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Context: Among American sports, football has the highest incidence of exertional heat stroke (EHS), despite decades of prevention strategies. Based on recent reports, 100% of high school and college EHS football fatalities occur during conditioning sessions. Linemen are the at-risk population, constituting 97% of football EHS deaths. Linemen heat up faster and cool down slower than other players., Evidence Acquisition: Case series were identified from organized, supervised football at the youth, high school, and collegiate levels and compiled in the National Registry of Catastrophic Sports Injuries. Sources for event occurrence were media reports and newspaper clippings, autopsy reports, certificates of death, school-sponsored investigations, and published medical literature. Articles were identified through PubMed with search terms "football," "exertional heat stroke," and "prevention.", Study Design: Clinical review., Level of Evidence: Level 5., Results: Football EHS is tied to (1) high-intensity drills and conditioning that is not specific to individual player positions, (2) physical exertion as punishment; (3) failure to modify physical activity for high heat and humidity, (4) failure to recognize early signs and symptoms of EHS, and (5) death when cooling is delayed., Conclusion: To prevent football EHS, (1) all training and conditioning should be position specific; (2) physical activity should be modified per the heat load; (3) understand that some players have a "do-or-die" mentality that supersedes their personal safety; (4) never use physical exertion as punishment; (5) eliminate conditioning tests, serial sprints, and any reckless drills that are inappropriate for linemen; and (6) consider air-conditioned venues for linemen during hot practices. To prevent EHS, train linemen based on game demands., Strength-Of-Recommendation Taxonomy: n/a., Competing Interests: The following authors declared potential conflicts of interest: J.K.D. is an employee of the Gatorade Sports Science Institute, a division of PepsiCo. The views expressed in this article are those of the authors and do not necessarily reflect the position or policy of PepsiCo, Inc. R.C. is on the medical advisory board for BOA. J.K.D. has stock options from PepsiCo.

Background: A previous report revealed an average of 7.2 (0.67 per 100,000 participants) sport-related structural brain injuries (SRSBIs) with macroscopic lesions per year in high school (HS) and college football players. The Lystedt law and other rule changes have been implemented with intent to reduce the risk of brain injury in football., Hypothesis: To update the profile of SRSBIs in HS and college football players and evaluate the efficacy of legislation intended to reduce brain injuries., Study Design: Descriptive epidemiology study., Level of Evidence: Level 4., Methods: We retrospectively reviewed 18 academic years (July 2002 through June 2020) of SRSBIs catalogued by the National Registry of Catastrophic Sports Injuries. The incidence of SRSBIs was assessed at the HS level during the pre (July 2002 through June 2009), transitional (July 2009 through June 2014), and post (July 2014 through June 2020) universal adoption time periods of the Lystedt law. In addition, the incidence of SRSBIs during the second half of the study (2011-2012 through 2019-2020) was compared with the first half of the study (2002-2003 through 2010-2011)., Results: During the study period, there was a total of 228 SRSBIs (12.7 per year, 1.01 per 100,000 participants): 212 (93%, 11.8 per year, 1.00 per 100,000) in HS athletes and 16 (7%, 0.89 per year, 1.17 per 100,000) in college athletes. There were 52 fatalities (2.9 per year, 0.22 per 100,000 participants) with 46 (2.56 per year, 0.22 per 100,000) in HS athletes and 6 (0.33 per year, 0.43/100,000) in college athletes. There was no significant difference in risk of HS total SRSBIs or fatalities during the 3 Lystedt periods. The risk of combined SRSBI cases [relative risk (RR) = 1.22, P = 0.13] and fatalities (RR = 1.20, P = 0.52) was similar in the second half of the study compared with the first half of the study., Conclusion: Despite implementation of rule changes intended to reduce head injury, in particular the Lystedt law, the incidence of SRSBIs has remained unchanged. Further research is necessary to develop effective prevention programs for SRSBIs., Clinical Relevance: SRSBIs remain a persistent problem in HS and college American football. The recent head injury rule changes have not been effective at reducing SRSBIs.

