Youth American Football Research Articles

Do American Youth Football Players Intentionally Use Their Heads for High-Magnitude Impacts?

Background: Concern for head injuries is widespread and has been reported by the media to be the number one cause of decreased participation in football among the American youth population. Identifying player mechanisms associated with intentional, or purposeful, head impacts should provide critical data for rule modifications, educational programs, and equipment design. Purpose: To investigate the frequency of intentional and unintentional head impacts and to examine the player mechanisms associated with intentional high-magnitude head impacts by comparing the impact mechanism distributions among session type, player position, and ball possession. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Head impact sensors and video footage of 68 players were used to analyze and classify 1319 high-magnitude impacts recorded over 1 season of youth football. Results: In total, 80% of the high-magnitude head impacts were classified as being caused by intentional use of the head. Head-to-head impact was the primary impact mechanism (n = 868; 82.7%) within the 1050 intentional high-magnitude impacts, with classifiable mechanisms, followed by head-to-body (n = 139; 13.2%), head-to-ground (n = 34; 3.2%), and head-to-equipment (n = 9; 0.9%). Head-to-head impacts also accounted for a greater proportion of impacts during practices (n = 625; 88.9%) than games, for linemen (n = 585; 90.3%) than perimeters and backs, and for ball carriers (n = 72; 79.1%) than tacklers. Conclusion: Overall, the majority of high-magnitude head impacts were intentional and resulted from head-to-head contact. The proportion of head-to-head contact was significantly higher for practices than games, linemen than backs and perimeter players, and ball carriers than tacklers.

Descriptive Analysis of Youth American Football Quarterback Injuries: A 15-years of Retrospective Data Study

PURPOSE: To describe the common injuries of youth American football (FB) quarterbacks (QBs) within the last 15 years. METHODS: A retrospective chart review of all patients cared for in a sports medicine clinic of an academic pediatric medical center between 01/01/2003 - 10/01/2018. Patients were identified using the search engine HoundDog to search the term “quarterback.” Records were then reviewed to identify all QBs < 18 years of age. Injures that were not associated with FB participation were excluded. Main outcome variables were injured anatomic locations, injury types, surgical status, and settings in which the injury was sustained. Descriptive statistics were used to analyze the outcome variables. RESULTS: A total of 374 male QBs (mean age: 14.6±2.1) sustained a total of 423 injuries. The top 5 injured anatomic locations (Figure 1) were shoulder (22.2%), knee (15.5%) head/neck (14.5%), elbow (13.6%), and wrist/hand/lower arm (11.3%). The injuries consisted of 64.3% in acute mechanism and 35.7% chronic in nature. The acute injuries occurred during game competition (55.5%), practice (14.3%), and off-season (6.7%); for the remaining 23.5% there was not sufficient documentation in the medical record to determine the setting. Of the chronic injuries, 47.0% occurred during off-season and 34.4% occurred in-season; for 15.2% of the chronic injuries there was not sufficient documentation in the medical record to determine the setting. Among all injuries, 22.9% were surgical cases, and the top 3 anatomic locations of surgery were knee (35.0%), shoulder (20.7%), and elbow (18.7%). CONCLUSIONS: The shoulder is the most commonly injured body part among young QBs seeking care in a specialty sports medicine clinic, although the knee is the most commonly injured body part that requires surgery. Quarterback injuries are primarily acute in mechanism, and the majority of these acute injuries occur during game competition.

