The effects of 40-, 60- and 90-minute nap durations on physical and physiological performance after sleep deprivation: A experimental study on male university soccer players

The link between repetitive head impact (RHI) exposure, later-life cognitive decline, and neurobehavioral dysregulation (NBD) is not well understood. Recent work has implicated inflammation and limbic dysfunction as relevant RHI correlates. Our goal was to integrate plasma and CSF inflammatory biomarkers, structural brain imaging, and clinical measures in former elite American football players to better understand reasons for RHI-related cognitive and neurobehavioral changes. Participants were from the Diagnostics, Imaging, and Genetics Network for the Objective Study and Evaluation of Chronic Traumatic Encephalopathy Research Project, which recruited male former college/professional football players with RHI and asymptomatic unexposed (UE) controls with no history of contact sports, military combat, or traumatic brain injury/concussion. Our study focused on plasma/CSF inflammatory biomarkers (interleukin [IL]-6, tumor necrosis factor [TNF]-α, glial fibrillary acidic protein), limbic white matter (WM) microstructure (diffusion tensor imaging: fractional anisotropy [FA], mean diffusivity [MD]), and clinical measures (memory, executive function, NBD). Hierarchical linear regressions assessed change in variance explained (ΔR2) among inflammation, WM, and clinical outcomes in former football players. Post hoc analyses tested whether associations differed by group (football vs UE; group interactions) or were stronger in football players considered at highest risk of CTE. Our sample included 223 men (n = 170 football players: age 57.2 ± 8.1 years, 33% non-Hispanic/Black; n = 53 UE participants: age 59.4 ± 8.6 years, 34% non-Hispanic/Black). In football players, higher inflammation was associated with lower limbic FA (plasma IL-6: ΔR2 = 0.03 [0.001-0.09], p = 0.03; CSF IL-6: ΔR2 = 0.03 [-0.01 to 0.11], p = 0.03; plasma TNF-α: ΔR2 = 0.05 [0.01-0.11], p = 0.003) and higher limbic MD (CSF IL-6: ΔR2 = 0.06 [0.007-0.15], p = 0.01). Inflammation was more strongly related to limbic WM microstructure in football players than in UE participants. Worse WM microstructure was associated with worse memory in football players (FA: ΔR2 = 0.05 [0.003-0.14], p = 0.007; MD: ΔR2 = 0.07, p = 0.003 [0.008-0.16]). Most of the observed associations were stronger in the CTE probable subgroup. There were no direct associations between plasma or CSF markers of inflammation and cognition. In former elite football players, elevated plasma and CSF inflammatory markers were associated with poorer limbic WM microstructure, which in turn related to worse cognition. Given the limbic system's role in cognition and behavior, inflammation may be a modifiable target for RHI-related neurodegeneration. Limitations include the cross-sectional design and limited generalizability to other contact sports, lower levels of play, female athletes, or other RHI sources.

Effects of adding thoracic spine exercises to routine soccer training on spinal alignment and mobility in professional male soccer players: a randomized controlled study.

QRS fragmentation (fQRS) and low QRS voltage are electrocardiogram (ECG) findings associated with cardiomyopathy and adverse cardiac events. However, their prevalence and significance in elite female athletes are unknown. The aim of this study was to determine the prevalence and clinical significance of fQRS and low QRS voltage in elite female footballers undergoing cardiovascular screening. Between April 2017 and October 2024, a cohort of 2,566 consecutive elite female football players underwent cardiovascular screening, including a 12-lead ECG and echocardiogram. ECGs were analysed for the presence of fQRS and low QRS voltage. These findings were correlated with demographic and echocardiographic data. The mean follow-up period was 4.4 ± 2.5 years. The mean age was 20.13 ± 5.48 years. fQRS in ≥2 contiguous leads was present in 205 (8.0%) athletes, predominantly in the anterior leads (61.3%). fQRS in lead V1 alone was seen in 370 (14.4%) players. Athletes with fQRS demonstrated significantly larger indexed right ventricular (p < 0.001) and left ventricular (p = 0.033) diameters compared to those without. Low QRS voltage in the limb leads was exceedingly rare, observed in only 2 (0.1%) athletes. No athlete was diagnosed with cardiomyopathy. In elite female footballers, fQRS is a common ECG finding strongly associated with physiological biventricular remodelling, particularly of the right ventricle. Within the context of this screening programme, fQRS was not associated with detectable cardiac pathology or adverse events, suggesting it may represent a feature of the athlete's heart rather than underlying disease. Conversely, the extreme rarity of low QRS voltage suggests it warrants clinical suspicion if detected. These sex-specific findings provide a new reference for interpreting ECGs in this unique population.