Background: Nontraumatic fatalities occur on a regular basis in high school (HS) and college football athletes, primarily in obese linemen performing high-intensity exercise. One contributing factor to these deaths may be a mismatch between baseline aerobic (cardiorespiratory) fitness and exercise regimens., Hypothesis: There is a wide range of aerobic fitness in HS and college football players. Body mass index (BMI) is a safe and simple method for estimating baseline aerobic fitness., Study Design: Retrospective cohort study., Level of Evidence: Level 3., Methods: A retrospective review was performed on 79 HS football athletes who had VO 2Peak (mL·kg -1 ·min -1 ) measured during the offseason. Multivariate regression analysis was used to determine if BMI (obese, overweight, and normal; kg/m 2 ), position played (linemen vs other), year in school (freshmen vs other), and/or race (African American vs White) were risk factors for poor aerobic fitness. A separate cohort of 135 (48 HS; 87 college) football athletes performed a 6-minute run test to determine speed (miles/min), extrapolate VO 2Max , and calculate reference values for suggested upper threshold safe starting speeds (85% of maximum) for aerobic training based on BMI. The relationship between BMI and VO 2Peak was assessed. The exercise regimens (speeds) of 2 collegiate football fatalities from the public domain were used to predict their VO 2Max values., Results: Mean VO 2Peak (mL·kg -1 ·min -1 ) was 38.5 ± 8.6 (range 19.1-60.6); when grouped by BMI, low scores (<40) were found in 87.5% of obese (32.4 ± 7.7), 47.8% of overweight (40.8 ± 7.6), and 45.2% of normal (41.4 ± 7.8) athletes. VO 2Peak was significantly lower in linemen (32.8 ± 6.4; P = 0.007) compared with nonlineman (41.8 ± 7.9), and in obese players (by BMI; 32.4; P = 0.019) compared with nonobese players (41.4 ± 7.6), but did not differ by age, year in school, or race. Means for speed (min/mile) and extrapolated VO 2Max (mL·kg -1 ·min -1 ) for the 6-minute run test by BMI groups were both significantly different ( P = 0.001) for normal (7.0 ± 0.6; 51.1 ± 2.6), overweight (7.6 ± 0.8; 46.5 ± 3.2), and obese (8.9 ± 1.5; 36.8 ± 5.9) athletes. There was a significant negative correlation ( r = -0.551; P = 0.001; R 2 = 0.304) between VO 2Peak and BMI. Safe starting speed recommendations for running 1 mile range from 7.3 to 12.1 min/mile for BMIs 20 to 40 kg/m 2 for HS and college athletes. For the 2 fatalities (mean, BMI of 36.5 kg/m 2 ) repetitive sprint speeds were 49 and 89% higher than our safe starting speeds for their BMI., Conclusion: A large spectrum of baseline aerobic fitness was noted in HS and college football players. Obese players and linemen had statistically lower baseline aerobic fitness, a major risk factor for possible heat illness. BMI is an acceptable surrogate for VO 2Peak and can be employed to develop safe training regimens without the need for a maximum fitness test, which can place the athlete at risk for a medical event., Clinical Relevance: Knowledge of BMI provides an estimate of baseline aerobic fitness and a foundation for prescribing safe, individualized exercise regimens.

Background:: Cheerleading is a specialized athletic activity that can lead to catastrophic injuries. Cheerleading rules are in place to maximize safety of participants. The purpose of this study was to describe catastrophic cheerleading injuries among high school and collegiate-level participants in the United States and to explore whether the 2006-2007 basket toss rule change was effective at reducing the number of catastrophic injuries., Hypothesis:: The 2006-2007 basket toss rule change contributed to a reduction in the number of catastrophic injuries among high school and collegiate cheerleaders., Study Design:: Case series., Level of Evidence:: Level 4., Methods:: Data on catastrophic cheerleading injuries were collected by the National Center for Catastrophic Sport Injury Research from July 2002 to June 2017. Information collected included cheerleader, event, and injury characteristics. The impact of the 2006-2007 rule change banning the basket toss on any hard surfaces was assessed by comparing injury rates and 95% CIs before and after the rule change., Results:: There were 54 catastrophic cheerleading injuries, or 3.6 injuries per year. From July 2002 through June 2017, the injury rate was 2.12 per 1,000,000 cheerleaders (95% CI, 1.56-2.69). Most cheerleaders sustained serious injuries (n = 27; 50%) during practice (n = 37; 69%) to the head (n = 28; 52%) and cervical spine (n = 17; 32%). From July 2002 through June 2017, basket tosses were the stunt that accounted for the highest proportion of injuries (n = 19; 35%). The basket toss injury rate decreased from 1.55 to 0.40 per 1,000,000 cheerleaders among both high school and collegiate cheerleaders after the rule change., Conclusion:: Catastrophic injury rates in cheerleading decreased dramatically after the 2006-2007 rule change banning basket tosses from being performed on any hard surfaces. In particular, there was a nearly 4-fold reduction in the rate of catastrophic basket toss injuries.

