American Football Research Articles

Abstract Repetitive head impacts are common in contact and collision sports and are linked to structural brain changes and an elevated risk of neurodegenerative diseases such as Chronic Traumatic Encephalopathy. Identifying early in vivo structural markers remains challenging. Although diagnosis currently requires postmortem confirmation, clinical symptoms, including cognitive impairment and behavioral changes, are reflected in the diagnosis of Traumatic Encephalopathy Syndrome. These symptoms align with dysfunction in key brain regions—amygdala, hippocampus, and thalamus—which support memory, emotion, and behavior, and commonly show tau pathology in Chronic Traumatic Encephalopathy. This study uses shape analysis to examine structural differences in these regions between former American football players and unexposed asymptomatic controls and evaluates the influence of age, head impact exposure, and clinical diagnosis on brain structure. We analyzed brain morphology in former American football players (n = 163) and unexposed, asymptomatic controls (n = 53). Structural segmentation was performed with FreeSurfer 7.1, and the shape analysis pipeline was used to generate subregional reconstructions. Vertex-level morphometry, based on the logarithm of the Jacobian determinant and radial distance, quantified local surface area dilation and thickness. Group differences were examined with covariate-adjusted linear regression models contrasting football players and controls, as well as participants with and without a Traumatic Encephalopathy Syndrome diagnosis. Partial correlations examined the influence of age, age of first football exposure, and cumulative head impact index metrics, including frequency, linear acceleration, and rotational force. Models were adjusted accordingly for age, body mass index, education, race, imaging site, apolipoprotein ε4 status, and total intracranial volume. Former football players exhibited bilateral surface area contractions in the hippocampus and amygdala, along with reduced amygdala thickness, compared to controls. Older age was associated with widespread surface contractions and thinning across all regions, except for preserved thickness in the left hippocampus. An earlier age of first exposure to football correlated with surface contractions in the thalamus and left hippocampus. Greater cumulative linear acceleration was linked to bilateral hippocampal surface contractions and reduced thickness in the left thalamus, while greater rotational force exposure was associated with hippocampal thinning. No significant structural differences were found between players with and without a diagnosis of Traumatic Encephalopathy Syndrome. These findings extend volume-based research by revealing localized alterations in surface area dilation and thickness and emphasize the roles of age and repetitive head impact exposure in long-term brain changes.

Years playing American football and primary playing position are often used to estimate concussion exposure. We examined associations between playing position and total years played with concussion history and neurobehavioral outcomes among former (N = 1544) National Football League players in the NFL-LONG study. Outcomes included the PROMIS Cognitive, Depression, and Anxiety T-scores, and Neuro-QOL Emotional-Behavioral Dyscontrol T-scores. Playing position was categorized as offensive/defensive linemen, running back/linebacker/tight end, quarterback/wide receiver/defensive back, and special teams. Analysis of variance tested differences between years played across position groups. Multivariable regressions estimated associations between years played, position group, and their interaction for outcomes, adjusting for covariates. There was no significant difference in years played across playing positions, and no statistically or clinically significant findings linking position, years played, or their interaction with negative neurobehavioral outcomes. These findings suggest concussion history should be directly assessed and considered alongside other exposure indicators to better understand neurobehavioral outcomes.

Local and global effects of inertial force components producing brain strain during head impacts.

Microbial skin infections are a major yet often underestimated concern in contact sports, posing health and performance risks for athletes. This narrative review examines the epidemiology, risk factors, and preventive strategies for three predominant infections—methicillin-resistant Staphylococcus aureus (MRSA), dermatophytic tinea, and herpes gladiatorum—across contact sports such as wrestling, rugby, mixed martial arts (MMA), and American football. Literature from PubMed and Web of Science, along with CDC and NCAA reports, was reviewed to assess infection prevalence and control measures. Wrestling showed the highest incidence of herpes gladiatorum, while rugby and football reported notable MRSA and tinea outbreaks linked to close physical contact and shared facilities. Key transmission factors include skin abrasions, inadequate hygiene, contaminated equipment, and inconsistent adherence to preventive guidelines. Effective prevention requires routine athlete screening, rigorous personal and environmental hygiene, targeted pharmacologic prophylaxis, and athlete education. Although existing guidelines from sports authorities provide valuable frameworks, gaps remain in standardization and implementation across sports. Future research should focus on antimicrobial resistance trends, rapid screening tools, and behavioral interventions to enhance compliance. Strengthening coordinated hygiene protocols and evidence-based preventive strategies is essential to safeguard athlete health and maintain competitive integrity.