ABSTRACT This study examined whether different sports (athletics, football, rugby, handball) influence sprint performance and force-velocity-power (F-v-P) profiles according to maturity status. 120 male youth (30 per sport; aged 12.0–16.9 years), matched for chronological age and maturity offset (MO), performed two maximal 30-metre sprints. Sprint performance and F-v-P variables (F 0, v 0, P max, S FV) were calculated using Samozino’s method from radar-derived velocity-time data and photocell splits. ANCOVA and regression analyses assessed the effects of sport, maturity, and their interaction. Significant main effects were observed for Sport and MO on all sprint performance variables (p < 0.05 to p < 0.001). Football and rugby players were faster than handball players and track sprinters over 10 metres, with football players fastest at 30 metres. MO × Sport interactions showed that football players had smaller sprint gains with maturation. A significant main effect of Sport was revealed for all F-v-P variables except for absolute P max (p < 0.01 to p < 0.001). Handball players showed the most force-oriented profile, differing from football and rugby players. Maturation-related improvements in F-v-P variables were similar across sports. These results suggest that while F-v-P development is mainly driven by maturation, sprint performance is more influenced by sport-specific demands.

ABSTRACT This paper explores an understudied area of soccer development: the minor league or semi-professional level. As North America prepares to host the 2026 Men’s FIFA World Cup, the impact of the minor league/semi-professional level towards respectability is studied through three qualitative methods: self-ethnography of the present author as a former semi-professional soccer player, informal interviews with other semi-professional and professional players, and descriptive statistics of the 2022 United States’ Men’s National Team (USMNT) and the 2022 Canadian Men’s National Team (CMNT). Of the 52 players on the 2022 USMNT and CMNT World Cup squads, 27 of them played in the minor league/semi-professional system of North America – as such, the development of players between the youth, collegiate and professional levels is important in creating players for both national teams.

ABSTRACT Fan zones have become an integral feature of major football tournaments, including the FIFA World Cup, providing spaces for collective viewing, entertainment, and commercial activity. This paper examines how fan zones can balance fan engagement, safety, and profitability. Using the Bolton Wanderers Football Club fan zone (2022–2023) as a case study, the study identifies practical lessons in spatial design, behaviour management, and the creation of inclusive atmospheres. Although based on a club-level example, the analysis considers how these insights can inform planning for FIFA World Cup 2026 fan zones across the United States, Canada, and Mexico. Particular attention is given to issues of proportional security, crowd behaviour, and the risks of excessive commercialisation. The findings suggest that well-designed fan zones can strengthen collective identity and contribute to event legacy, indicating that community-centred approaches may enhance the experience and inclusivity of large-scale international tournaments.

Introduction: Anterior cruciate ligament (ACL) injuries in soccer players are multifactorial in nature, and the evaluation of isolated predictors (such as the isokinetic hamstring-to-quadriceps [H/Q] ratio) shows limitations in identifying risk profiles. Therefore, the integration of multiple neuromuscular variables into a predictive model is proposed to overcome these inconsistencies and improve injury risk screening. Objective: To analyze the association between neuromuscular imbalances, functional asymmetries, and performance parameters in jump tests with the risk of ACL injury in soccer players, and to develop a multivariable predictive model capable of identifying clinically relevant risk profiles. Methods: A cross-sectional study with an analytical approach was conducted with 60 male soccer players aged 18–28 years. Isokinetic strength (60°/s and 180°/s), concentric and eccentric H/Q ratios, peak power, reaction time, and jump performance (CMJ, SJ, DJ, and RSI) were assessed. Inter-limb asymmetries were calculated, and their association with confirmed history of ACL injury was analyzed using Pearson correlation and multivariable logistic regression. Results: The predictive model revealed that an eccentric H/Q ratio &lt;0.85 (OR = 5.9), DJ asymmetry &gt;10% (OR = 4.1), CMJ power &lt;45 W/kg (OR = 2.4), and reaction time &gt;130 ms (OR = 1.9) significantly increased the risk of ACL injury (AUC = 0.88; accuracy = 85.3%). Conclusion: The multivariable model confirms that ACL injury risk results from the convergence of eccentric deficits, functional asymmetries, and impaired neuromuscular control. The integration of these variables is essential for accurate risk screening.