Exertional heat illness risk factors and physiological responses of youth football players

ObjectiveTo determine which intrinsic and extrinsic exertional heat illness (EHI) risk factors exist in youth American football players and observe perceptual and physiological responses of players during events (games and practices). MethodsCross-sectional cohort study observing 63 youth football players, varying in position. Independent variables were league (weight-restricted (WR, n = 27) and age-restricted (AR, n = 36)) and event type. Dependent variables were anthropometrics, work-to-rest ratio, and wet bulb globe temperature. Descriptive variables included preparticipation examination and uniform configuration. A subset of 16 players participated in physiological variables (heart rate and gastrointestinal temperature). Data collection occurred on 7 AR and 8 WR nonconsecutive practices and the first 3 games of the season. ResultsMean values for anthropometric variables were higher (p < 0.05) in the AR league than the WR league. Work time (χ2 (1,111) = 4.232; p = 0.039) and rest time (χ2 (1,111) = 43.41; p < 0.001) were significantly greater for games, but ratios were significantly higher for practices (χ2 (1,111) = 40.62; p < 0.001). The majority of events (77%) observed were in black and red flag wet bulb globe temperature risk categories. A total of 57% of the players had a preparticipation examination, and up to 82% of events observed were in full uniforms. Individual gastrointestinal temperature and heart rate responses ranged widely and no players reached critical thresholds. ConclusionExtrinsic (disproportionate work ratios, environmental conditions) and intrinsic (higher body mass index) EHI risk factors exist in youth football. Certain risk factors may be influenced by event and league type. National youth football organizations need to create thorough guidelines that address EHI risk factors for local leagues to adopt.

Sleep correlates of brain network activation and clinical measures in youth American football players

Sleep correlates of brain network activation and clinical measures in youth American football players

Current trends in sport injury prevention

Participation in sport and recreation has important positive implications for public health across the lifespan; however, the burden of sport-related musculoskeletal injury is significant, with the greatest risk being in youth and young adults. Moving upstream to primary prevention of injury is a public health priority that will have significant implications for reducing the long-term consequences of musculoskeletal injury including early post-traumatic osteoarthritis. The primary targets for the prevention of musculoskeletal injury in sport include neuromuscular training (NMT), rule modification, and equipment recommendations. Currently, there is significant high-quality evidence to support the widespread use of NMT warm up programs in team and youth sport, with an expected significant impact of reducing the risk of musculoskeletal injury by over 35%. Policy disallowing body checking in youth ice hockey has led to a >50% reduction in injuries, and rules limiting contact practice in youth American football has significant potential for injury prevention. There is evidence to support the use of bracing and taping in elite sport to reduce the risk of recurrent ankle sprain injury but not for use to prevent the primary injury, and wrist guards are protective of sprain injuries in snowboarding. Future research examining the maintenance of NMT programs across real-world sport and school settings, optimization of adherence, additional benefit of workload modification, and evaluation of rule changes in other sports is needed.

Association between relative age effect and organisational practices of American youth football

ABSTRACTThe popular method of organising youth sport participants into age divisions, based solely on their birthdate, can result in an imbalance of the distribution of players. This is known as relative age effect (RAE), which inadvertently creates bias and is associated with deleterious short and long-term consequences. The overall purpose of this study was to examine how the potential for RAE is mitigated when simultaneously accounting for additional player criterion, supplementary to age. A mid-Atlantic American youth football registration database was acquired, including chronological (age), anthropometric (weight), and competency (skill) factors. Player (n = 1,265) data were classified into quartiles and multiple chi-square goodness of fit tests were conducted using proportions of live births as expected theoretical distribution values. When data were categorised by a single developmental criterion (e.g. age), results indicated significant departures (p ≤ 0.002) from expected proportions. However, when categorised using multiple criteria (i.e. age, weight, and skill), equitable birthdate distributions were observed. Findings from this study indicate using only one developmental criterion for organising players is associated with RAE, whereas approaches accounting for multiple variables are not associated with RAE. This study provides youth football programs with early evidence for considering alternative methods of organising players.