(1) Background: This study examined the acute and chronic effects of sled-resisted training on power, strength, jump height (evaluated through a CMJ), and sprint kinematics in Spanish amateur football players. (2) Methods: A total of 19 football players (28 ± 8 years; 172 ± 12 cm; 79.3 ± 22.3 kg) performed 10 sled-resisted training sessions with loads of 80% (±2 kg) of their body mass on the day before the match (MD-1). Performance was assessed using a CMJ measured with the My Jump Lab app and sprint kinematics recorded with the 1080 Sprint system; both of these sensor-based technologies are validated for sports performance analysis. The CMJ was performed on MD-1 before the training and again on match day. Sprinting was evaluated before the sled-resisted training and again one week after it ended. (3) Results: These results suggest that sled training with heavy loads and low volume may not have acute effects on CMJ in amateur football players 24 h after it is performed, but there are chronic improvements in CMJ relative force and changes in sprinting after 10 weeks of sled-resisted training. (4) Conclusions: The findings of this study will enable football coaches and physical trainers to understand the changes in this training method to improve performance in amateur football players, using only three repetitions per player per week.

Tauopathies are a subgroup of neurodegenerative diseases pathologically typified as tau protein aggregate deposits in the brain, including Alzheimer's disease (AD) and chronic traumatic encephalopathy (CTE). AD is the most common cause of dementia, and CTE is a unique tauopathy affecting contact sports athletes, such as those active in American football and boxing, among others. It is revealed that the three-dimensional configurations of the protofibrils in AD and CTE-specific tau filaments are rather similar. Baicalein (BA) is a natural polyphenol extracted from Scutellaria baicalensis Georgia and was confirmed to disaggregate the preformed tau fibrils in vitro. However, the atomic effects and underlying mechanisms of BA on the AD- and CTE-specific tau protofibrils are largely unknown. In this study, we conducted all-atom molecular dynamics (MD) simulations on the two types of protofibrils without and with BA. The results revealed that BA could decrease the structural stability and reduce the β-sheet structure probability of the two types of protofibrils. BA extended the three-dimensional conformations of the AD-type protofibril in the vertical axis direction while it extended the CTE-type protofibril in the horizontal axis direction. BA preferentially bound with the β-sheet fragments of the two types of protofibrils through hydrophobic, H-bonding, and π-π stacking interactions, while the binding sites showed many differences. In addition, the cation-π interaction only existed between BA and the AD-type protofibril. Our work provides useful theoretical implications for the design of drugs to prevent or delay the development of AD and CTE.

Post-activation performance enhancement (PAPE) is an acute performance increase in voluntary exercises induced by a conditioning activity. Due to the scarcity of evidence about the effectiveness of distinct protocols, the aim of this study was to compare the effects of two different flywheel PAPE protocols (half-squat and lunge exercises) on vertical and horizontal jump performance, as well as change-of-direction ability in female amateur footballers (n = 21). Each protocol consisted of 3 sets of 6 repetitions for the half-squat protocol or 10 repetitions for the lunge protocol, with two minutes of passive rest, performed with a conical pulley. Both protocols were followed by rests of two, eight, and twelve minutes for repeated countermovement jump (CMJ), triple hop, and change-of-direction test (modified T-505) testing. The fixed-effect model 2-ways-repeated measures ANOVA showed that there was no significant interaction between time and exercises performed (p > 0.05). There was no significant relationship between exercise specificity and performance in sport-specific tasks. Our results suggest that, within this population, neither flywheel protocol provided measurable PAPE benefits across varied time windows. The findings underscore the importance of strength levels in achieving PAPE benefits and question the specificity of PAPE protocols to targeted sport performance outcomes.

