Movement Regularity Differentiates Specialized and Nonspecialized Athletes in a Virtual Reality Soccer Header Task.

BACKGROUND: Young athletes who specialize early in a single sport may subsequently be at increased risk of injury. While heightened injury risk has been theorized to be related to volume or length of exposure to a single sport, the development of unhealthy, homogenous movement patterns, and rigid neuromuscular control strategies may also be indicted. Unfortunately, traditional laboratory assessments have limited capability to expose such deficits due to the simplistic and constrained nature of laboratory measurement techniques and analyses. METHODS: To overcome limitations of prior studies, the authors proposed a soccer-specific virtual reality header assessment to characterize the generalized movement regularity of 44 young female athletes relative to their degree of sport specialization (high vs low). Participants also completed a traditional drop vertical jump assessment. RESULTS: During the virtual reality header assessment, significant differences in center of gravity sample entropy (a measure of movement regularity) were present between specialized (center of gravity sample entropy: mean = 0.08, SD = 0.02) and nonspecialized center of gravity sample entropy: mean = 0.10, SD = 0.03) groups. Specifically, specialized athletes exhibited more regular movement patterns during the soccer header than the nonspecialized athletes. However, no significant between-group differences were observed when comparing participants' center of gravity time series data from the drop vertical jump assessment. CONCLUSIONS: This pattern of altered movement strategy indicates that realistic, sport-specific virtual reality assessments may be uniquely beneficial in exposing overly rigid movement patterns of individuals who engage in repeated sport specialized practice.

Differences in career longevity before and after implementation of the Women's Tennis Association Tour Age Eligibility Rule and Player Development Programmes: a 25-year study.

OBJECTIVES: To assess differences in career longevity, as a potential marker of athlete well-being, before and after the 1995 implementation of the Women's Tennis Association (WTA) Age Eligibility Rule (AER) and Player Development Programmes (PDP), which focused on organisational, physical and psychosocial education, skill building and support for adolescent athletes (≤17 years). METHODS: Career longevity data were collected through 2019 on adolescent players who began professional tournament play between 1970 and 2014 and reached a WTA singles ranking of 1-150 for a minimum of 1 week during their careers. Players were separated into pre-AER/PDP and post-AER/PDP groups, consisting of those who played their first professional events (FPE) before or after 1 January 1995. Measures of career longevity included career duration and premature retirement. RESULTS: Eight-hundred and eleven players were included in this study (51% pre-AER/PDP). The median career duration was 14.2 years for the post-AER/PDP group compared with 12.1 years for the pre-AER/PDP group (p<0.001). Moreover, post-AER/PDP players had higher probabilities of 10-year and 15-year careers compared with pre-AER/PDP players. After adjusting for age at FPE, athletes in the pre-AER/PDP group had an increased risk of shorter career duration (HR 1.55; 95% CI 1.31 to 1.83) and increased odds of premature retirement (OR 5.39; 95% CI 2.28 to 12.75) than athletes in the post-AER/PDP group. CONCLUSIONS: Adolescent athletes participating on the WTA after the combined AER/PDP initiative had longer career durations, higher probabilities of 10-year and 15-year careers, and decreased risk of premature retirement compared with those participating prior to AER/PDP. Organisational practices that encompass both education and competition regulation can positively affect career longevity related to improving athlete well-being.

Current Sport Organization Guidelines From the AMSSM 2019 Youth Early Sport Specialization Research Summit.

CONTEXT: Youth athletes may be at elevated risk for adverse health due to sport specialization. Sport organizations have developed guidelines for participation during growth and development. OBJECTIVE: To assess youth sport development guidelines using a 15-item framework across sport organizations and governing bodies in soccer, basketball, ice hockey, and swimming. DATA SOURCES: English-language results from January 1, 2000, to December 31, 2018, from published sport organization guidelines and athlete development plans. STUDY SELECTION: Two investigators independently reviewed publications identified from sport organizations. A total of 23 guidelines were incorporated, including 5 general sport organizations and 18 sport-specific guidelines. STUDY DESIGN: Systematic review. LEVEL OF EVIDENCE: Level 4. DATA EXTRACTION: Two investigators independently identified all recommendations that fit within a predetermined rubric of recommendations encompassing 4 domains: Psychological Development/Approach, Physical Development/Load, Facilities and Resources, and Timing and Monitoring of Specialization. Sport-specific guidelines on volume were summarized. RESULTS: Sport organizations and sport-specific guidelines had consensus on 2 items out of the 15-item: emphasis on early skill development and access to well-trained coaches. While recommended by all sports organization, multisport participation was emphasized by 3 of 4 sports, excluding soccer. Volume recommendations were inconsistent between and within sports. No group proposed methods to monitor athlete well-being. CONCLUSION: This review highlights areas of agreement within sport organizations and governing bodies. Creating a framework to guide youth sport specialization may lead to specific and consistent guidelines.

