Effects of Soccer Heading on Brain Structure and Function

Neurocognitive Function Domains Are Not Affected in Active Professional Male Footballers, but Attention Deficits and Impairments Are Associated with Concussion

OBJECTIVE

To determine the neurocognitive function of active professional male footballers, determine whether deficits/impairments exist, and investigate the association between previous concussion(s) and neurocognitive function.

METHODS

An observational cross-sectional study conducted via electronic questionnaires. The CNS Vital Signs online testing system was used to evaluate neurocognitive function.

RESULTS

Of the 101 participants, 91 completed the neurocognitive function testing. Neurocognitive function domain deficits or impairments were unlikely in 54.5-89.1%, slight in 5.9-21.8%, moderate in 1.0-9.9%, and likely in 4.0-14.9% of participants. A history of zero concussions found a significant association between the neurocognitive index (Odds Ratio [OR] 0.6; 95% CI 0.2-0.4) and complex attention domain (OR 0.3; 95% CI 0.1-0.9), with 40% and 70% less odds, respectively, of deficit/impairment. Among the 54.5% who reported any number of concussions, there were increased odds of neurocognitive domain deficits/impairments for complex attention (CA) [3.4 times more] and simple attention (SA) [3.1 times more].

CONCLUSION

In the active professional male footballer, most neurocognitive functions do not have significant deficits/impairments. The odds of neurocognitive function deficit/impairment were significantly increased threefold for CA and SA in those who reported a history of any concussion(s).

Changes in the central nervous system in football players: an MRI study

BACKGROUND

Football (soccer) is the world's most popular team sport.

PURPOSE

To comprehensively examine the brain in football (soccer) players, with the use of magnetic resonance imaging (MRI) techniques.

MATERIAL AND METHODS

The study involved 65 football players and 62 controls. The MR examinations were performed using MR 1.5-T system (Optima MR 360; GE Medical Systems). The examinations were carried out in the 3D Bravo, CUBE, FSEpropeller, and diffusion-weighted imaging (DWI) sequences. The 1HMRS signal was obtained from the volume of interest in the frontal and occipital lobes on both sides.

RESULTS

The present study, based on structural MRI, shows some changes in the brains of the group of football players. The findings show asymmetry of the ventricular system in four football players, arachnoid cysts in the parieto-occipital region, and pineal cysts. NAA/Cr concentration in the right frontal lobe was lower in the football players than in the controls, and the Glx/Cr concentration in the right occipital lobe was higher. The apparent diffusion coefficient value is lower in football players in the occipital lobes.

CONCLUSION

Playing football can cause measurable changes in the brain, known to occur in patients diagnosed with traumatic brain injury. The present findings fill the gap in the literature by contributing evidence showing that playing football may lead to changes in the brain, without clinical symptoms of concussion.

The Acute Effects of Ball Pressure on Anticipation Timing Following a Series of Purposeful Headers in Adult Football (Soccer) Players

The purpose of this study is to investigate the acute effects of ball pressure on anticipation timing following a series of purposeful headers in adult football (soccer) players. There is evidence to suggest acute neurophysiological changes to the brain following purposeful heading; this may lead to altered anticipation timing as a result, potentially having future safety implications for players. A repeated measures crossover design was used. Seventeen participants aged between 20 and 30 years performed (i) 20 rotational headers with a lower-pressure match ball (58.6 kPa; 8.5 psi), (ii) 20 rotational headers with a higher-pressure match ball (103.4 kPa; 15 psi), or (iii) 20 non-headers (kicks) as a control each on separate days. The effect of ball pressure on anticipation timing accuracy, measured as absolute, constant, and variable errors, was assessed before and immediately after each intervention session using an anticipation timing task. Differences between group means were compared using repeated measures ANOVA and linear mixed effects models, with p-values of <0.05 considered statistically significant. No significant differences in anticipation timing accuracy across interventions were detected between control, occluded, and non-occluded trials. This finding differs from the previous literature regarding the measurable, acute effects of purposeful heading. The anticipation timing task may lack sensitivity for detecting the effects of repeated heading on brain function.