This study was carried out to examine the relationships between the sources of stress and mental strength of football players. Football players who played in at least five matches in the 2021-2022 season of regional amateur and professional football leagues participated in the research. A total of 1040 football players, including 702 amateurs and 338 professionals, voluntarily participated in the study. In the study, “Football Coach Athlete Stress Scale” and “Football Media Stress Sources Scale” and “Mental Endurance Inventory in Sports” was used. The findings were first recorded in the SPSS program, and the significance level was accepted as 0.5. The average age of the amateur football players participating in the research is 22.98±4.99 years, the sports age is 10.91±4.19 years, the average age of the professional football players is 25.87±5.17 years, and the sports age is 14.51±3.87 years. A significant difference was found between the two football player groups in both age and sports age (p

Flag football's upcoming appearance at the Los Angeles 2028 Olympics highlights a period of unprecedented growth in the sport. U.S. youth participation climbed 38 percent from 2019 to 2022, surpassing tackle football among 6- to 12-year-olds, while girls’ high-school rosters more than doubled between 2023 and 2024. NAIA varsity status and the NCAA Emerging Sports for Women program now anchor a youth-to-college pathway. Flag football adoption is fueled by lower equipment costs, inclusivity, and a significant reduction in injury risk compared with tackle football. The flag football analytics landscape is nascent with significant opportunity for growth. Flag football thus offers a safer, accessible, and potentially data-rich alternative to traditional American football, poised for global expansion and continued scholarly study.

Glymphatic system dysfunction associated with player position in collegiate American football players: A DTI-ALPS study

Purpose Investment in sporting talents, particularly football, supports clubs to maintain their team-building model while promoting sporting and economic success. This is an integral aspect of how football clubs can sustain their financial streams in the dynamic football environment. This investment is missing in the context of juvenile football management, creating a huge monetary gap in youth football development in Ghana. The study investigates the financial performance and sustainability of juvenile football clubs in Ghana. Design/methodology/approach Data from 107 registered juvenile clubs across 6 prominent football regions in Ghana, and with independent samples, the Jonckheere–Terpstra test supported analysing the significant differences in revenue sources of these clubs. Findings Findings show that club owners contributed the most proportion to total revenue, while transfer fees constitute the second largest funding source for club activities. However, transfer fees (z = 2.477, p < 0.005) and sponsorship from other organisations (z = 3.340, p < 0.005) proved statistically significant to overall revenue. Sports equipment and transportation consumed a chunk of their budget. Inadequate financial support from the Ghana Football Association (GFA) and other stakeholders impedes their smooth operations. Research limitations/implications The revenue and expenditure measures in the questionnaire were expressed in relative terms, which only provide information about percentage contributions and proportions in an ordered categorical manner, not actual total values, and can be considered a limitation. A cross-sectional design was prioritised over a longitudinal design because it was the first of its kind in Ghana, researching the financial sustainability of amateur football clubs. Again, a number of juvenile clubs declined to participate in this study despite clear explanations of anonymity and assurances that it was for academic purposes. This could be a reflection of business culture of juvenile football clubs, which is a reluctance to discuss or show their financial information. Practical implications Clubs sustaining their revenue streams and becoming operational must create practical financial policies and structures that can support them to remain in business. They need the support of the GFA, government, corporate entities, communities and international bodies to drive that financial change for effective management of revenues in maintaining the status quo rather than being ruined. The results provide vital data and information for the National Juvenile Committee of the GFA to understand the challenges of clubs and take appropriate steps to address them for the promotion and development of the sport. Social implications Amateur clubs can capitalise on crowdfunding through active use of social media to reach out to their communities, ex-players and sympathisers via the digital space. The study's results and data can serve as important guides and useful documents for new investors venturing into the juvenile football space. This will contribute to improving financial stability and viability while minimising financial risks and avoiding future insolvency in managing amateur football clubs in Ghana. Originality/value In advancing knowledge on the subject, the study recommends that clubs strategically position themselves by improving their structures, community engagement and partnerships, embracing innovations and diversifying revenue sources through projects such as investing in farms, partnering with local companies and seeking professional advice on investment opportunities and business innovations. Club owners' inability to diversify their revenues pose a serious threat to their sustainability and waste of talent. This study adds to the scant literature on youth football management in developing countries.