Unified Sports within Special Olympics aims to promote inclusion, where athletes with intellectual and developmental disabilities train and compete together with partners who do not have a disability. However, little is known about the health-related physical fitness (HrPF) of these athletes and partners. The primary objective of this study was to describe the HrPF of participants in the 2022 Unified Cup. Measures of HrPF were collected during Healthy Athletes Screenings from 201 soccer players, including 106 athletes and 95 partners. Notable differences were observed between athletes and partners in calf flexibility, timed sit-to-stand, and partial sit-up measures of HrPF (p < .001). In addition, hamstring flexibility and seated push-up showed notable differences between genders (p < .001). This study adds to the literature by utilizing the Healthy Athletes Screenings database. Results should be considered by coaches and programmers when working with Unified athletes in competitive settings.

This study investigates the performance characteristics of U18 semi-professional soccer players by examining both technical load (TL) and physical load (PL) variables across various playing positions during the 2021/2022 Spanish Football U18 National League Championship. Methods: Principal Component Analysis (PCA) was employed to simplify the dataset, which comprised 246 match records from 49 athletes (mean age 17.9 ± 0.7 years; height ~177.6 ± 6.3 cm; body mass ~72.0 ± 7.2 kg) across ten matches. This analytical approach aimed to facilitate a deeper understanding of player performance dynamics. Results: Kaiser–Meyer–Olkin (KMO) values varied across positions (technical load: 0.20–0.93; physical load: 0.27–0.91). This indicates acceptable sampling adequacy for several positional models, but low adequacy for others; therefore, results for positions with low-KMO values should be interpreted cautiously. Factor analysis for both technical and physical load variables identified two components each, explaining substantial total variance (technical load: 63.75–86.65%; and physical load: 71.74–88.92% across position), with significantly high factor correlations (p &lt; 0.001). The findings further indicate that players occupying defensive positions, such as goalkeepers and center-backs, generally exhibit lower levels of physical intensity and technical engagement compared to their counterparts in more dynamic roles, including full-backs, wingers, and forwards. The latter groups demonstrate higher involvement in high-intensity running and offensive actions. Conclusions: The observed performance patterns highlight the necessity for tailored training programs that align with the specific demands of each playing position. This approach is expected to optimize individual player performance and enhance overall tactical efficiency. Furthermore, the study underscores the importance of developing individualized conditioning strategies that address the unique physical and technical requirements inherent to each role on the field. This analytical approach using PCA provides a more structured and data-driven understanding of these positional differences, reinforming the need for tailored training programs and individualized conditioning strategies.

Retraction Note: An image classification algorithm for football players’ activities using deep neural network

Introduction: Anxiety plays a crucial role in affecting athletes' performance and well-being, particularly in high-pressure sports like football. While much research has focused on pre-competition anxiety, less attention has been given to how anxiety fluctuates after competition and the role of mental health support in addressing these changes. Objective: This study aims to investigate the anxiety levels of football players before and after a match, using a 16-item Likert scale to measure cognitive and somatic anxiety. The objective is to understand how anxiety levels change and explore the role of psychological support in managing anxiety. Results: The results show a significant reduction in anxiety levels, with the pretest average being 70.81 and the posttest average dropping to 47.63. The paired samples t-test confirmed a statistically significant decrease in anxiety (t = 18.92, p &lt; 0.001). However, there was increased variability in posttest anxiety, suggesting individual differences in how athletes cope with stress. Discussion: The findings suggest that anxiety decreases after a match, likely due to the relief of competition ending. However, the variability in post-match anxiety highlights the need for personalized psychological support, such as counseling, to help athletes manage residual stress. Conclusions: This study emphasizes the importance of mental health support for athletes before and after competitions. Tailored psychological interventions can help manage anxiety and improve athletes' overall well-being and performance.

The segmental dynamics of the lower leg in the side-volley kick in male soccer players.

This scoping review aimed to map and summarise the literature examining how different small-sided games (SSG) training regimens affect physical, psychophysiological, technical, and tactical outcomes in soccer players. The methodology followed the PRISMA-ScR guidelines, where three databases were searched. Eligible studies directly compared at least two SSG regimens (continuous vs intermittent; intermittent formats with differing work durations; or intermittent formats with differing rest durations). In total, 30 studies were included. Across the comparison types assessed, continuous vs intermittent regimens were the most studied, particularly for physiological measures (&lt;i&gt;n&lt;/i&gt; = 15), followed by intermittent comparisons manipulating bout duration (&lt;i&gt;n&lt;/i&gt; = 15 for physiological, &lt;i&gt;n&lt;/i&gt; = 11 for physical outcomes). Studies focusing on rest/density manipulations were fewer, especially for technical outcomes (&lt;i&gt;n&lt;/i&gt; = 3). Most studies clustered around mid-sized SSG formats (3v3–5v5), with 4v4 particularly dominant in continuous–intermittent contrasts (&lt;i&gt;n&lt;/i&gt; = 9). In contrast, very small-sided formats (1v1, 2v2) and larger-sided formats (6v6, 7v7) were rarely explored under these regimen conditions. Shorter bouts tended to increase external intensity per unit time and total distance, while fractionating continuous play into sets generally raised per-minute intensity and high-speed actions but reduced total volume. In small formats, continuous play tended to elicit higher heart rate, lactate, and enjoyment, though one study suggested females preferred intermittent, whereas males reported greater enjoyment and load with continuous play. Rest duration also appeared to modulate outcomes, with very short recoveries linked to reduced passing success and longer rests enabling better ball actions. In conclusion, current evidence is largely focused on physical and psychophysiological responses, while technical and especially tactical domains remain underexplored. To better inform training design, future research should aim to incorporate objective assessments of technical and tactical outcomes – using objective tools – while also extending to female players, elite levels, and longitudinal designs. These steps would help determine whether the acute responses mapped here translate into consistent adaptations across contexts.