High magnitude exposure to repetitive head impacts alters female adolescent brain activity for lower extremity motor control

Contact and collision sport participation among adolescent athletes has raised concerns about the potential negative effects of cumulative repetitive head impacts (RHIs) on brain function. Impairments from RHIs and sports-related concussions (SRC) may propagate into lingering neuromuscular control. However, the neural mechanisms that link RHIs to altered motor control processes remain unknown. The purpose of this study was to isolate changes in neural activity for a lower extremity motor control task associated with the frequency and magnitude of RHI exposure. A cohort of fifteen high school female soccer players participated in a prospective longitudinal study and underwent pre- and post-season functional magnetic resonance imaging (fMRI). During fMRI, athletes completed simultaneous bilateral ankle, knee, and hip flexion/extension movements against resistance (bilateral leg press) to characterize neural activity associated with lower extremity motor control. RHI data were binned into continuous categories between 20 g - 120 g (defined by progressively greater intervals), with the number of impacts independently modeled within the fMRI analyses. Results revealed that differential exposure to high magnitude RHIs (≥90 g - < 110 g and ≥ 110 g) was associated with acute changes in neural activity for the bilateral leg press (broadly inclusive of motor, visual, and cognitive regions; all p < 0.05 & z > 3.1). Greater exposure to high magnitude RHIs may impair lower extremity motor control through maladaptive neural mechanisms. Future work is warranted to extend these mechanistic findings and examine the linkages between RHI exposure and neural activity as it relates to subsequent neuromuscular control deficits.

A prospective investigation of the effects of soccer heading on cognitive and sensorimotor performances in semi-professional female players

Introduction

Repetitive head impacts (RHI) from routine soccer (football) heading have been suggested to contribute to the long-term development of neurodegenerative disorders. However, scientific evidence concerning the actual risk of these RHI on brain health remains inconclusive. Moreover, female athletes-despite a presumably increased vulnerability toward the effects of RHI-are largely underrepresented in previous approaches. Therefore, our aim was to prospectively investigate the effects of heading on cognitive and sensorimotor performances, health perception, and concussion symptoms in semi-professional female soccer players.

Methods

An extensive test battery was used to assess cognitive and sensorimotor performances as well as health status (SF-36) and concussion symptoms (SCAT3) of a total of 27 female soccer players (22.2 ± 4.2 years) and 15 control subjects (23.2 ± 3.0 years) before and after one-and-a-half years. Throughout this period, soccer players' heading exposure was determined using video analysis.

Results

Subgroup comparisons (control [n = 12], low exposure [n = 7], high exposure [n = 8]) showed no time-dependent differences in SF-36 or SCAT3 scores. Similarly, across most behavioral tests, soccer players' performances evolved equally or more favorably as compared to the control subjects. However, there were significant effects pointing toward slightly negative consequences of heading on aspects of fine motor control (p = 0.001), which were confirmed by correlation and multiple regression analyses. The latter, further, yielded indications for a relationship between heading exposure and negative alterations in postural control (p = 0.002).

Discussion

Our findings do not provide evidence for negative effects of soccer heading on female players' health perception, concussion symptoms, and cognitive performances over the course of one-and-a-half years. However, we found subtle negative alterations in fine motor and postural control that could be attributed to heading exposure. Other factors, like the number of previous head injuries, were not linked to the observed changes. Given the reduction of our initial sample size due to player fluctuation, the results need to be interpreted with caution and validated in larger-scale studies. These should not only focus on cognitive outcomes but also consider sensorimotor changes as a result of RHI from soccer heading.

Decrease in aerial challenges after revision of goal kick rules in Japan Professional Soccer League: explorative study of the possibility of a risk reduction for head injury, concussion, and brain damage by a rule revision

In 2019, FIFA revised the goal kick (GLK) rule such that a GLK could be performed even if the kicker had teammates in the penalty area. This study aimed to examine whether the rule revision reduced the frequency of aerial challenge (AC) and long GLKs (LGLKs), which are risk factors for head injury and concussion in soccer. We analyzed all official league matches (306 matches/season) of the Japan Professional Soccer League 1st Division before (2018 season) and after the rule revision (2020 season). The analysis categorized GLKs into short GLKs (SGLKs) and LGLKs, depending on the GLK distance, and included the frequency and causes of AC, in each match following a GLK, which were compared between the 2018 and 2020 seasons. The average number of LGLKs per match in the 2020 season (8.85) decreased compared to that in the 2018 season (14.20). Additionally, for ACs following a GLK, the frequency of ACs decreased from 6.08 to 3.92 per match. Meanwhile, the frequency of LGLKs tended to increase toward the end of the first and second halves in matches. The results of this study revealed that the 2019 GLK rule revision reduced the number of LGLKs and ACs.

Individualized monitoring of longitudinal heading exposure in soccer

There is growing concern that repetitive soccer headers may have negative long-term consequences on brain health. However, inconsistent and low-quality heading exposure measurements limit past investigations of this effect. Here we conducted a comprehensive heading exposure analysis across all players on a university women's soccer team for over two calendar years (36 unique athletes), quantifying both game and practice exposure during all in-season and off-season periods, with over ten thousand video-confirmed headers. Despite an average of approximately 2 headers per day, players' daily exposures ranged from 0 to 45 headers, accumulating to highly variable total exposure of 2-223 headers over each in-season/off-season period. Overall, practices and off-season periods accounted for 70% and 45% of headers, respectively. Impact sensor data showed that heading kinematics fell within a tight distribution, but sensors could not capture full heading exposure due to factors such as compliance. With first-of-its-kind complete heading exposure data, we recommend exposure assessments be made on an individual level and include practice/off-season collection in addition to games and competitive seasons. Commonly used group statistics do not capture highly variable exposures, and individualized complete heading exposure tracking needs to be incorporated in future study designs for confirming the potential brain injury risk associated with soccer heading.