Football, as a team sport, relies on a delicate balance where tactical cohesion and strategic play are as critical as physical prowess. While evidence suggests that European teams often display higher physical intensity, the tactical differences between European and American football are still not well quantified. The aim of this study is to conduct a comparative analysis of passing, possession, and goal-scoring dynamics in Euro 2024 and Copa America 2024. Data from 51 Euro matches and 32 Copa America matches, encompassing all game events with sub-second precision, were obtained from StatsBomb. Analyses were performed in MATLAB, with possession calculated as ‘pure possession,’ excluding inactive periods. Euro 2024 teams demonstrated significantly more total passes per match (, Cohen’s ), higher pass completion rates (, Cohen’s ), and longer possession sequences (, Cohen’s ). They also showed greater possession in the five minutes prior to goals (, Cohen’s ). In contrast, Copa America 2024 teams favored longer passes (, Cohen’s ), reflecting a more direct playing style. Possession disparities between teams in individual matches did not differ significantly (, Cohen’s ), and the distribution of shot distances for goals was also similar across tournaments (, Cohen’s ). In summary, Euro 2024 teams emphasized control through longer possession and greater passing accuracy, while Copa America 2024 teams relied on more dynamic and direct play. These findings underscore how regional footballing philosophies shape match strategies and outcomes, offering insights into the tactical diversity of international football.

ABSTRACT This study collected the first direct measurements of the kinetic and kinematic variables associated with initial acceleration performance in American football players. 123 male NCAA Division I American football players performed one-to-two maximal sprints of 20–30-meters. Kinetics were derived from a linear motorised encoder and individual linear sprint force-velocity-power (FVP) profiles were calculated utilising a validated field method. Kinematics were derived from video images recorded in slow-motion. The first three steps, including the initial push-off, were used for analysis at the instants of toe-off and touchdown. Large to nearly perfect, significant relationships were obtained between maximal power and 10-meter time. The spatiotemporal variables with the strongest relationships to maximal power were contact time, takeoff and step velocity, and normalised flight length. At toe-off, the swing leg hip angle, stance leg thigh angle, and CM-toe distance had large relationships with maximal power. At touchdown, the shank angles of both the stance and swing leg and the stance leg knee angle had large relationships. Maximal power associated with force output in the horizontal direction may considered a key performance indicator for initial acceleration in American football and certain technical underpinnings are associated with higher levels of maximal power during initial sprint acceleration.

Abstract Objectives The effect of attentional focusing on muscular activities and motor skills has been well established. It is known that internal focusing (on body movement or the action itself) results in increased muscular activity. However, external focusing (on apparatus or the effect of action) results in decreased motor responses. In this study, the impact of attentional focusing has been investigated by exploring the three major components of hamstrings: the semitendinosus, the semimembranosus and the biceps femoris via EMG activity on 20 amateur football players during leg curl exercises. Methods To measure muscle activities of the participants, Integrated EMG (IEMG) was calculated on the data’s MVC values. Paired sampled t-tests with Bonferroni correction (α=0.0167) were performed on the average IEMG values to determine if there is a significant difference between participants’ muscles activities under various attentional focus conditions. Results The results showed that the semimembranosus exhibited significantly reduced activity under both external (p=0.0124) and internal focus (p=0.0008), while the semitendinosus displayed a small but non-significant reduction under external focus (p=0.0355 > 0.0167). The biceps femoris showed no significant motor response regarding change between attentional focus instructions. Conclusions This study improves understanding of the mind-muscle connection by showing muscle-specific differences in attentional focus effects, with semimembranosus being most responsive.

Abstract: The research focuses on using the YOLOv8 model to detect and analyze neck rotation following head collisions in order to propose preventive healthcare treatments. The location and orientation of the neck must be measured and monitored in order to predict its trajectory during such impacts. The experiment, which replicates movements like flexion and lateral rotation based on American football scenarios and simulates minor head hits, will involve ten volunteers—five male and five female. The research focuses on using the YOLOv8 model to detect and analyze neck rotation following head collisions in order to propose preventive healthcare treatments. The location and orientation of the neck must be measured and monitored in order to predict its trajectory during such impacts. The experiment, which replicates movements like flexion and lateral rotation based on American football scenarios and simulates minor head hits, will involve ten volunteers—five male and five female. Keywords: Yolov8, Trajectory, Flexion.

