Parents' Awareness and Perceptions of Sport Specialization and Injury Prevention Recommendations.

OBJECTIVE: To conduct a survey of parents to determine their knowledge of sport volume recommendations and examine their perceptions toward sport specialization. DESIGN: Cross-sectional survey. SETTING: Youth sport athletic tournaments, competitions, and practices. PATIENTS OR OTHER PARTICIPANTS: Parents (n = 1000, 614 women, age: 44.5 ± 6.7 years) of youth athletes completed the survey. Parents had to have a child between 10 and 18 years of age who participated in organized sport in the previous 12 months. INTERVENTIONS: The survey was anonymous and consisted of yes/no and Likert-scale questions and consisted of background of parent and child and perceptions and knowledge of safe sport recommendations. An expert panel validated the survey. MAIN OUTCOME MEASURES: Data were summarized by frequencies, proportions (%), and mean values and SDs, when appropriate. Chi-square analyses were used to determine if parent sex influenced distributions. RESULTS: Over 80% of parents had no knowledge of sport volume recommendations regarding h/wk (84.5%), mo/yr (82.2%), or simultaneous participation in multiple leagues (89.9%). Twenty-four percent of parents considered it appropriate to participate in multiple leagues in the same sport, whereas 60.5% considered it appropriate to participate in multiple leagues of a different sport. Thirty-four percent of parents indicated that they were concerned about the risk of injury in youth sports. Although 55% of parents considered sport specialization a problem in youth sports, only 43.3% thought that year-round sport participation increased the chances of sustaining an overuse injury. Female parents were more likely to be concerned about injury and believe that year-round sport participation results in overuse injury compared with men. CONCLUSIONS: Recommendations associated with youth sport participation are not well known. However, parents are concerned about the risk of injury and consider sport specialization a problem.

Knowledge, Attitudes, and Beliefs of Youth Sports Coaches Regarding Sport Volume Recommendations and Sport Specialization.

Post, EG, Trigsted, SM, Schaefer, DA, Cadmus-Bertram, LA, Watson, AM, McGuine, TA, Brooks, MA, and Bell, DR. Knowledge, attitudes, and beliefs of youth sports coaches regarding sport volume recommendations and sport specialization. J Strength Cond Res 34(10): 2911-2919, 2020-Overuse injuries in youth athletes are becoming increasingly common, which may be a result of the prevalence of year-round specialized sport participation. Previous research has identified sport volume recommendations related to months per year, hours per week, and simultaneous participation in multiple sports leagues. Coaches are a primary influence on a youth athlete's decision to specialize in a single sport. Therefore, identifying coaches' baseline beliefs and perceptions is important for developing strategies to educate coaches about safe sport participation. A total of 253 youth sport coaches (207 males) completed an anonymous online questionnaire regarding knowledge of sport volume recommendations and attitudes and beliefs regarding sport specialization. Eligible participants were required to serve as a head or assistant coach of a youth sport team in the past 12 months whose members were between the ages of 12 and 18 years. Most coaches were unaware of recommendations regarding the maximum number of months per year (79.4%), hours per week in 1 sport (79.3%), or number of simultaneous leagues for an athlete to participate in to reduce injury (77.6%). Fewer than half (43.2%) of all coaches were "very" or "extremely" concerned about the risk of injury in youth sports. A majority (60.1%) believed that sport specialization was either "quite a bit" or "a great deal" of a problem. Two-thirds (67.2%) responded that year-round participation in a single sport was either "very" or "extremely" likely to increase an athlete's risk of injury. Although the responses to this survey were predominantly from coaches from 1 state, our results suggest that coaches are unaware of sport volume recommendations but are concerned about specialization. Future efforts are needed to communicate these recommendations to coaches to reduce the risk of overuse injury in youth sports.

Socioeconomic status of parents with children participating on youth club sport teams.