Heading and risk of injury situations for the head in professional German football: a video analysis of over 150,000 headers in 110,000 match minutes

To provide detailed epidemiological data on situations with a propensity of head injuries due to heading in professional football. In a prospective cohort study including the four highest professional football leagues in Germany, headers carried out in 1244 official matches and critical situations (CI) with a potential risk for injuries over one season were assessed by video analysis and a standardised video protocol. Results: 154,766 headers in 111,960 match minutes were recorded (1.4 headings/min). Video analysis showed a mean of 6.2 headers per field player and match (SD: 2,9; min: 0; max: 19) in the entire study population with a peak in the third league (7.1 per player and match). Headers were predominantly carried out with the forehead (78.5%), and nearly two-thirds occurred during defence (64.3%). 49.9% of all headers occurred during tackling, of which 78.3% involved body contact with an opponent. Video analysis yielded 848 CI. 74.5% of all critical incidents occurred during heading duels as a part of tackling (odds ratio: 3.6, 95%-CI: 2.4-5.2), and 99.4% involved body contact (odds ratio: 5.9, 95%-CI: 2,8-12,7). This study is the first to provide detailed epidemiological data on heading and critical incidences with high risk for head injuries in professional football. Heading duels bear a high risk of head injury and thus represent a key target for prevention strategies. The impacts of headers should be critically investigated regarding neurological consequences in further studies, by including the mean heading rate per mal field player and match.

Repetitive bout of controlled soccer heading does not alter heart rate variability metrics: A preliminary investigation

Objectives

There is elevated unease regarding how repetitive head impacts, such as those associated with soccer heading, contribute to alterations in brain function. This study examined the extent heart rate variability (HRV) and cardiac baroreceptor sensitivity (BRS) metrics are altered immediately following an acute bout of soccer heading.

Methods

Seven male elite soccer players (24.1 ± 1.5 years) completed 40 successful soccer headers in 20-min. The headers were performed under controlled circumstances using a soccer ball launcher located 25 meters away and using an initial ball velocity of 77.5 ± 3.7 km/h (heading condition). An accelerometer (xPatch) on the right mastoid process quantified linear/rotational head accelerations. Participants also completed sham (body contact) and control (non-contact) sessions. A three-lead ECG and finger photoplethysmography characterized short-term spontaneous HRV/cardiac BRS, before and after each condition. The SCAT3 indexed symptom scores pre-post exposures to all three conditions.

Results

During the heading condition, cumulative linear and rotational accelerations experienced were 1,574 ± 97.9 g and 313,761 ± 23,966 rad/s², respectively. Heart rate trended toward an increase from pre- to post-heading (p = 0.063), however HRV metrics in the time-domain (ps > 0.260) and frequency-domain (ps > 0.327) as well as cardiac BRS (ps > 0.144) were not significantly changed following all three conditions. Following the heading condition, SCAT3 symptom severity increased (p = 0.030) with a trend for symptom score augmentation (p = 0.078) compared to control and sham.

Conclusion

Whereas, symptoms as measured by the SCAT3 were induced following an acute bout of controlled soccer heading, these preliminary findings indicate they were not accompanied by alterations to autonomic function. Ultimately, this demonstrates further research is needed to understand the physiological underpinnings of alterations in brain function occurring immediately after a bout of soccer heading and how these may, over time, contribute to long-term neurological impairments.

A neural network for the detection of soccer headers from wearable sensor data

To investigate the proposed association between soccer heading and deleterious brain changes, an accurate quantification of heading exposure is crucial. While wearable sensors constitute a popular means for this task, available systems typically overestimate the number of headers by poorly discriminating true impacts from spurious recordings. This study investigated the utility of a neural network for automatically detecting soccer headers from kinematic time series data obtained by wearable sensors. During 26 matches, 27 female soccer players wore head impacts sensors to register on-field impact events (> 8 g), which were labelled as valid headers (VH) or non-headers (NH) upon video review. Of these ground truth data, subsets of 49% and 21% each were used to train and validate a Long Short-Term Memory (LSTM) neural network in order to classify sensor recordings as either VH or NH based on their characteristic linear acceleration features. When tested on a balanced dataset comprising 271 VHs and NHs (which corresponds to 30% and 1.4% of ground truth VHs and NHs, respectively), the network showed very good overall classification performance by reaching scores of more than 90% across all metrics. When testing was performed on an unbalanced dataset comprising 271 VHs and 5743 NHs (i.e., 30% of ground truth VHs and NHs, respectively), as typically obtained in real-life settings, the model still achieved over 90% sensitivity and specificity, but only 42% precision, which would result in an overestimation of soccer players' true heading exposure. Although classification performance suffered from the considerable class imbalance between actual headers and non-headers, this study demonstrates the general ability of a data-driven deep learning network to automatically classify soccer headers based on their linear acceleration profiles.