Systematic Review of Health Organization Guidelines Following the AMSSM 2019 Youth Early Sport Specialization Summit.

CONTEXT: Youth sport specialization may place young athletes at increased risk for negative impacts to their physical and/or psychological health. In response to these health concerns, several health organizations have created guidelines and position statements to guide parents and practitioners toward best practices for management of the young athlete. OBJECTIVE: To systematically review and synthesize current organizations' recommendations and guidelines regarding youth sport specialization. DATA SOURCES: English-language articles from January 1, 2000, to December 31, 2018, in the NCBI Pubmed, Embase, Cochrane, CINAHL, and SPORTDiscus databases. STUDY SELECTION: Articles that reported on recommendations or interventions by health organizations or health representatives of sports organizations. A total of 56 articles were assessed, with 11 meeting inclusion eligibility criteria. STUDY DESIGN: Systematic review. LEVEL OF EVIDENCE: Level 4. DATA EXTRACTION: Two investigators independently identified all recommendations within the results that fit within a 15-item framework encompassing 4 domains: Psychological Development/Approach, Physical Development/Load, Facilities and Resources, and Timing and Monitoring of Specialization. RESULTS: Recommendations across organizations were primarily clustered in the Physical Development/Load (43%), Facilities and Resources (48%), and Sport Specialization (55%) domains. In contrast, the Psychological Development/Approach domain had fewer recommendations (20%). The most common recommendations endorsed concepts: "Monitor athlete well-being," "Youth athletes need access to well-trained, quality coaches," "Multi-sport participation," "Limit early organized participation and/or training," and "Parents require awareness of training, coaching, and best practices." The level of evidence provided to support a given recommendation varied significantly. The level of detail and the consistency of terms used throughout the results were typically low. Recommendations were frequently made without reference to potential outcome measures or specific strategies that could be used for practical implementation in the community. CONCLUSION: There was broad representation of different aspects of specialization but limited consistency between health organization guidelines. Adopting a framework for recommendations as used in this review could assist organizations in structuring future recommendations that are specific, measurable, and framed in a manner that will promote action in the youth sport community.

Editorial Commentary: Considering Fatigue When Assessing Athletes for Dynamic Knee Valgus: Is This the Next Big Step in Identifying Anterior Cruciate Ligament Injury Risk?

Excessive dynamic knee valgus during jumping is a poor movement strategy that has been well-documented as a risk factor for anterior cruciate ligament injury. Yet, there has been little progress in the translation of findings from high-tech motion capture laboratories to clinically applicable settings. One barrier to widespread use is expensive technology that requires time; therefore, field-based efficient assessment tools that can be used by several types of clinicians are desperately needed. Further, fatigue can influence dynamic knee valgus and should be considered when assessing or conditioning athletes.

Sport Specialization and Coordination Differences in Multisport Adolescent Female Basketball, Soccer, and Volleyball Athletes.

CONTEXT: Early sport specialization, or the participation in 1 sport year-round to the exclusion of all others, is a growing concern in youth athletics because of its possible association with musculoskeletal injury. The underlying injury risk may be the result of coordination differences that sport-specialized athletes have been speculated to exhibit relative to multisport athletes; however, little evidence exists to support or refute this notion. OBJECTIVE: To examine relative hip- and knee-joint angular-motion variability among adolescent sport-specialized and multisport female adolescent athletes to determine how sport specialization may affect coordination. DESIGN: Cohort study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 366 sport-specialized and 366 multisport adolescent female basketball, soccer, and volleyball players. INTERVENTION(S): Drop-vertical-jump (DVJ) assessment. MAIN OUTCOME MEASURE(S): Average coupling-angle variability (CAV) for hip flexion and knee flexion, knee flexion and ankle flexion, hip flexion and knee abduction, knee flexion and knee abduction, knee flexion and knee internal rotation, and knee abduction and knee internal rotation. RESULTS: The sport-specialized group exhibited increased coupling variability in dominant-limb hip flexion and knee flexion (P = .015), knee flexion and knee abduction (P = .014), and knee flexion and knee internal rotation (P = .048) while landing during the DVJ, although they had small effect sizes (η2 = 0.010, 0.010, and 0.007, respectively). No differences were present between groups for any of the other CAV measures of the dominant limb, and no differences were found for any CAV measures of the nondominant limb (all P values > .05). CONCLUSIONS: Sport specialization was associated with increased variability of critical hip- and knee-joint couplings responsible for effective landing during the DVJ. Altered coordination strategies that involve the hip and knee joints may underlie unstable landings, inefficient force-absorption strategies, or greater contact forces that can place the lower extremities at risk for injury (or a combination of these).