Head impact exposure and time to recovery in youth american football players diagnosed with a concussion

ObjectiveTo compare head impact exposure (HIE) sustained by youth American football players on days of concussion with prior sessions, and to evaluate concussion resolution with objective assessments.DesignProspective,observational study.SettingYouth American football.ParticipantsYouth American football players (11-14 yr, n=57) who had head impact sensors embedded in their helmets; six were diagnosed with a concussion.InterventionsOver four consecutive seasons, baseline and post-injury concussion assessments were performed and HIE was monitored (Head Impact Telemetry system) for all practice/game sessions.Outcome measuresBaseline/Post-concussion assessments – symptoms, balance, reaction time, neurocognitive function (ImPACT), and oculomotor performance (King-Devick). HIE – location, frequency, and magnitude (linear acceleration [LA] and rotational acceleration [RA]).Main resultsFor concussive impacts, the average peak LA was 85.9g(39.7-156.8g) and average peak RA was 6918rad·sec-2(4508-8433rad·sec-2). On average, players sustained 21.3 impacts/session on days of concussion vs. 10.2 in previous sessions. Median LA and RA did not differ on days of concussion when compared to prior sessions (21.9 vs. 20.7g; 1480 vs. 1485 rad·sec-2). Average duration for a concussed player to have his assessment values return to baseline and be cleared for play was 32 days (17-53).ConclusionsConsiderable variation in magnitude existed between impacts that lead to concussion in this population. Players sustained more head impacts in sessions with a concussion compared to prior sessions. Frequency and magnitude of head impacts on the day of concussion did not correlate with time to recovery. Continued observation of a larger cohort is warranted.Competing interestsNone.

Environmental Conditions and Seasonal Variables in American Youth Football Leagues.

Our study describes youth football (YFB) environmental conditions and the associated heat index (HI) risk category. An observational research design was utilized. Independent variables included month, time, event, and geographic location. Main outcome variables were frequency of events, average HI, and corresponding risk categorization. The HI was recorded with the day and time for each YFB event across 2 YFB seasons. Nearly half (49.8%) of events were in a high HI risk category and 20.0% should have been cancelled. The hottest HI values were recorded in July and August (83.2 ± 9.4°F to 87.2 ± 10.9°F; 24.0% of YFB events). The 7 to 10 am time frame was cooler (67.7 ± 14.5°F; 6.3% of YFB events) than other time frames ( P < .001). Hotter HI values were recorded in practices versus games (75.9 ± 14.1°F vs 70.6 ± 14.6°F; t = -6.426, P < .001). Starting the YFB season in September and holding weekend events in the early morning hours can decrease exposure to environmental heat stress.

Sport Parent Perceptions of American Youth Football Costs, Benefits, and Safety

As head injuries in American football have received increasing publicity, the safety of the sport has become a great concern for parents nationwide. The purpose of this study was to examine perceived safety concerns in youth football using Eccles’ expectancy-value model (Eccles et al., 1983). We hypothesized perceived safety concerns to moderate relationships between parent perceptions of parent cost/benefit, child cost/benefit, and child motivation and enjoyment outcomes for football. Youth football parents (N = 105, Mage = 42) completed valid and reliable online assessments of study variables. Regression analyses revealed child safety concerns (as rated by parents) to mediate, rather than moderate, the relationship between parent safety concerns and child cost perceptions (as rated by parents). Furthermore, safety concerns did not significantly associate with child achievement outcomes of motivation and enjoyment. Results provide valuable insight into parent and child attitudes toward youth football safety. Such knowledge may inform future educational interventions targeting sport safety promotion.

Anthropometrics, Physical Performance, and Injury Characteristics of Youth American Football.