OBJECTIVES: To describe the socioeconomic status, measured by household income and educational attainment, of parents with children participating on youth club sport teams. DESIGN: Cross-sectional survey. SETTING: Local sport events. PARTICIPANTS: 949 parents (571 female) of youth athletes between 10 and 18 years old were recruited at club team events and practices to complete an anonymous questionnaire. MAIN OUTCOME MEASURES: SES variables included total household income (THI) and educational attainment. Sport specialization was classified as low, moderate, or high using a previously utilized 3-point specialization scale. Chi-square tests were used to compare frequencies SES categories with child specialization. RESULTS: Parents reported spending a median of 1500 [500-3000] USD per year on their children's club sports activities. Most parents reported a THI greater than 100,000 USD per year and a bachelor's degree or higher level of education. Parents in the higher THI categories were more likely to have a child that is highly specialized in one sport. CONCLUSION: The current youth sports system in the United States, which emphasizes year-round participation on club teams, may be limiting the participation of families without the resources to participate in this system.

Knowledge, Attitudes, and Beliefs of Youth Club Athletes Toward Sport Specialization and Sport Participation.

BACKGROUND: There are a variety of proposed motivations for sport specialization, such as improving sport skills to an elite level, making all-star or travel teams, or receiving a scholarship or professional contract. However, there has not been a quantitative examination of the attitudes and beliefs that may be contributing to the trend of sport specialization and year-round sport participation. PURPOSE: The primary aim was to describe the attitudes and beliefs of youth club sport athletes regarding sport specialization and sport participation. A secondary objective was to investigate whether an association exists between the level of sport specialization and the belief in receiving a college scholarship. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: A total of 974 youth athletes (578 female; mean age, 14.2 ± 1.6 years) completed an anonymous questionnaire that focused on attitudes and beliefs toward sport specialization and sport participation. Questions were developed utilizing the feedback of a panel of content area experts and the University of Wisconsin Survey Center. Data were summarized using frequencies, proportions (%), and means ± SDs. RESULTS: Fewer than half of all athletes (45.8%) believed that specialization increased their chances of getting injured either "quite a bit" or "a great deal." However, 91% of athletes believed that specialization increased their chances of getting better at their sport either "quite a bit" or "a great deal." Similarly, the majority of athletes believed that specialization increased their chances of making their high school team (80.9%) or a college team (66.9%) either "quite a bit" or "a great deal." Overall, 15.7% of athletes believed that they were either "very" or "extremely" likely to receive a college scholarship based on athletic performance. Highly specialized athletes were nearly twice as likely to have a high belief in receiving a college scholarship compared with low-specialization athletes (20.2% vs 10.2%, respectively; χ2 = 18.8; P = .001). CONCLUSION: Most youth athletes in this study believe that specialization increases their sport performance and ability to make not only a college team but also their high school team. Highly specialized athletes were more likely to believe that they will receive a college scholarship.

Greater fear of reinjury is related to stiffened jump-landing biomechanics and muscle activation in women after ACL reconstruction.

PURPOSE: Fear of reinjury is an important factor in determining who returns to sport following anterior cruciate ligament reconstruction (ACLR). Evidence from other musculoskeletal injuries indicates fear of reinjury may be related to stiffened movement patterns observed in individuals following ACLR. The relationship between fear of reinjury and performance on dynamic tasks, however, has not been investigated. Therefore, the purpose of this study was to investigate the relationship between fear of reinjury and jump-landing biomechanics. METHODS: Thirty-six females (height = 168.7 ± 6.5 cm, body mass = 67.2 ± 10.0 kg, age = 18.9 ± 1.5 years) with a history of ACLR (time from surgery = 26.1 ± 13.3 months) participated in the study. Each participant performed five trials of a standard jump-landing task. 3D motion capture and surface electromyography was used to record peak kinematics and lower extremity muscle activation on the injured limb during the jump landings. Spearman's rank correlations established the relationship between TSK-11 scores and each biomechanical variable of interest. RESULTS: There was a significant, negative relationship between fear of reinjury (TSK-11: 19.9 ± 4.5) and knee (p = 0.006), hip (p = 0.003), and trunk flexion (p = 0.013). There was also a significant, positive relationship between hip adduction (p = 0.007), and gluteus maximus preparatory activation (p = 0.001). CONCLUSIONS: The results of this study indicate that higher fear of reinjury is associated with stiffened movement patterns that are associated with increased risk of a second ACL injury. Similar movement patterns have been observed in patients with low back pain. Clinicians should evaluate psychological and emotional consequences of injury in addition to the physical consequences as they appear to be related. LEVEL OF EVIDENCE: III.