Automated soccer head impact exposure tracking using video and deep learning

Head impacts are highly prevalent in sports and there is a pressing need to investigate the potential link between head impact exposure and brain injury risk. Wearable impact sensors and manual video analysis have been utilized to collect impact exposure data. However, wearable sensors suffer from high deployment cost and limited accuracy, while manual video analysis is a long and resource-intensive task. Here we develop and apply DeepImpact, a computer vision algorithm to automatically detect soccer headers using soccer game videos. Our data-driven pipeline uses two deep learning networks including an object detection algorithm and temporal shift module to extract visual and temporal features of video segments and classify the segments as header or nonheader events. The networks were trained and validated using a large-scale professional-level soccer video dataset, with labeled ground truth header events. The algorithm achieved 95.3% sensitivity and 96.0% precision in cross-validation, and 92.9% sensitivity and 21.1% precision in an independent test that included videos of five professional soccer games. Video segments identified as headers in the test data set correspond to 3.5 min of total film time, which can be reviewed through additional manual video verification to eliminate false positives. DeepImpact streamlines the process of manual video analysis and can help to collect large-scale soccer head impact exposure datasets for brain injury research. The fully video-based solution is a low-cost alternative for head impact exposure monitoring and may also be expanded to other sports in future work.

Changes in circulating microRNAs following head impacts in soccer

AIM

To explore the short-term effects of accidental head impacts and repetitive headers on circulating microRNAs, accounting for the effects of high-intensity exercise alone.

METHODS

Blood samples were collected from professional soccer players at rest. Repeat samples were drawn 1 h and 12 h after three conditions: (1) accidental head impacts in a match, (2) repetitive headers during training, and (3) high-intensity exercise. 89 samples were screened to detect microRNAs expressed after each exposure. Identified microRNAs were then validated in 98 samples to determine consistently deregulated microRNAs. Deregulated microRNAs were further explored using bioinformatics to identify target genes and characterize their involvement in biological pathways.

RESULTS

Accidental head impacts led to deregulation of eight microRNAs that were unaffected by high-intensity exercise; target genes were linked to 12 specific signaling pathways, primarily regulating chromatin organization, Hedgehog and Wnt signaling. Repetitive headers led to deregulation of six microRNAs that were unaffected by high-intensity exercise; target genes were linked to one specific signaling pathway (TGF-β). High-intensity exercise led to deregulation of seven microRNAs; target genes were linked to 31 specific signaling pathways.

CONCLUSION

We identified microRNAs specific to accidental head impacts and repetitive headers in soccer, potentially being useful as brain injury biomarkers.

Purposeful Heading in Youth Soccer: A Review

Recent public concern over the short- and long-term effects of repetitive head impacts (RHI) associated with purposeful heading in soccer has led researchers to study a multitude of variables related to this important aspect of the game. Of particular interests are the effects of soccer heading in the youth population (≤ 13 years old) whose brains are undergoing rapid development. We conducted a review on youth soccer heading that includes purposeful heading frequency, head impact biomechanics, head injuries, clinical outcomes, and modifying factors. We have concluded that youth soccer players head the ball at a low frequency that typically increases with age and with a finding that boys head the ball more often than girls do. Interestingly, although girls head the ball less frequently than boys do, they tend to sustain higher head impact magnitudes. Head injuries are more likely to occur in girls versus boys and during games because of contact with another player. Clinical outcome measures of concussion are often utilized to study the effects of soccer heading, in both field and laboratory environments. Immediately following soccer heading, youth often report having a headache and demonstrate some deficits in balance measures. Modifying factors that may benefit soccer players participating in purposeful heading activities include stronger neck musculature, wearing headgear, and the use of mouthguards. Research involving youth soccer players needs to be expanded and funded appropriately to better understand the consequences of RHI in both the short and long term.

The 2015 U.S. Soccer Federation header ban and its effect on emergency room concussion rates in soccer players aged 10-13

BACKGROUND

In 2015, the U.S. Soccer Federation banned heading for players aged 10-13.