Background:Prior research has described the anthropometric and physical performance characteristics of professional, collegiate, and high school American football players. Yet, little research has described these factors in American youth football and their potential relationship with injury.Purpose:To characterize anthropometric and physical performance measures, describe the epidemiology of injury, and examine the association of physical performance measures with injury among children participating within age-based divisions of a large metropolitan American youth football league.Study Design:Case-control study; Level of evidence, 3.Methods:Demographic, anthropometric, and physical performance characteristics and injuries of 819 male children were collected over a 2-year period (2011-2012). Injury data were collected by the league athletic trainer (AT) and coaches. Descriptive analysis of demographic, anthropometric, and physical performance measures (40-yard sprint, pro-agility, push-ups, and vertical jump) were conducted. Incidence rates were computed for all reported injuries; rates were calculated as the number of injuries per 1000 athlete-exposures (AEs). Multinomial logistic regression was used to identify whether the categories of no injury, no-time-loss (NTL) injury, and time-loss (TL) injury were associated with physical performance measures.Results:Of the 819 original participants, 760 (92.8%) completed preseason anthropometric measures (mean ± SD: age, 11.8 ± 1.2 years; height, 157.4 ± 10.7 cm; weight, 48.7 ± 13.3 kg; experience, 2.0 ± 1.8 years); 640 (78.1%) players completed physical performance measures. The mean (±SD) 40-yard sprint and pro-agility measures of the players were 6.5 ± 0.6 and 5.7 ± 0.5 seconds, respectively; the number of push-ups and maximal vertical jump height were 16.5 ± 9.3 repetitions and 42.3 ± 8.4 cm, respectively. Players assigned to different teams within age divisions demonstrated no differences in anthropometric measures; 40-yard dash and pro-agility times differed significantly (P < .05) between players assigned to different teams. A total of 261 NTL and TL injuries were reported during 35,957 AEs (games: 22%, n = 7982 AEs; practices: 78%, n = 27,975 AEs). The overall incidence rate was 7.26 per 1000 AEs (95% CI, 6.37-8.14). Physical performance measures did not predict NTL or TL injuries (P > .05).Conclusion:No practically meaningful differences existed in anthropometric or physical performance measures between teams within age-based levels of play. Findings suggest that age-only criterion for player groupings can evenly match in terms of physical performance.

Inter-rater Agreement of a Tackling Performance Assessment Scale in Youth American Football.

Recommendations have been made regarding appropriate tackling form to reduce the risk of head injury, including the USAFootball HeadsUp tackling program. Providing feedback on technique is an essential part of improving performance and decreasing injury risk. PURPOSE:Establish inter-rater agreement of a Tackling Performance Assessment s scale to be used for delivering feedback to youth football players. METHODS:Twenty videos of youth football athletes performing a football tackle on a dummy were presented to two Certified Athletic Trainers (ATC). These ATCs were provided with training regarding the desired tackle performance, as recommended by USA Football, and completed a self-test with a minimum score of 80%. After completion of rater training, participants were asked to identify correct performance of six criteria on a dichotomous scale. The videos could be slowed to half speed or advanced frame by frame, if desired. Criteria include the following measures upon contact: cervical extension >45°, trunk inclination between 35° and 55°, head placement on far side of target, and pelvic height less than 75% of standing pelvis height. Criteria upon approach include: shoulder extension >45° and step length <70% of standing pelvis height. Cohen’s Kappa statistics were calculated to assess inter-rater agreement for each of the six components of the scale. RESULTS:Cohen’s Kappa measures found substantial agreement in cervical extension (κ=0.694), head placement (κ=0.608), pelvic height (κ=0.737), and shoulder extension (κ=0.700). Step length has moderate agreement (κ=0.494) and trunk inclination has fair agreement (κ=0.241). CONCLUSIONS:Inter-rater agreement of the six critical components range from fair to substantial. While visual estimation is not considered the most accurate or reliable mechanism to measure movement, this strategy is utilized regularly by clinicians and coaches and requires little to no additional equipment. Results of this study indicate trained personnel were able to achieve moderate to substantial agreement in four of 6 assessment areas, indicating the raters are capable of identifying the appropriate feedback to be provided. By establishing a feedback mechanism that is easily utilized by clinicians and coaches we can begin to provide a pathway to improve tackling performance.