Sport Specialization Characteristics Between Rural and Suburban High School Athletes.

BACKGROUND: Sport specialization has been associated with overuse injuries and is more common in larger high schools, which are often located in more urban/suburban settings. However, sport participation characteristics have not been compared between suburban and rural high schools. PURPOSE/HYPOTHESIS: The purpose of this study was to examine the differences in sport participation characteristics between athletes at suburban and rural high schools. It was hypothesized that suburban high school students would be more likely to be highly specialized, participate in more athletic competitions per year, and play in a league outside of school. We also hypothesized that suburban high school students would start playing their primary sport at a younger age, would have participated in their primary sport for longer, and would play more months per year and hours per week. STUDY DESIGN: Cross-sectional study. METHODS: High school athletes from 4 high schools (2 suburban and 2 rural) participated in this study (N = 354 [222 females]; mean age, 15.7 ± 1.2 years). Athletes were on a school-sponsored athletic team in 1 of 4 sports (volleyball, tennis, basketball, soccer). The suburban schools (study enrollment, n = 226) had total school enrollments of 2271 and 622 students, while the rural schools (study enrollment, n = 128) had total school enrollments of 443 and 297. Participants completed a questionnaire prior to the start of their high school sport season. The questionnaire consisted of demographic information, a sport specialization scale, and sport participation information. Primary sport competition volume in the previous 12 months was classified as high (>60 primary sport competitions), moderate (30-60), or low (<30). Sport specialization status was classified via a 3-point scale as low, moderate, or high. RESULTS: As compared with athletes at rural schools, athletes at suburban schools started playing their primary sport at a younger age (suburban, 7.8 ± 2.9 years; rural, 9.7 ± 3.2 years; P < .001) and participated for more years (suburban, 7.9 ± 3.1 years; rural, 6.1 ± 3.3 years; P < .001), more months per year (suburban, 7.6 ± 3.6 months; rural, 5.6 ± 2.8 months; P < .001), and more hours per week (suburban, 15.2 ± 5.1 hours; rural, 12.9 ± 3.3 hours; P < .001). Athletes at suburban schools were more likely than rural athletes to be classified as highly specialized (χ2 = 52.5, P < .001), participate in more competitions (χ2 = 16.5, P < .001), play in a league outside of school (χ2 = 18.4, P < .001), and train in their primary sport for >8 months per year (χ2 = 27.8, P < .001) and >16 hours per week (χ2 = 15.0, P < .001). CONCLUSION: High school athletes at suburban schools are more likely to exhibit sport participation patterns that are associated with increased risk of overuse injury. These include being classified as highly specialized, playing their primary sport >8 months per year and >16 hours per week, engaging in a high competition volume, and participating in a sport league (eg, club) outside of school. Efforts aimed at safe sport participation should target these groups, as they seem more likely to violate safe sport recommendations.

Association of Competition Volume, Club Sports, and Sport Specialization With Sex and Lower Extremity Injury History in High School Athletes.