Health Consequences of Youth Sport Specialization.

Sport specialization is a training method now commonly used by young athletes who hope to achieve elite-level success. This may be defined as (1) choosing a main sport, (2) quitting all other sports to focus on 1 sport, and (3) year-round training (greater than 8 months per year). A number of sports medicine organizations have published recommendations based on the limited evidence available on this topic. The objective of this article was to perform a narrative review of the currently available evidence and sports medicine organizational recommendations regarding sport specialization and its effects on health to guide athletic trainers and sports medicine providers. To accomplish this goal, we conducted a narrative review of articles and position statements on sport specialization published from 1990 through 2018. Injury, overuse injury, serious overuse injury, and lower extremity injury were likely associated with higher degrees of sport specialization in various populations. Sports medicine organizations in general recommended against sport specialization in young athletes and instead promoted multisport participation for physical and psychological benefits. Few long-term data suggest that sport specialization has negative health-related quality-of-life consequences. Higher degrees of sport specialization likely pose risks of overuse injury; however, the age of specialization at which this risk occurs is not known. Because different populations and sports activities may put children at risk for certain injuries, future researchers should monitor large populations with sport-specific prospective active surveillance.

Lower Extremity Biomechanics Are Altered Across Maturation in Sport-Specialized Female Adolescent Athletes.

Sport specialization is a growing trend in youth athletes and may contribute to increased injury risk. The neuromuscular deficits that often manifest during maturation in young, female athletes may be exacerbated in athletes who specialize in a single sport. The purpose of this study was to investigate if sport specialization is associated with increased lower extremity biomechanical deficits pre- to post-puberty in adolescent female athletes. Seventy-nine sport-specialized female adolescent (Mean ± SD age = 13.4 ± 1.8 years) basketball, soccer, and volleyball athletes were identified and matched with seventy-nine multi-sport (soccer, basketball, and volleyball) female athletes from a database of 1,116 female adolescent basketball, soccer, and volleyball athletes who were enrolled in one of two large prospective, longitudinal studies. The athletes were assessed over two visits (Mean ± SD time = 724.5 ± 388.7 days) in which they were classified as pre-pubertal and post-pubertal, respectively. Separate 2 × 2 analyses of covariance were used to compare sport-specialized and multi-sport groups and dominant/non-dominant limbs with respect to pubertal changes in peak knee sagittal, frontal, and transverse plane joint angular measures and moments of force recorded while performing a drop vertical jump task. The sport-specialized group were found to exhibit significantly larger post-pubertal increases in peak knee abduction angle (p = 0.005) and knee abduction moment (p = 0.006), as well as a smaller increase in peak knee extensor moment (p = 0.032) during landing when compared to the multi-sport group. These biomechanical changes are indicative of potentially compromised neuromuscular control that may increase injury risk pre- to post-puberty in sport-specialized female athletes. Consideration of maturation status may be an important factor in assessing the injury risk profiles of adolescent athletes who specialize in sport.

Socioeconomic Factors for Sports Specialization and Injury in Youth Athletes.

BACKGROUND: The effect of socioeconomic status (SES) on rates of sports specialization and injury among youth athletes has not been described previously. HYPOTHESIS: Young athletes from lower socioeconomic status will have lower rates of sports specialization and subsequently lower risk of overuse injuries. STUDY DESIGN: Cohort study. LEVEL OF EVIDENCE: Level 3. METHODS: Injured athletes aged 7 to 18 years were recruited from 2 hospital-based sports medicine clinics and compared with uninjured athletes presenting for sports physicals at primary care clinics between 2010 and 2013. Participants completed surveys on training patterns. Electronic medical records provided injury details as well as patient zip code, race, and health insurance type. SES was estimated from zip codes. The sample was divided into SES tertiles. Analysis of variance and multivariate regression were used for continuous variables, and multivariate logistic regression analyses were conducted to explore relationships between risk factors and injury. RESULTS: Of 1190 athletes surveyed, 1139 (96%) had satisfactory SES data. Compared with low-SES athletes, high-SES athletes reported more hours per week spent playing organized sports (11.2 ± 6.0 vs 10.0 ± 6.5; P = 0.02), trained more months per year in their main sport (9.7 ± 3.1 vs 7.6 ± 3.7; P < 0.01), were more often highly specialized (38.9% vs 16.6%; P < 0.01), and had increased participation in individual sports (64.8% vs 40.0%; P < 0.01). The proportion of athletes with a greater than 2:1 ratio of weekly hours in organized sports to free play increased with SES. Accounting for age and weekly organized sports hours, the odds of reporting a serious overuse injury increased with SES (odds ratio, 1.5; P < 0.01). CONCLUSION: High-SES athletes reported more serious overuse injuries than low-SES athletes, potentially due to higher rates of sports specialization, more hours per week playing organized sports, higher ratio of weekly hours in organized sports to free play, and greater participation in individual sports. CLINICAL RELEVANCE: As SES increases, young athletes report higher degrees of sports specialization, greater participation in individual sports, and more serious overuse injuries.