Epidemiology Of Knee Sprains In Youth, High School, And Collegiate American Football

Epidemiology Of Knee Sprains In Youth, High School, And Collegiate American Football

Head and Neck Circumference Not Risk Factors For Game Concussions Among Youth American Football Players

Neck to head circumference ratio (NHR) has been reported as a potential risk factor for concussion (CONC) among high school athletes. Research examining anthropometrics and neck (NC) and head (HC) circumferences and NHR in youth football is limited. PURPOSE: To examine the relationship between player anthropometrics and CONC injury rates (IR) among youth football players. METHODS: 1212 male youth football players (11.9±1.2 years) with 2.6±1.9 years experience participating in a large metropolitan youth football league were followed prospectively throughout 3 seasons (2012-2014). Height (HT, cm); weight (WT, kg); and NC and HC, cm; data were collected pre-season. CONC injury information, including mechanism of injury (MOI, for games was tracked each season by the leagues certified athletic trainer (AT) using an electronic medical record-keeping system. At each event, ATs collected injury and athlete-exposure (AE) data. CONC injury frequencies and rates with 95% confidence intervals (CI) were calculated based on 1000 AE. Descriptive statistics characterized anthropometrics and CONC. Binary logistic regression with forward step-wise elimination examined relationships between anthropometric characteristics (HT, WT, BMI, HC, NC, NHR) and the incidence of CONC (p≤0.05). RESULTS: Participants (n=1068) mean anthropometrics’: 157.4cm, 49.8kg, and 21.8.kg/m2. The mean NC, HC and HNR ratio (n=951): 32.2cm, 52.07cm, and 0.53, respectively. 71 of 1212 participants (5.9%) were diagnosed with a CONC. CONC IR for games for all 3 seasons was 5.65 /1000 AE (95%CI: 4.34 -6.97). Majority CONC occurred during the 2nd half of play (n=52, 73.3%) as a result of helmet-to-helmet (31, 43.7%), and head-to-ground (n=15, 21.1%) collisions. Binary logistic regression identified no significant predictors of concussion 2(1, N=854)=94%, p = .92. CONCLUSIONS: Incidence of CONC was similar to those previously reported in same age group of youth football players. While anthropometrics, NC, HC and NHR and BMI did not predict CONC, future research should examine these factors as well as neck strength as potential predictors of CONC. Research should also examine if the high incidence of CONC during the 2nd half of game play is related with other modifiable risk factors. Supported by Potomac Health Foundation.

Comprehensive Coach Education Reduces Head Impact Exposure in American Youth Football.

Background:Despite little evidence that defines a threshold of head impact exposure or that participation in youth sports leads to long-term cognitive impairments, it is prudent to identify methods of reducing the frequency of head impacts.Purpose:To compare the mean number of head impacts between youth football players in practice and games between leagues that implemented the Heads Up Football (HUF) educational program and those that did not (NHUF).Study Design:Cohort study; Level of evidence, 2.Methods:During the 2014 season, head impact exposure was measured using xPatch accelerometers from 70 youth football players aged 8 to 15 years from 5 leagues. Data were collected during both games and practices. The NHUF group comprised 32 players from 8 teams within 3 leagues. The HUF group comprised 38 players from 7 teams within 2 leagues. Independent-sample t tests evaluated differences in head impact exposure across groups (ie, HUF and NHUF).Results:Players (mean ± SD: age, 11.7 ± 1.4 years; height, 152.2 ± 10.5 cm; weight, 51.6 ± 9.6 kg) experienced a total of 7478 impacts over 10g, of which 4250 (56.8%) and 3228 (43.2%) occurred in practices and games, respectively. The majority of impacts occurred within the NHUF group (62.0%), followed by the HUF group (38.0%). With a 10g impact threshold, the mean number of impacts during practice per individual event was lower in the HUF group (mean ± SD, 5.6 ± 2.9) than in the NHUF group (mean ± SD, 8.9 ± 3.1; difference, 3.4; 95% CI, 2.9-3.9). This difference was attenuated when the threshold was changed to 20g but remained significant (difference, 1.0; 95% CI, 0.7-1.3). At both the 10g and 20g impact thresholds, no differences were found in games.Conclusion:Players who participated in HUF leagues accumulated fewer head impacts per practice at both the 10g and 20g thresholds. Youth football leagues should consider the HUF educational program, while exploring additional interventions, to help reduce the number of head impacts in players.

Injury Rates in Age-Only Versus Age-and-Weight Playing Standard Conditions in American Youth Football.