BACKGROUND: High school athletes are increasingly encouraged to participate in 1 sport year-round to increase their sport skills. However, no study has examined the association of competition volume, club sport participation, and sport specialization with sex and lower extremity injury (LEI) in a large sample of high school athletes. HYPOTHESIS: Increased competition volume, participating on a club team outside of school sports, and high levels of specialization will all be associated with a history of LEI. Girls will be more likely to engage in higher competition volume, participate on a club team, and be classified as highly specialized. STUDY DESIGN: Cross-sectional study. LEVEL OF EVIDENCE: Level 3. METHODS: High school athletes completed a questionnaire prior to the start of their competitive season regarding their sport participation and previous injury history. Multivariable logistic regression analyses were used to investigate associations of competition volume, club sport participation, and sport specialization with history of LEI, adjusting for sex. RESULTS: A cohort of 1544 high school athletes (780 girls; grades 9-12) from 29 high schools completed the questionnaire. Girls were more likely to participate at high competition volume (23.2% vs 11.0%, χ2 = 84.7, P < 0.001), participate on a club team (61.2% vs 37.2%, χ2 = 88.3, P < 0.001), and be highly specialized (16.4% vs 10.4%, χ2 = 19.7, P < 0.001). Athletes with high competition volume, who participated in a club sport, or who were highly specialized had greater odds of reporting a previous LEI than those with low competition volume (odds ratio [OR], 2.08; 95% CI, 1.55-2.80; P < 0.001), no club sport participation (OR, 1.50; 95% CI, 1.20-1.88; P < 0.001), or low specialization (OR, 2.58; 95% CI, 1.88-3.54; P < 0.001), even after adjusting for sex. CONCLUSION: Participating in high sport volume, on a club team, or being highly specialized was associated with history of LEI. Girls were more likely to participate at high volumes, be active on club teams, or be highly specialized, potentially placing them at increased risk of injury. CLINICAL RELEVANCE: Youth athletes, parents, and clinicians should be aware of the potential risks of intense, year-round participation in organized sports.

Objectively Measured Physical Activity in Patients After Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Returning to a healthy level of physical activity is among the most commonly discussed clinical goals for patients recovering from anterior cruciate ligament reconstruction (ACLR). However, physical activity has not been objectively measured in this population. PURPOSE: To investigate differences in the mean time (min/d) spent in moderate-to-vigorous physical activity (MVPA) as well as the daily step count (steps/d) between patients who underwent ACLR and matched controls. A second purpose was to investigate relationships between MVPA and objective assessments of the daily step count and Tegner and Marx activity scales. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Physical activity was assessed using ActiGraph accelerometers in 33 participants with a history of primary unilateral or bilateral ACLR (mean time from surgery, 27.8 ± 17.5 months; range, 6-67 months) as well as in 33 healthy controls (matched on age, sex, and activity level). Participants wore the accelerometer for 7 days and completed the International Knee Documentation Committee subjective form and the Tegner and Marx activity scales. Independent t tests were used to determine differences in each dependent variable per group. RESULTS: Patients who underwent ACLR spent less time in MVPA (ACLR: 79.37 ± 23.95 min/d; control: 93.12 ± 23.94 min/d; P = .02) and had a lower daily step count (ACLR: 8158 ± 2780 steps/d; control: 9769 ± 2785 steps/d; P = .02) compared with healthy matched controls. However, the Marx (ACLR median: 11.0 [interquartile range (IQR), 7-14]; control median: 12.0 [IQR, 8-13]; P = .85) and Tegner (ACLR median: 6.0 [IQR, 5-8]; control median: 7.0 [IQR, 6-8]; P = .12) scores did not differ between the groups, and no relationships were observed between objectively measured physical activity and scale measures ( P > .05), except for a moderate relationship between the Tegner score and daily step count in the ACLR group ( r = 0.36, P = .04). Only 24% of patients who underwent ACLR met the guideline of 10,000 steps per day compared with 42% of controls. CONCLUSION: Patients who underwent ACLR spent less time in MVPA and had a lower daily step count compared with highly matched controls (age, sex, and activity level) with no history of knee injuries. This was true despite being similar in activity levels, which brings into question the utility of the Tegner and Marx activity scales.

The Effects of Specialization and Sex on Anterior Y-Balance Performance in High School Athletes.