ObjectiveAnkle sprains are one of the most common injuries sustained by American football athletes. Players with a recent history of ankle sprain, even when asymptomatic, may have sensorimotor impairments that affect control of the hip and knee during dynamic activities such as speed running. Among players preparing for the National Football League (NFL) draft, these functional deficits have wide-ranging effects and warrant systematic investigation. This study aimed to determine the influence of a recent history of ankle sprain (≤6 months) and a six-week NFL draft preparation training camp on hip-ankle (HA) and knee-ankle (KA) coordination. Specifically, we examined HA and KA coordination angles and variability using vector coding. We hypothesized that the group with a recent ankle sprain history (RASH) would express less ankle-dominant patterns, and these would improve post-training, and the RASH group would show impaired neuromuscular adaptability as evidenced by lower coordination variability, but this would improve post-training, through increased variability.Materials and methodsThis study analyzed a sample of 12 athletes with a recent ankle sprain history (RASH) and compared their running mechanics to 12 matched controls with no recent ankle sprain history (non-RASH). Running mechanics during a five-second 23 km/h run were evaluated pre- and post-training using a 10-camera motion capture system. Coordination was quantified into angles using vector coding, and coordination variability was quantified using circular statistics, with variability expressed as the standard deviation derived from the mean resultant length of angular data. Data for both were derived over four subphases of the running gait cycle: first half stance, second half stance, first half swing, and second half swing. A 2 (RASH and non-RASH) × 2 (pre and post) ANOVA were used to assess the influence of ankle sprain history and training on HA and KA coordination and coordination variability (p ≤ 0.05).ResultsNo significant group × time interactions or main effects were found in any of the subphases for coordination angles or variability for HA and KA (p > 0.05). For HA, there were medium effect sizes in coordination angle for the second half of stance (η²ₚ = 0.075) and coordination variability for the second half of swing (η²ₚ = 0.121). The RASH group had larger increases in HA angle from training (212.7 ± 102.7° (pre) versus 235.5 ± 91.2° (post)) than the non-RASH group (268.7 ± 56.8° (pre) versus 265.5 ± 48.2° (post)). Further, the RASH group shifted from an in-phase hip-dominant to an in-phase ankle-dominant pattern in the second half of stance. For KA, there were medium effect sizes for the first half stance (η²ₚ = 0.093) and second half swing (η²ₚ = 0.091). Specifically, for the first half stance, the RASH group changed from anti-phase ankle to in-phase ankle control (97.0 ± 19.5° (pre) versus 85.5 ± 29.4° (post)), while the non-RASH group was stable at an anti-phase ankle pattern (93.6 ± 19.8° (pre) versus 95.6 ± 19.8° (post)). For the second half swing, both groups produced in-phase knee-dominant patterns, but the RASH group decreased their coordination angle by 4.4°, and the non-RASH group increased their coordination angle by 3.8°.ConclusionsHighly skilled athletes with a recent history of ankle sprains adopt compensatory joint coupling strategies that persist even in the absence of symptoms and can be modified through training.

Background/Objectives: National Football League (NFL) American football players are exposed to osteoarthritis risk factors of obesity and high joint loads. We sought to examine the association between total body mass (TBM), lean body mass (LBM), body fat percentage (BF%), and normalized compressive knee joint reaction forces (JRFcomp), peak knee adductor moments (KAM), and vertical ground reaction forces (vGRF) in NFL draft-eligible players during a high-speed run. Methods: A total of 125 participants ran a single trial at 5.5–6.5 m/s for 5 s on an instrumented treadmill. Bilateral vGRF and knee joint kinetics were calculated using inverse dynamics. Body composition was assessed using bioelectrical impedance. Results: LBM demonstrated significant moderate associations with vGRF (left, r(123) = −0.56, p < 0.001; right, r(123) = −0.60, p < 0.001) and low-to-negligible associations with KAM (left, r(123) = −0.20, p = 0.026; right, r(123) = −0.30, p < 0.001) and JRFcomp (left, r(123) = −0.39, p = 0.020; right, r(123) = −0.38, p = 0.015), respectively. TBM showed significant moderate negative associations with vGRF (left, r(123) = −0.56, p < 0.001; right, r(123) = −0.61, p < 0.001) and low-to-negligible associations with KAM (left, r(123) = −0.21, p = 0.021; right, r(123) = −0.28, p = 0.002) and JRFcomp (left, r(123) = −0.39, p < 0.001; right, r(123) = −0.37, p < 0.001), respectively. BF% showed significant low-to-negligible negative associations with JRFcomp (left, r(123) = −0.21, p < 0.001; right, r(123) = −0.22, p < 0.001) and vGRF (left, r(123) = −0.39, p < 0.001; right, r(123) = −0.41, p < 0.001), respectively, and no significant associations with KAM, p > 0.05. The heavier group exhibited significantly lower normalized JRFcomp, and vGRF, p < 0.05. Conclusions: Heavier, but not fatter, players attenuate knee loads. Dampening may be a short-term protective strategy for joints of heavier players.