Background: Patellofemoral pain (PFP) is a prevalent disorder among female adolescents. Overuse is frequently cited as the cause of pain for this population. What is currently unclear, however, is if the patella demonstrates abnormal tracking patterns relative to the femoral trochlear groove in female adolescents with PFP., Purpose: The aim of this case-control study was to determine if abnormal patellar tracking patterns are present in female adolescents with PFP. The secondary aim was to identify if an increased tibial tuberosity-trochlear groove (TT-TG) distance is associated with the observed kinematic patterns., Study Design: Controlled laboratory study., Methods: Twenty female adolescent knees from 12 patients with PFP and 20 age-matched female knees from 13 healthy controls were recruited for this study. Patellofemoral kinematics (eg, lateral patellar displacement) during a repetitive knee extension-flexion maneuver was quantified by dynamic cine phase-contrast magnetic resonance imaging (MRI). Static MRI scans were used to determine the TT-TG distance., Results: Relative to the control cohort, female adolescents with PFP demonstrated significantly greater lateral displacement at 10° (3.2 mm; P < .001), 20° (2.3 mm; P < .001), and 30° (1.7 mm; P = .014) of knee flexion. A subgroup within this cohort (7 knees from 5 patients) demonstrated extreme lateral maltracking >2 SDs of the mean of the control cohort. This subgroup also demonstrated a greater TT-TG distance relative to the controls (Δ = 4.2 mm; P = .001)., Conclusion: This study demonstrates abnormal lateral patellar displacement in the absence of patellar tilt in female adolescents with PFP. Because all adolescents from both cohorts participated in impact sports, it appears that rigorous athletic training alone is inadequate to produce symptoms in this population. Rather, PFP may derive from a combination of physical activity in the context of pathological kinematics., Clinical Relevance: Abnormal patellar tracking patterns and abnormal static alignment have been shown to contribute to the etiology of patellofemoral pain in adults. This study demonstrates that pathologic patellar tracking patterns are present in adolescent females with patellofemoral pain.

Background: Compressive and quadriceps forces have been associated with noncontact anterior cruciate ligament (ACL) injury. The purpose of this study was to quantify the relative importance of each load component during noncontact ACL injury., Hypothesis: We hypothesized that the introduction of a quadriceps force lowers the axial compressive force threshold to produce ACL injury., Study Design: Controlled laboratory study., Methods: Six pairs of fresh-frozen cadaveric knees, flexed to 15°, were loaded with axial compression (group A) or compression with a quadriceps force (group B) until failure. All specimens underwent axial compressive loading under displacement control with a time to peak load of 50 msec. The initial displacement of the MTS actuator was 8 mm and was increased in 2-mm increments with successive tests until catastrophic damage of the joint occurred. Failure was determined by a combination of clinical specimen examination and force-displacement data analysis and by dissection and direct visualization after failure was recognized. Differences in failure load between groups were examined using a paired t test (significance, P ≤ .05)., Results: In group A, there were 2 isolated ACL injuries, 2 ACL ruptures combined with a tibial plateau fracture, and 2 isolated tibial plateau fractures. In group B, there were 5 isolated ACL ruptures and 1 tibial plateau fracture. There was a significant difference in the average failure load between groups A and B: 10 832 N (95% confidence interval [CI], 9743-11,604 N) and 6119 N (95% CI, 4335-7903 N), respectively., Conclusion: Isolated compressive forces displayed an ability to produce an ACL injury in this cadaveric model, but the addition of a quadriceps load significantly reduced the compressive force required for ACL injury., Clinical Relevance: Compressive and quadriceps forces contribute to noncontact ACL injury and should be taken into account when developing ACL injury prevention programs and rehabilitation after ACL reconstruction.