BACKGROUND: Sport specialization and movement asymmetry have been separately discussed as potential risk factors for lower extremity injury. Early specialization may lead to the development of movement asymmetries that can predispose an athlete to injury, but this has not been thoroughly examined. HYPOTHESIS: Athletes rated as specialized would exhibit greater between-limb anterior reach asymmetry and decreased anterior reach distance on the Y-balance test (YBT) as compared with nonspecialized high school athletes, and these differences would not be dependent on sex. STUDY DESIGN: Cross-sectional study. LEVEL OF EVIDENCE: Level 3. METHODS: Two hundred ninety-five athletes (117 male, 178 female; mean age, 15.6 ± 1.2 years) from 2 local high schools participating in basketball, soccer, volleyball, and tennis responded to a questionnaire regarding sport specialization status and performed trials of the YBT during preseason testing. Specialization was categorized according to 3 previously utilized specialization classification methods (single/multisport, 3-point scale, and 6-point scale), and interactions between specialization and sex with Y-balance performance were calculated using 2-way analyses of variance. RESULTS: Single-sport male athletes displayed greater anterior reach asymmetry than other interaction groups. A consistent main effect was observed for sex, with men displaying greater anterior asymmetry and decreased anterior reach distance than women. However, the interaction effects of specialization and sex on anterior Y-balance performance varied based on the classification method used. CONCLUSION: Single-sport male athletes displayed greater anterior reach asymmetry on the YBT than multisport and female athletes. Specialization classification method is important because the 6- and 3-point scales may not accurately identify balance abnormalities. Male athletes performed worse than female athletes on both of the Y-balance tasks. CLINICAL RELEVANCE: Clinicians should be aware that single-sport male athletes may display deficits in dynamic balance, potentially increasing their risk of injury.

The Association of Sport Specialization and Training Volume With Injury History in Youth Athletes.

BACKGROUND: Recommendations exist to encourage safe youth participation in sport. These recommendations include not specializing in 1 sport, limiting participation to less than 8 months per year, and limiting participation to fewer hours per week than a child's age. However, limited evidence exists to support or refute these recommendations. HYPOTHESIS: High levels of specialization will be associated with a history of injuries and especially overuse injuries, independent of age, sex, or weekly sport training hours. Athletes who exceed current sport volume recommendations will be more likely to have a history of injuries and overuse injuries. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: Youth athletes (n = 2011; 989 female and 1022 male; 12-18 years of age) completed a questionnaire regarding their specialization status, yearly and weekly sport participation volume, and injury history. Specialization was classified as low, moderate, or high using a previously utilized 3-point scale. Athletes were classified into groups based on either meeting or exceeding current volume recommendations (months per year and hours per week). Odds ratios (ORs) and 95% CIs were calculated to investigate associations of specialization and volume of participation with a history of sport-related injuries in the past year ( P ≤ .05). RESULTS: Highly specialized athletes were more likely to report a previous injury of any kind ( P < .001; OR, 1.59; 95% CI, 1.26-2.02) or an overuse injury ( P = .011; OR, 1.45; 95% CI, 1.07-1.99) in the previous year compared with athletes in the low specialization group. Athletes who played their primary sport more than 8 months of the year were more likely to report an upper extremity overuse injury ( P = .04; OR, 1.68; 95% CI, 1.06-2.80) or a lower extremity overuse injury ( P = .001; OR, 1.66; 95% CI, 1.22-2.30). Athletes who participated in their primary sport for more hours per week than their age (ie, a 16-year-old athlete who participated in his or her primary sport for more than 16 h/wk) were more likely to report an injury of any type ( P = .001; OR, 1.34; 95% CI, 1.12-1.61) in the previous year. CONCLUSION: High levels of specialization were associated with a history of injuries, independent of age, sex, and weekly organized sport volume. Athletes who exceeded volume recommendations were more likely to have a history of overuse injuries. CLINICAL RELEVANCE: Parents and youth athletes should be aware of the risks of specialization and excessive sport volume to maximize safe sport participation.

Landing mechanics during single hop for distance in females following anterior cruciate ligament reconstruction compared to healthy controls.