A growing body of evidence suggests that repetitive head acceleration events (HAEs), even in the absence of diagnosed concussion, could have implications for long-term neurological function. This study aims to determine the on-field validity of instrumented mouthguards (iMGs) in American football and to quantify HAE incidence in NCAA football players. Instrumented mouthguards were fitted to 35 male NCAA football players. Head kinematic data were collected during 68 player matches. On-field validity was determined through video review with positive predictive value (PPV) and sensitivity values calculated. HAE incidence was calculated as the number of HAEs per player match and stratified by Offense and Defense positions. On-field validity of the Prevent Biometrics iMG in NCAA American Football indicates a sensitivity of 0.89 and PPV of 0.98 based on false positive definitions. The mean incidence of HAEs above a range of peak linear acceleration (PLA) and peak angular acceleration (PAA) thresholds in Defense and Offense appear similar. The incidence of HAEs above 10 g was 11.2 and 11.3 HAEs per player match for Defense and Offense, respectively, while PAA incidence above 1.0 krad/s 2 was 5.5 and 6.9 HAEs per player match for Defense and Offense, respectively. Incidence of HAEs above 30 g was 1.6 and 2.6 per player match and 0.9 and 1.4 for HAEs above 2.0 krad/s 2 for Defense and Offense, respectively. The Prevent Biometrics iMG appears suitable for measuring HAEs in elite American football and benchmark HAE incidence in elite American Football lays a foundation for the development HAE mitigation strategies.

This study examined the efficacy of resistance training utilizing a novel bench press pad (BPAD) to improve performance in the one-repetition maximum (1-RM) bench press, the National Football League (NFL) 225-lb reps to-fatigue bench press test (NFL-225 Test), and a seated medicine ball throw (SMBT) following an 8-week, two-block periodized bench press training program. Thirty male collegiate football players with a history of moderate resistance training were randomized to one of two groups, each utilizing either a novel bench press pad or traditional flat bench (CONT). The participants exercised thrice weekly for eight weeks (totalling 24 sessions) while also participating in a simultaneous 8-week off-season training program. The bench press exercises were incorporated into the regular 1-hour sessions occurring three times per week and divided into two identical block periods, which differed only in the equipment used. The training session comprised three chest press exercises, upper and lower chest presses, as well as fly exercises, which enabled the application of different variations of external loads to the pectoral muscles. Both groups exhibited significant improvements in 1-RM BP, NFL-225 Test, and SMBT after 8 weeks (all p < .001), with the BPAD group demonstrating a significantly greater increase compared to the CONT group in all performance outcome measures (all p < .001). These results suggest that the use of a BPAD intervention may provide an additive effect to bench press training, which can elicit greater upper body strength, power and performance enhancements.

The sports analytics industry has seen a rapid influx of data, driving widespread adoption of machine learning for predictive analytics. However, this shift has often sidelined conceptual understanding and explainability. Focusing on pass completion prediction in American football, we develop transparent models matching black-box performance. In this work, we use pass completion prediction as a case study and build explainable models that achieve comparable performance to black-box approaches when trained on spatio-temporal features. Our approach involves two key strategies: first, developing a conceptual understanding to engineer a small explainable feature set; second, leveraging this understanding to create a physics-based probabilistic model as a single equation. Surprisingly, both logistic regression and the transparent model achieved 72% accuracy, matching complex models. Using the small explainable feature set, an ensemble model reached 78% accuracy, outperforming the state of the art while maintaining interpretability. Beyond prediction, explainable models provide actionable insights into play dynamics, player performance, and training strategies. In contrast, black-box models, while potentially improving prediction accuracy, obscure which features contribute to predictions, how they interact, and why specific outcomes occur. This lack of transparency limits their ability to inform decision-making and guide future investigations.