Background:American youth football leagues are typically structured using either age-only (AO) or age-and-weight (AW) playing standard conditions. These playing standard conditions group players by age in the former condition and by a combination of age and weight in the latter condition. However, no study has systematically compared injury risk between these 2 playing standards.Purpose:To compare injury rates between youth tackle football players in the AO and AW playing standard conditions.Study Design:Cohort study; Level of evidence, 2.Methods:Athletic trainers evaluated and recorded injuries at each practice and game during the 2012 and 2013 football seasons. Players (age, 5-14 years) were drawn from 13 recreational leagues across 6 states. The sample included 4092 athlete-seasons (AW, 2065; AO, 2027) from 210 teams (AW, 106; O, 104). Injury rate ratios (RRs) with 95% CIs were used to compare the playing standard conditions. Multivariate Poisson regression was used to estimate RRs adjusted for residual effects of age and clustering by team and league. There were 4 endpoints of interest: (1) any injury, (2) non–time loss (NTL) injuries only, (3) time loss (TL) injuries only, and (4) concussions only.Results:Over 2 seasons, the cohort accumulated 1475 injuries and 142,536 athlete-exposures (AEs). The most common injuries were contusions (34.4%), ligament sprains (16.3%), concussions (9.6%), and muscle strains (7.8%). The overall injury rate for both playing standard conditions combined was 10.3 per 1000 AEs (95% CI, 9.8-10.9). The TL injury, NTL injury, and concussion rates in both playing standard conditions combined were 3.1, 7.2, and 1.0 per 1000 AEs, respectively. In multivariate Poisson regression models controlling for age, team, and league, no differences were found between playing standard conditions in the overall injury rate (RRoverall, 1.1; 95% CI, 0.4-2.6). Rates for the other 3 endpoints were also similar (RRNTL, 1.1 [95% CI, 0.4-3.0]; RRTL, 0.9 [95% CI, 0.4-1.9]; RRconcussion, 0.6 [95% CI, 0.3-1.4]).Conclusion:For the injury endpoints examined in this study, the injury rates were similar in the AO and AW playing standards. Future research should examine other policies, rules, and behavioral factors that may affect injury risk within youth football.

Comprehensive Coach Education and Practice Contact Restriction Guidelines Result in Lower Injury Rates in Youth American Football.

Background:Research evaluating the effect of comprehensive coach education and practice contact restriction in youth football injury rates is sparse. In 2012, USA Football released their Heads Up Football coaching education program (HUF), and Pop Warner Football (PW) instituted guidelines to restrict contact during practice.Purpose:To compare injury rates among youth football players aged 5 to 15 years by whether their leagues implemented HUF and/or were PW-affiliated.Study Design:Cohort study; Level of evidence, 2.Methods:Athletic trainers (ATs) evaluated and tracked injuries at each practice and game during the 2014 youth football season. Players were drawn from 10 leagues across 4 states. The non–Heads Up Football (NHUF) group consisted of 704 players (none of whom were PW-affiliated) from 29 teams within 4 leagues. The HUF+PW group consisted of 741 players from 27 teams within 2 leagues. The HUF-only group consisted of 663 players from 44 teams within 4 leagues. Injury rates and injury rate ratios (IRRs) were reported with 95% CIs.Results:A total of 370 injuries were reported during 71,262 athlete-exposures (AEs) (rate, 5.19/1000 AEs). Compared with the NHUF group (7.32/1000 AEs), the practice injury rates were lower for the HUF+PW group (0.97/1000 AEs; IRR, 0.13; 95% CI, 0.08-0.21) and the HUF-only group (2.73/1000 AEs; IRR, 0.37; 95% CI, 0.26-0.53). Compared with the NHUF group (13.42/1000 AEs), the game injury rate was lower for the HUF+PW group (3.42/1000 AEs; IRR, 0.25; 95% CI, 0.15-0.44) but not for the HUF-only group (13.76/1000 AEs; IRR, 1.02; 95% CI, 0.73-1.43). Also, the HUF+PW game injury rate was lower than that of HUF-only (IRR, 0.20; 95% CI, 0.12-0.36). Higher injury rates were typically found in those aged 11 to 15 years compared with those aged 5 to 10 years. However, stronger effects related to HUF implementation and PW affiliation were seen among 11- to 15-year-olds. When restricted to concussions only, the sole difference was found between the practice concussion rates among 11- to 15-year-olds in the HUF+PW (0.14/1000 AEs) and NHUF groups (0.79/1000 AEs) (IRR, 0.18; 95% CI, 0.04-0.85).Conclusion:These findings support comprehensive coach education and practice contact restrictions as effective methods of injury mitigation. Future research should continue evaluating similar programming within other levels of competition and sports.