Retraction Note: Analyzing the feature extraction of football player’s offense action using machine vision, big data, and internet of things

The aim of the research was to analyse the effect of stretching exercises on the reduction of muscle shortening in two single-group, time-nonconcurrent experiments conducted with female football players from the clubs MŠK Žilina (E1) and AFK Slávia Malešice (E2). The research sample consisted of 32 female football players (n = 32) with a decimal age of 25.23 ± 4.82 years. The occurrence of shortened muscles and muscle groups was assessed using standardized tests. The baseline examination identified five muscle groups with the highest prevalence of shortening, for which a specific set of stretching exercises was subsequently designed. The experimental intervention consisted of ten stretching exercises, with two variants proposed for each muscle group. The exercises were systematically integrated into training sessions over an eight-week period. The most frequently shortened muscles included the rectus femoris muscle, pectoralis major muscle, hip adductors, triceps surae muscle, knee flexors, and the erector spinae muscle. After completion of the intervention program, a follow-up assessment was conducted, which demonstrated a positive effect of the stretching exercises on reducing the prevalence of shortened muscles. In group E1, statistically significant changes were observed at the significance level p &lt; 0.01 for the hip adductors and the triceps surae muscle. At the significance level p &lt; 0.05, a significant change was recorded for the rectus femoris muscle. In group E2, statistically significant changes at p &lt; 0.01 were found for the rectus femoris and triceps surae muscles, while significance at the p &lt; 0.05 level was demonstrated for the hip adductors and the erector spinae muscle. The results of the analysis confirm that systematic targeting of shortened muscle groups through a focused stretching intervention aimed at specific muscles leads to a statistically significant reduction in muscle shortening and has a positive effect on muscular balance.

Assessment of somatotype represents an important tool in sports for the individualization of the training process and the optimization of performance, as it reflects the morphological predispositions of athletes. The aim of this study was to analyze the somatotype of male recreational and club athletes across various disciplines (football, rugby, baseball, running) and to determine the influence of sport specialization, age, and selected anthropometric characteristics on its individual components. Measurements were conducted on a sample of 73 subjects using standardized anthropometric procedures, and somatotype was determined using the Heath–Carter method by two approaches: calculation based on equations and assessment using the evaluation form. The obtained values were subsequently visualized using a somatograph. The analysis revealed significant differences between sports: football players showed an endomorphic mesomorph profile, rugby and baseball players demonstrated a predominance of the mesomorph-endomorph type, and recreational runners exhibited increased ectomorphy. With increasing age, an increase in endomorphy and a decrease in mesomorphy were observed. The study also confirmed the higher accuracy and time efficiency of the equation-based method compared to the form-based evaluation. The results highlight the importance of somatotype as a diagnostic tool applicable in the selection of sports disciplines, the adjustment of training load, and the monitoring of changes in athletes’ body composition.