PURPOSE/QUESTION

To assess the change in proportion of children aged 10-13 playing soccer in the US presenting to an Emergency Department (ED) with a concussion in relation to any other injury before and after the ban.

METHODS

Analysis was restricted to soccer athletes between 10-13 years that reported to a National Electronic Injury Surveillance System (NEISS) participating hospital ED following injury in 2013-2014 and 2016-2017. Multivariable logistic regression was performed to assess the association between year of injury and concussion diagnosis in relation to other injury diagnosis after adjusting for age, sex, and ethnicity.

RESULTS

Concussion in relation to other injuries showed a significant increase in 2016-2017 when compared to 2013-2014 after adjustment (OR= 1.286, 95%CI = 1.090-1.517).

CONCLUSIONS

These results suggest that banning heading may not reduce concussion within this population. However, significant confounders, including increased reporting, were not controlled for.

Changes in resting-state functional brain connectivity associated with head impacts over one men's semi-professional soccer season

Soccer, as a contact sport, exposes players to repetitive head impacts, especially through heading the ball. The question of a long-term brain cumulative effect remains. Our objective was to determine whether exposure to head impacts over one soccer season was associated with changes in functional brain connectivity at rest, using magnetic resonance imaging (MRI). In this prospective cohort study, 10 semi-professional men soccer players, aged 18-25 years, and 20 age-matched men athletes without a concussion history and who do not practice any contact sport were recruited in Bordeaux (France). Exposure to head impacts per soccer player during competitive games over one season was measured using video analysis. Resting-state functional magnetic resonance imaging data were acquired for both groups at two times, before and after the season. With a seed-based analysis, resting-state networks that have been intimately associated with aspects of cognitive functioning were investigated. The results showed a mean head impacts of 42 (±33) per soccer player over the season, mainly intentional head-to-ball impacts and no concussion. No head impact was found among the other athletes. The number of head impacts between the two MRI acquisitions before and after the season was associated with increased connectivity within the default mode network and the cortico-cerebellar network. In conclusion, our findings suggest that the brain functioning changes over one soccer season in association with exposure to repetitive head impacts.

Heading in the Right Direction: A Critical Review of Studies Examining the Effects of Heading in Soccer Players

The practice of heading in soccer has become a public concern because of the potential for subconcussive impacts to cause cumulative concussive-like effects; however, experimental evidence for this hypothesis has been mixed. This systematic review used pre-defined search parameters to assess primary literature that examined changes in cognitive, behavioral, structural, and/or biological processes after acute heading exposure in youth and young adult soccer players. The findings were synthesized into a concise and comprehensive summary of the research following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) format, and suggestions for standardization of acute heading protocols are described. A total of 1189 articles were considered for this review, with 19 articles meeting all of the inclusion criteria for full analysis. An attempt was made to identify methods with significant sensitivity and reliability by grouping studies based on their outcome measures. Because of lack of standardization across intervention types and data collection protocols, no sensitive and reliable methods could be identified conclusively to assess the effects of acute heading exposure in soccer players. Based on this review, there is not enough evidence to either support or refute the potential of effects of subconcussive events from acute soccer heading exposure. Recommendations for standardization of acute heading exposure studies based on the included literature are discussed. Standardization is required to better understand the impact of acute heading exposure in soccer players, while allowing for the development of guidelines that mitigate any potential risks and allowing athletes to remain active and develop their skills.

Factors affecting peak impact force during soccer headers and implications for the mitigation of head injuries

It has been documented that up to 22% of all soccer injuries are concussions. This is in part due to players purposely using their head to direct the ball during play. To provide a more complete understanding of head trauma in soccer athletes, this study characterized the effects of four soccer ball characteristics (size, inflation pressure, mass, velocity) on the resulting peak impact force as it relates to the potential for incurring neurophysiological changes. A total of six hundred trials were performed on size 4 and 5 soccer balls as well as a novel lightweight soccer ball. Impact force was measured with a force plate and ball velocity was determined using motion capture. These data were used, in conjunction with dimensional analysis to relate impact force to ball size, mass, velocity, and pressure. Reasonable reductions in allowable ball parameters resulted in a 19.7% decrease in peak impact force. Adjustments to ball parameters could reduce a high cumulative peak translational acceleration soccer athlete down into a previously defined safer low loading range. In addition, it was noted that water absorption by soccer balls can result in masses that substantially increase impact force and quickly surpass the NCAA weight limit for game play. Additional research is required to determine whether varying soccer ball characteristics will enable soccer players to avoid persistent neurophysiological deficits or what additional interventions may be necessary and the legal implications of these data are discussed.