PURPOSE: To determine possible differences in single-hop kinematics and kinetics in females with anterior cruciate ligament reconstruction compared to healthy controls. A second purpose was to make comparisons between the healthy and reconstructed limbs. METHODS: Subjects were grouped based on surgical status (33 ACLR patients and 31 healthy controls). 3D motion capture synchronized with force plates was used to capture the landing phase of three successful trials of single hop for distance during a single data collection session. Peak values during the loading phase were analysed. Subjects additionally completed three successful trials of the triple hop for distance Tegner activity scale and International Knee Document Committee 2000 (IKDC). RESULTS: Controls demonstrated greater peak knee flexion and greater internal knee extension moment and hip extension moment than ACLR subjects. Within the ACLR group, the healthy limb exhibited greater peak knee flexion, hip flexion, hip extension moment, single hop and triple hops for distance and normalized quadriceps strength. CONCLUSION: Patients who undergo anterior cruciate ligament reconstruction land in a more extended posture when compared to healthy controls and compared to their healthy limb. LEVEL OF EVIDENCE: III.

High School Sport Specialization Patterns of Current Division I Athletes.

BACKGROUND: Sport specialization is a strategy to acquire superior sport performance in 1 sport but is associated with increased injury risk. Currently, the degree of high school specialization among Division I athletes is unknown. HYPOTHESIS: College athletes will display increased rates of specialization as they progress through their high school careers. STUDY DESIGN: Descriptive epidemiological study. LEVEL OF EVIDENCE: Level 4. METHODS: Three hundred forty-three athletes (115 female) representing 9 sports from a Midwest Division I University completed a previously utilized sport specialization questionnaire regarding sport participation patterns for each grade of high school. McNemar and chi-square tests were used to investigate associations of grade, sport, and sex with prevalence of sport specialization category (low, moderate, high) (a priori P ≤ 0.05). RESULTS: Specialization increased throughout high school, with 16.9% (n = 58) and 41.1% (n = 141) of athletes highly specialized in 9th and 12th grades, respectively. Football athletes were less likely to be highly specialized than nonfootball athletes for each year of high school ( P < 0.001). There was no difference in degree of specialization between sexes at any grade level ( P > 0.23). CONCLUSION: The majority of Division I athletes were not classified as highly specialized throughout high school, but the prevalence of high specialization increased as athletes progressed through high school. Nonfootball athletes were more likely to be highly specialized than football athletes at each grade level. CLINICAL RELEVANCE: Most athletes who are recruited to participate in collegiate athletics will eventually specialize in their sport, but it does not appear that early specialization is necessary to become a Division I athlete. Athletes should be counseled regarding safe participation in sport during high school to minimize injury and maximize performance.

Hip Strength in Patients with Quadriceps Strength Deficits after ACL Reconstruction.

PURPOSE: Quadriceps strength deficits persist for years after anterior cruciate ligament (ACL) reconstruction, and patients with these deficits often shift torque demands away from the knee extensors to the hip during functional tasks. However, it is not clear how quadriceps strength deficits may affect hip strength. Therefore, the purpose of this study was to investigate differences in lower extremity strength in individuals with ACL reconstruction with differing levels of quadriceps strength asymmetry. METHODS: Isometric strength was recorded bilaterally in 135 participants (73 control and 62 with unilateral ACL reconstruction, time from surgery = 30.9 ± 17.6 months) from the knee extensors and flexors, hip extensors and abductors, and hip internal and external rotator muscle groups. Symmetry indices (limb symmetry index (LSI)) were created based on quadriceps strength, and subjects with ACL reconstruction were subdivided (high quadriceps (LSI ≥ 90%), n = 37; low quadriceps (LSI < 85%), n = 18). Individual group (control vs high quadriceps vs low quadriceps) by limb (reconstructed/nondominant vs healthy/dominant) repeated-measures ANOVA was used to compare strength (%BW) for each of the six joint motions of interest (knee extensors/flexors, hip abductors/extensors/external, and internal rotators) while controlling for time from surgery. RESULTS: An interaction was observed for quadriceps strength (P < 0.001), and the reconstructed limb in the low quadriceps group was weaker than all other limbs. A main effect for group was observed with the low quadriceps group having greater hip extension (P = 0.007) strength in both limbs compared with the other groups. Knee flexion strength was weaker in the reconstructed limb of the high quadriceps group (P = 0.047) compared with all other groups and limbs. CONCLUSIONS: Individuals with ACL reconstruction and involved limb quadriceps weakness have greater hip extension strength in both limbs compared with patients with bilateral strength symmetry and controls.