Effects of an Injury Prevention Program on Injury Rates in American Youth Football

The purpose of this study was to determine if the time-loss (TLIR) and non-time-loss injury rates (NTLIR) in youth football were decreased by the implementation of the P.R.E.P.A.R.E injury prevention program. This study consisted of two groups: coaches and players. Some coaches took the program and select elements of the program were instituted. The injury rates (IR) in the players were compared pre and post. There was a reduction of some of the IRs during the intervention season. This reduction may be due in part to some of the coaches completing the entire program and all of the coaches instituting six elements of the program. Continued research is needed to determine if the IRs, in youth football, are consistently reduced by implementation of the program. Further research is needed to examine the impact of coaches taking and implementing the program on the reduction of injuries in other youth sports.

Validation of a Noninvasive Maturity Estimate Relative to Skeletal Age in Youth Football Players

To validate a non-invasive measure of biological maturity (percentage of predicted mature height at a given age) with an established indicator of maturity [skeletal age (SA)] in youth American football players. Cross-sectional. Two communities in central Michigan. 143 youth football players 9.27 to 14.24 years. Height and weight were measured, and hand-wrist radiographs were taken. SA assessed with the Fels method was the criterion measure of maturity status. Chronological age (CA), height, and weight of the player and midparent height were used to predict mature height; current height of the player was expressed as a percentage of his predicted mature height as a noninvasive estimate of biological maturity status. Boys' maturation was classified as late, on time, or early maturing on the basis of the difference between SA and CA and of present height expressed as a percentage of predicted mature height. Kappa coefficients and Spearman rank-order correlations were calculated. Characteristics of players concordant and discordant for maturity classification with SA and percentage of predicted mature height were compared with MANCOVA. Concordance between methods of maturity classification was 62%. The Kappa coefficient, 0.46 (95% CI 0.19 to 0.59) and Spearman rank-order correlation, rs = 0.52 (P < 0.001) were moderate. Players discordant for maturity status varied in midparent height and percentage of predicted mature height, but not in predicted mature height. Percentage of predicted mature height is a reasonably valid estimate of biological maturity status in this sample of youth football players.

Overweight and Obesity among Youth Participants in American Football

To estimate the prevalence of overweight and obesity among participants in youth American football 9 to 14 years of age. Cross-sectional, 653 boys, 8.7 to 14.6 years. Height and weight were measured; body mass index (BMI) was calculated. Overweight and obesity were defined by international (International Obesity Task Force [IOTF]) and United States (Centers for Disease Control [CDC]) criteria. Prevalence and 95% confidence interval were calculated. Player age, height, and weight and midparent height were used to predict mature height; current height was expressed as a percentage of predicted mature height as an estimate of maturity status. Overall 45.0% (41.2% to 48.9%) and 42.6% (38.8% to 46.5%) of players were overweight or obese by CDC and IOTF criteria, respectively. Prevalence was highest in early maturing boys. Based on position-activity at time of injury (n = 180), overweight and obesity were more common among offensive and defensive linemen. Overweight and obesity were more prevalent in youth football players than in national samples of American boys. Allowing for limitations of the BMI and the relative stability of the BMI from adolescence into adulthood, a relatively large number of football participants may be at risk for later overweight or obesity, and the risk appears to be greater for offensive and defensive line positions.