Soccer heading and concussion are not associated with reduced brain volume or cortical thickness

Soccer is the most popular sport in the world and, since it is a contact sport, players are at risk for head injury, including concussion. Here, we proposed to investigate the association of heading and concussion with macroscopic brain structure among adult amateur soccer players. For this study, 375 amateur soccer players (median age 23 years) completed HeadCount-12m to estimate heading over the 12 months prior to MRI and lifetime concussion. T1-weighted 3D magnetization prepared rapid acquisition gradient echo (MP-RAGE) MRI was performed at 3 Tesla. Parcellation was performed using Freesurfer to extract regional gray and white matter volumes as well as regional cortical thickness and total intracranial volume. Regional cortical brain volumes were normalized by total intracranial volume. We categorized heading into quartiles and concussion as 0, 1 or 2 or more. Generalized linear regressions were used to test the association of heading or concussion with each brain morphometry metric, including age and sex, as covariates. Neither heading nor concussion were associated with reduced brain volume or cortical thickness. We observed that greater heading was associated with greater gray matter volume in the left inferior parietal area, which may reflect effects related to training.

An Acute Bout of Soccer Heading Subtly Alters Neurovascular Coupling Metrics

Objective: The current investigation examined how a bout of soccer heading may impact brain function.

Design: Semi-randomized crossover cohort.

Setting: Controlled soccer heading.

Participants: Seven male soccer players (24.1 ± 1.5 years).

Intervention: 40 successful soccer headers were performed in 20 min (25 m, launch velocity ~80 km/h). X2 xPatch recorded linear and rotational head accelerations during each impact. A contact control “sham” condition – ball made body contact, but not by the head; and a no activity time “control” condition were also completed.

Main Outcome Measures: Posterior and middle cerebral artery (PCA and MCA, respectively), cerebral blood velocity (CBV) was recorded during a visual task (neurovascular coupling: NVC) alongside SCAT3 symptoms scores pre/post a controlled bout of soccer heading.

Results: Cumulative linear and rotational accelerations were 1,574 ± 97.9 g and 313,761 ± 23,966 rads/s², respectively, during heading and changes in SCAT3 symptom number (pre: 2.6 ± 3.0; post: 6.7 ± 6.2, p = 0.13) and severity (pre: 3.7 ± 3.6, post: 9.4 ± 7.6, p = 0.11) were unchanged. In the PCA, no NVC differences were observed, including: relative CBV increase (28.0 ± 7.6%, p = 0.71) and total activation (188.7 ± 68.1 cm, p = 0.93). However, MCA-derived NVC metrics were blunted following heading, demonstrating decreased relative CBV increase (7.8 ± 3.1%, p = 0.03) and decreased total activation (26.7 ± 45.3 cm, p = 0.04).

Conclusion: Although an acute bout of soccer heading did not result in an increase of concussion-like symptoms, there were alterations in NVC responses within the MCA during a visual task. This suggests an acute bout of repetitive soccer heading can alter CBV regulation within the region of the brain associated with the header impacts.

Soccer heading and subclinical neuropsychiatric symptomatology in professional soccer players

Objectives

To evaluate the association between postconcussive symptomatology and heading in professional soccer players, overcoming the bias of self-reported exposure, we evaluated several clinical neuropsychiatric symptoms using questionnaires after a thorough objective follow-up of players’ heading exposure throughout an entire season.

Methods

We collected heading data for all Israeli Premier League players for an entire season using a web-based platform for performance analysis, which enabled us to quantify the exact number of headers per player. Players filled out questionnaires regarding postconcussion symptoms, depression, anxiety, and sleep disorders. We tested the association between the number of headers and each outcome using a negative binomial regression corrected for the hours played.

Results

A total of 159 players were included, of whom 79 were considered in the high heading exposure group (49%), defined as more than median number of headings (1.34 per game hour). Among players without any past head injury, those with higher heading exposure were less likely to have postconcussion symptoms compared with players with low heading exposure (relative risk [RR] per heading per hour 0.94, 95% confidence interval [CI] 0.912–0.963). Players with high heading exposure had fewer depression symptoms (RR 0.98, 95% CI 0.961–0.997), anxiety (RR 0.98, 95% CI 0.958–0.997), and sleep disorders (RR 0.98, 95% CI 0.961–0.996).

Conclusion

Professional soccer players with high heading rate do not display higher postconcussive symptomatology severity. Symptoms among players with low heading exposure might be explained by low resilience, possibly associated with an inferior heading technique. Alternatively, it can reflect heading-avoidant behavior.

