlete safety and performance, enhance recovery, and minimize the "carryover" effects from previous competitions.  In terms of overuse injuries, scheduling may simply be a marker for a high ratio of workload-to-recovery time. 
• The relationship between sports specialization and injuries. While there are both theoretical and measurable risks associated with intense, specialized training, the relationship has not been clearly demonstrated.  A large study of competitive junior tennis players found that those who competed only in tennis were 1.5 times more likely to have reported an injury, but did not account for training intensity (e.g. weekly training hours). Early data from a clinical study comparing young athletes with sports-related injuries to healthy, uninjured athletes presenting for sports physicals suggests that more specialized athletes were more likely to be injured, but further research, both studies controlling for training intensity and year-round training and evaluating multi-sport athletes over time (e.g. longitudinally) compared to specialized athletes and stages of development to determine the effects of sports diversification with specialization, are needed.  

The path forward

• National research agenda needs to be developed to more carefully examine all aspects of youth sport programs;
• Holistic approach needed which considers how youth sports either contributes to or detracts from the overall health of the child, physical/physiological, psychological, cognitive/academic, social and spiritual;
• Future research needs to focus on age groups (6-10, 11-15, 16-18, 19-25 years); even better, group children by developmental stage (prepubuscent, pubescent, postpubuscent, and late-stage maturation), with different age groupings to account for earlier maturation of girls compared to boys.
• Concerted effort from sports community to develop a funding stream to support research is needed.

"Sports warrant careful and thoughtful stewardship," Roberts concludes. "An understanding of the risks of youth sport participation acquired through careful research, not guessing, will help keep even more kids 'in the game'." 

Sources:

Cuff S, Loud K, O'Riordan MA. Overuse injuries in high school athletes. Clin Pediatr. 2010;49:731-736. 

DiFiori JP, Benjamin HJ, Brenner J, Gregory A, Jayanthi N, Landry GL, Luke A. Overuse Injuries and Burnout in Youth Sports: A Position Statement from the American Medical Society for Sports Medicine. Clin J Sports Med. 2014;24(1):3-20.

DiFiori JP, Puffer JC, Mandelbaum BR, et al. Factors associated with wrist pain in the young gymnast. Am J Sports Med. 1996;24:9-14. 

Dun S, Loftice J, Fleisig GS, et al. A biomechanical comparison of youth baseball pitches: is the curveball potentially harmful? Am J Sports Med. 2008;36:686-692. 

Fleisig GS, Andrews JR, Cutter GR, et al. Risk of serious injury for young baseball pitchers: a 10-year prospective study. Am J Sports Med. 2011;39:253-257. 

Jayanthi N. Injury risks of sport specialization and training in junior tennis players: a clinical study. Paper presented to the Society for Tennis and Medicine Science North American Regional Conference, Atlanta GA. December 2012.

Parks ED, Ray TR. Prevention of overuse injuries in young baseball pitchers. Sports Health. 2009;1:514-517. 

Roberts WO. Overuse Injuries and Burnout in Youth Sports.  Clin J Sports Med. 2014;24(1):1-2.