Introduction: The distinct physical and tactical roles of American football positions may influence interlimb symmetry of ankle, knee, and hip power distribution during high-speed running. This study examined differences in joint power distribution symmetry between position groups and joints using inverse dynamics. Methods: Sixty-eight draft-eligible American football players (Big n=18; Big-skill n=24; Skill n=26) completed a single high-speed running trial (6.4 m/s) on an instrumented treadmill synchronized with a motion capture system. Joint powers were computed via inverse dynamics and expressed as positive (generation) and negative (absorption) percent contributions to total limb power. Interlimb differences were quantified using the Asymmetry Index (AI = |left−right|/[(left+right)/2] ×100%). Group differences were analyzed using Kruskal-Wallis tests with Bonferroni-adjusted post hoc comparisons (α = .017). Results: No significant differences in AI were found among position groups for positive ankle (p = .868), knee (p = .082), or hip power (p = .846), nor for negative ankle (p = .222), knee (p = .181), or hip power (p = .496). AI differed significantly among joints for both positive (F(2,134)=33.4, p&lt;.001, η²=0.332) and negative power (F(2,134)=15.7, p&lt;.001, η²=0.19). Knee AI was highest for positive power (31.9 ± 24.5%), followed by hip (18.1 ± 28.9%) and ankle (9.6 ± 6.9%). Negative AI was lowest at the ankle (11.9 ± 14.1%) compared to knee (22.4 ± 16.6%) and hip (22.8 ± 19.5%). Conclusions: Player position does not influence the symmetry of joint power contributions during high-speed running. The ankle demonstrates the greatest symmetry, whereas the knee shows the largest asymmetry.

Primary cam and pincer type morphology of the hip can lead to femoroacetabular impingement and osteoarthritis. This study aimed to assess and compare magnetic resonance imaging (MRI)-based radiological parameters of hip morphology between young male semi-professional soccer players and non-athlete controls. This observational cross-sectional study included a retrospective review of MRI scans of young male soccer players and an age- and sex-matched control group obtained from a hospital radiology database. Lateral center edge angle, acetabular version, alpha angle, collodiaphyseal angle, and femoral head coverage ratio were recorded and compared between groups. Bilateral hip MRI scans of 30 young male soccer players and 30 non-athletes were analyzed. The mean age of participants was 24.88±5.10 years (range, 15-34 years). In the non-athlete control group, anteversion was higher in both hips (P=0.02 for right hip and P=0.05 for left hip) and reached statistical significance for the right hip. The collodiaphyseal angle was higher in the soccer-player group (P=0.01 for the right hip and P=0.03 for the left hip). The femoral head coverage ratio was significantly higher in the control group (P=0.02 for the right hip and P=0.01 for the left hip). No significant difference was observed in lateral center edge angle or alpha angle between groups. Differences in collodiaphyseal angle, acetabular anteversion, and femoral head coverage ratio indicate partial variation in femoroacetabular morphology between groups; however, no evidence showed a higher incidence of cam or pincer morphology in soccer players.

Background:Frequent pivoting, rotation, and deep hip flexion place football players at high risk for femoroacetabular impingement (FAI), a leading cause of hip pain in this population. Previous studies have primarily focused on professional National Football League athletes undergoing mixed surgical techniques, including labral debridement. Limited data exist on outcomes in younger, amateur players treated with labral repair.Purpose:To report return to sport (RTS) rates and functional outcomes at a minimum 5-year follow-up in primarily active high school and college football players undergoing primary hip arthroscopy with labral repair for FAI.Study Design:Case series, Level of evidence, 4.Methods:All football players who underwent primary hip arthroscopy with labral repair for FAI between 2010 and 2019 were identified from an institutional database. Collected data included descriptive data, radiographic parameters, surgical details, and reoperations. At a minimum 5-year follow-up, RTS outcomes and patient-reported outcome measures (PROMs), such as the Modified Harris Hip Score (mHHS) and Hip Outcome Score (HOS), were evaluated.Results:A total of 36 hips in 27 male athletes (mean age, 18 years; body mass index, 28.1 kg/m2) were included. The majority of athletes competed at the high school (70%) or collegiate level (26%). Mean preoperative radiographic measurements were as follows: lateral center-edge angle, 31.6°; Tönnis angle, 4.1°; and alpha angle, 61.4°. Femoroplasty and acetabuloplasty were performed in 100% and 86% of cases, respectively. Also, 84% of players returned to football, all at the same or higher level than before surgery. At a mean follow-up of 9.8 years, all PROMs improved significantly from baseline (P < .002). Outcome scores at follow-up were as follows: mHHS 90.5; HOS-Activities of Daily Living, 94.5; HOS-Sports-Specific Subscale, 91.1; and visual analog scale (VAS) pain with use, 2.3/10; VAS pain at rest, 1.3/10; and surgical satisfaction, 8.5/10. No patients required revision surgery. However, 2 patients (7%) underwent reoperations—including 1 for heterotopic ossification excision and 1 for periacetabular osteotomy.Conclusion:American football players who underwent primary hip arthroscopy with labral repair for FAI achieved excellent long-term outcomes, with high RTS rates at the same or higher levels, and improvements in PROMs and patient satisfaction. Despite favorable outcomes, nonmedical factors, such as graduation, may influence RTS in competitive athletes, particularly at the high school and collegiate levels.