Concussion in soccer: a comprehensive review of the literature

Sports-related concussion has been examined extensively in collision sports such as football and hockey. However, historically, lower-risk contact sports such as soccer have only more recently garnered increased attention. Here, we review articles examining the epidemiology, injury mechanisms, sex differences, as well as the neurochemical, neurostructural and neurocognitive changes associated with soccer-related concussion. From 436 titles and abstracts, 121 full texts were reviewed with a total of 64 articles identified for inclusion. Concussion rates are higher during competitions and in female athletes with purposeful heading rarely resulting in concussion. Given a lack of high-level studies examining sports-related concussion in soccer, clinicians and scientists must focus research efforts on large-scale data gathering and development of improved technologies to better detect and understand concussion.

Repeated Long-Term Sub-concussion Impacts Induce Motor Dysfunction in Rats: A Potential Rodent Model

Whilst detrimental effects of repeated sub-concussive impacts on neurophysiological and behavioral function are increasingly reported, the underlying mechanisms are largely unknown. Here, we report that repeated sub-concussion with a light weight drop (25 g) in wild-type PVG rats for 2 weeks does not induce detectable neuromotor dysfunction assessed by beamwalk and rotarod tests. However, after 12 weeks of repeated sub-concussion, the rats exhibited moderate neuromotor dysfunction. This is the first study to demonstrate development of neuromotor dysfunction following multiple long-term sub-concussive impacts in rats. The outcomes may offer significant opportunity for future studies to understand the mechanisms of sub-concussion-induced neuropsychological changes.

The UEFA Heading Study: Heading incidence in children's and youth' football (soccer) in eight European countries

To assess the real-life magnitude of the heading incidence in children's and youth' football in eight European countries with different "football cultures," a cross-sectional observational design, in which one match per team in 480 different teams from eight European countries (2017/18-2018/19), was recorded by video. One training session was recorded in 312 teams. Clubs with Under-10, Under-12 (female/male/mixed), and Under-16 female and male teams were eligible to participate. Heading frequencies and types were analyzed. Results are presented as headers per match/training and per team. Incidence rates (IR) per 1000 match/training hours were calculated. Under-10 teams carried out the lowest average number of headers per match (8.8), followed by Under-16 female (17.7), Under-12 (18.4), and Under-16 male (35.5). Total number of headers per match and team varied between countries. 80% of the total number of headers were single intentional headers, 12% heading duels, 3% unintentional headers by getting hit, and 5% others (trends apparent in all age groups). Three head injuries occurred during match play corresponding to an IR of 0.70 (95% CI, 0.23-2.16). The lowest number of headers per training and team was found in Under-10 (21.3), followed by Under-16 females (34.1), Under-12 (35.8), and Under-16 males (45.0). In conclusion, this large-scale study presents novel data about the number and type of headers in youth' football throughout Europe. A more precise understanding of the heading incidence, specifically in young players, is mandatory for the debate of restrictions on heading in youth football.

A pilot study of diffusion tensor imaging metrics and cognitive performance pre and post repetitive, intentional sub-concussive heading in soccer practice

Background

Although soccer players routinely head the ball in practice and games, recent research has suggested that cumulative effects of repetitive heading may cause sub-concussive injury with accompanying effects on brain and behavior. The current study aimed to prospectively investigate the effects of repetitive, intentional heading in soccer practice on brain structure and cognitive function, using a within-subjects design.

Methods

Participants included 10 soccer players (mean age 20.09 years ± 2.88) who were examined immediately pre- and post-heading practice. An accelerometer was used to measure the force of the impact during soccer heading. Magnetic resonance imaging data were acquired on a 3 T GE Scanner with diffusion tensor imaging. Diffusion tensor imaging analyses were completed using functional magnetic resonance imaging of the brain software library’s Tract-Based Spatial Statistics to examine changes in both fractional anisotropy and mean diffusivity due to heading the soccer ball. Behavioral measures were also completed pre- and post-soccer heading and included the Sport Concussion Assessment Tool and three short-computerized executive function tasks; R studio was used to compare behavioral data within subjects.

Results

Accelerometer data revealed that none of the heading impacts were >10 g. At this level of impact, there were no significant pre–post heading differences in either fractional anisotropy or mean diffusivity. Additionally, aside from minimal practice effects, there were no significant differences in Sport Concussion Assessment Tool scores and no significant differences in the performance of the three executive function tasks pre–post heading.

Conclusions

The results provide initial evidence that repetitive heading in soccer practice, at a g force of 10, does not cause changes in brain structure or executive function. Future research should investigate heading in the context of games and with a greater sample size that would allow for sex-based comparisons.