Prevalence of Sport Specialization in High School Athletics: A 1-Year Observational Study.

BACKGROUND: The prevalence of sport specialization in high school athletes is unknown. This information is needed to determine the scope of this issue in an active population. PURPOSE: To determine the prevalence of sport specialization in high school athletes and to determine if specialization is influenced by classification method, year in school, sex, and school size. A secondary purpose was to determine if highly specialized athletes would be more likely to report a history of lower extremity injuries. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: High school athletes between the ages of 13 and 18 years from 2 local high schools completed both a sport specialization survey and an injury history survey. Athletes were classified into low, moderate, or high specialization groups using a recently developed 3-point system and were also classified using a self-classification method. RESULTS: A total of 302 athletes completed the surveys and were classified as low specialization (n = 105, 34.8%), moderate specialization (n = 87, 28.8%), or high specialization (n = 110, 36.4%). Athletes from the small school were more likely to be classified in the low specialization group (low, 43%; moderate, 32%; high, 25%) compared with those from the large school (low, 26%; moderate, 26%; high, 48%) (P < .001). Athletes in the high specialization group were more likely to report a history of overuse knee injuries (n = 18) compared with moderate (n = 8) or low specialization (n = 7) athletes (P = .048). Athletes who trained in one sport for more than 8 months out of the year were more likely to report a history of knee injuries (odds ratio [OR], 2.32; 95% CI, 1.22-4.44; P = .009), overuse knee injuries (OR, 2.93; 95% CI, 1.16-7.36; P = .018), and hip injuries (OR, 2.74; 95% CI, 1.09-6.86; P = .026). Using the self-classification method, more participants self-classified as multisport (n = 213, 70.5%) than single sport (n = 89, 29.5%). Athletes from the small school were more likely to classify themselves as multisport (n = 128, 86%) (P < .001) than those from the large school (n = 85, 56%). There were no differences in the history of hip, knee, or ankle injuries between athletes who self-classified as single sport (hip: n = 10, 3%; knee: n = 19, 6%; ankle: n = 35, 12%) versus those who self-classified as multisport (hip: n = 45, 8%; knee: n = 23, 15%; ankle: n = 98, 33%) (P > .370). CONCLUSION: Classification method and school size influenced the prevalence of specialization in high school athletes. Highly specialized athletes were more likely to report a history of overuse knee or hip injuries. Participating in a single sport for more than 8 months per year appeared to be an important factor in the increased injury risk observed in highly specialized athletes.

The Effect of Exertion and Sex on Vertical Ground Reaction Force Variables and Landing Mechanics.

The purpose of this investigation was to determine how exertion and sex affected a variety of vertical ground reaction force (VGRF) parameters during a jump-landing task, including peak VGRF, peak VGRF asymmetry, loading rate, and loading rate asymmetry. Additionally, we wanted to determine whether landing mechanics changed after exertion as measured by the Landing Error Scoring System (LESS). Forty recreationally active participants (20 men and 20 women) completed jump landings from a 30-cm-high box onto force plates before and after repeated bouts of an exercise circuit until a specific rating of perceived exertion was achieved. Three-way (sex × time × limb) analyses of variance were used to analyze variables pre-exertion to postexertion. No significant 3-way interactions were observed for peak VGRF (p = 0.31) or loading rate (p = 0.14). Time by sex interactions were observed for peak VGRF (p = 0.02) and loading rate (p = 0.008). Post hoc analysis revealed that men increased landing force and loading rate after exertion while women did not. Landing mechanics, as assessed by total LESS score, were worse after exertion (p < 0.001) with increased frequency of errors for knee flexion <30° at initial contact, lateral trunk flexion, and not flexing the hip during landing. Women may be more resistant to exertion compared with men and use different joint controls' strategies to cope with VGRF after exertion. However, VGRF asymmetry is not affected by sex and exertion. Limiting peak VGRF and addressing landing postures, especially after exertion, should be components of injury prevention strategies.