Sports-specialized intensive training and the risk of injury in young athletes: a clinical case-control study.

BACKGROUND: Data are lacking regarding the independent risk of injury related to intense single-sport training or growth rate in young athletes. PURPOSE: To determine whether sports specialization, weekly training volumes, and growth rates are associated with increased risk for injury and serious overuse injury in young athletes. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: Injured athletes aged 7 to 18 years were recruited from 2 hospital-based sports medicine clinics and compared with healthy controls from affiliated primary care clinics undergoing sports physicals (2010-2013). Participants completed surveys reporting hours per week spent in organized sports, physical education class, and free play, as well as degree of sports specialization and Tanner stage. Heights and weights were measured. Injury details were obtained from athlete surveys and electronic medical records. RESULTS: Of 1214 athletes enrolled, 1190 (50.7% male) had data satisfactory for analysis. There were 822 injured participants (49.5% male; unique injuries, n = 846) and 368 uninjured participants (55% male). Injured athletes were older than uninjured athletes (14.1 ± 2.1 vs. 12.9 ± 2.6 years; P < .001) and reported more total hours of physical activity (19.6 ± 9.2 vs. 17.6 ± 8.9 h/wk; P < .001) and organized sports activity (11.2 ± 2.6 vs. 9.1 ± 6.3 h/wk; P < .01). After accounting for age and hours in sports activity spent per week, sports-specialized training was an independent risk for injury (odds ratio [OR], 1.27; 95% CI, 1.07-1.52; P < .01) and serious overuse injury (OR, 1.36; 95% CI, 1.08-1.72; P < .01). Young athletes participating in more hours of sports per week than number of age in years (OR, 2.07; 95% CI, 1.40-3.05; P < .001) or whose ratio of organized sports to free play time was >2:1 hours/week had increased odds of having a serious overuse injury (OR, 1.87; 95% CI, 1.26-2.76; P < .01). Growth rates were similar between injured and uninjured athletes (4.8 cm/y for both groups; P = .96). CONCLUSION: Injured young athletes were older and spent more hours per week in organized sports. There is an independent risk of injury and serious overuse injury in young athletes who specialize in a single sport. Growth rate was not related to injury risk. The study data provide guidance for clinicians counseling young athletes and their parents regarding injury risks associated with sports specialization.

Risk factors for medical withdrawals in United States tennis association junior national tennis tournaments: a descriptive epidemiologic study.

BACKGROUND: There have been no large-scale epidemiologic studies designed to determine the risk factors related to medical withdrawal in United States Tennis Association junior national tennis tournaments. HYPOTHESIS: Risk of medical withdrawal will increase on the basis of cumulative match volume within a tournament. METHODS: A retrospective, cross-sectional analysis was performed of data collected for every match of all 4 United States Tennis Association supernational tournaments (spring, summer, fall, winter) for the boys and girls divisions and for all age divisions (12, 14, 16, 18) during a single year (2005). Logistic regression analysis was performed to determine relative risk of all risk factors. Additional analysis was performed to determine the threshold (ie, match number) at which a player would substantially increase his or her risk of medical withdrawal. RESULTS: A total of 28336 match exposures were analyzed, with an even distribution with respect to sex and age. The total medical withdrawal rate was 15.6 per 1000 match exposures. Every factor of interest was highly significant in predicting a higher rate of medical withdrawal per 1000 match exposures. The medical withdrawal rate was significantly higher in the fifth match or greater (26.3/1000) versus the first 4 matches (12.7/1000; P < .0001), even when analyzing main draw and singles matches. CONCLUSION: In United States Tennis Association national junior tennis tournaments, there is a significant increase in risk of medical withdrawals directly related to older age divisions, boys, singles matches, and main draw matches. Specifically, there is a significant increase in medical withdrawal rate beyond the fourth match in the tournament regardless of whether it is a main draw, consolation, or singles match. CLINICAL RELEVANCE: Recommendations can be made to exercise caution in tournaments that involve boys, older age divisions, and singles. In addition, there may be sufficient evidence to suggest intervention within a tournament when players play beyond their fourth match.