No Evidence of Association Between Soccer Heading and Cognitive Performance in Professional Soccer Players: Cross-Sectional Results

Although the scientific community has focused on the effects of concussions in contact sports, the role of subconcussive impacts, as it can occur during soccer heading, has recently gained attention, considering that it may represent an additional mechanism of cumulative brain injury. The aim of this study is to investigate the effects of soccer heading on cognitive functioning in active professional soccer players. Male soccer players (n = 44), from two soccer teams that play in the Brazilian A Series Championship, and non-athletes (n = 47), comparable in age and education, were submitted to cognitive assessment, consisting of computerized and conventional neuropsychological testing (Neupsilin battery). In the computerized cognitive assessment, soccer players performed better than controls on reaction time measures in general motor coordination, executive functioning and memory tests, and on accuracy measures in executive functioning tests. There were no significant differences between groups on the Neupsilin battery. A comparison between two sub-groups of soccer players, based on the self-reported number of headings, did not show significant differences on tests performance. No significant correlations were found between an estimate of exposure to heading during professional soccer career and cognitive performance. Our data demonstrate no evidence of cognitive impairment in soccer players, compared to non-athletes, and no association between heading exposure and performance on neuropsychological tests. Longitudinal investigations, including neuroimaging assessment, will help to clarify whether soccer heading may be associated with brain injury and cognitive dysfunction.

The neurobiological effects of repetitive head impacts in collision sports

It is now recognized that repetitive head impacts (RHI) in sport have the potential for long-term neurological impairments. In order to identify targets for intervention and/or pharmacological treatment, it is necessary to characterize the neurobiological mechanisms associated with RHI. This review aims to summarize animal and human studies that specifically address Blood Brain Barrier (BBB) dysfunction, abnormal neuro-metabolic and neuro-inflammatory processes as well as Tau aggregation associated with RHI in collision sports. Additionally, we examine the influence of physical activity and genetics on outcomes of RHI, discuss methodological considerations, and provide suggestions for future directions of this burgeoning area of research.

Heading Frequency Is More Strongly Related to Cognitive Performance Than Unintentional Head Impacts in Amateur Soccer Players

Objective

Compared to heading, unintentional head impacts (e.g., elbow to head, head to head, head to goalpost) in soccer are more strongly related to risk of moderate to very severe Central Nervous System (CNS) symptoms. But, most head impacts associated with CNS symptoms that occur in soccer are mild and are more strongly related to heading. We tested for a differential relation of heading and unintentional head impacts with neuropsychological (NP) test performance.

Method

Active adult amateur soccer players were recruited in New York City and the surrounding areas for this repeated measures longitudinal study of individuals who were enrolled if they had 5+ years of soccer play and were active playing soccer 6+ months/year. All participants completed a baseline validated questionnaire (“HeadCount-2w”), reporting 2-week recall of soccer activity, heading and unintentional head impacts. In addition, participants also completed NP tests of verbal learning, verbal memory, psychomotor speed, attention, and working memory. Most participants also completed one or more identical follow-up protocols (i.e., HeadCount-2w and NP tests) at 3- to 6-month intervals over a 2-year period. Repeated measures General Estimating Equations (GEE) linear models were used to determine if variation in NP tests at each visit was related to variation in either heading or unintentional head impacts in the 2-week period before testing.

Results

308 players (78% male) completed 741 HeadCount-2w. Mean (median) heading/2-weeks was 50 (17) for men and 26 (7) for women. Heading was significantly associated with poorer performance on psychomotor speed (p < 0.001) and attention (p = 0.02) tasks and was borderline significant with poorer performance on the working memory (p = 0.06) task. Unintentional head impacts were not significantly associated with any NP test. Results did not differ after excluding 22 HeadCount-2w with reported concussive or borderline concussive symptoms.

Conclusion

Poorer NP test performance was consistently related to frequent heading during soccer practice and competition in the 2 weeks before testing. In contrast, unintentional head impacts incurred during soccer were not related to cognitive performance.

Sub-concussive trauma, acute concussion, and history of multiple concussions: Effects on quiet stance postural control stability

Although balance control has been studied extensively following acute concussion, little is known regarding repetitive sub-concussive head impacts or chronic exposure to multiple concussive events. Quiet stance postural control was characterized in contact sport athletes at pre-season (n = 135) and post-season (n = 48) to evaluate the effects of subconcussive trauma to the head. To determine the impact of acute concussion on postural control, athletes diagnosed with a concussion during the season (n = 12) were tested at 72-h, 2-weeks, and 1-month post-injury. Because only 4 of the concussed athletes completed baseline testing, control athletes (n = 12) matched for sport, age, body mass index (BMI), and previous concussion history served as a comparison group. Finally, the effects of previous concussion history on quiet stance postural control were determined by comparing pre-season data in contact sport athletes with either zero (Hx⁰, n = 50) or three or more (Hx³⁺, n = 25) previous concussions. A force plate was used to compare changes in centre-of-pressure root-mean-square displacement (RMSdisp) and mean-velocity (COPvel) in the anterior/posterior (AP) and medial/lateral (ML) directions. One-minute trials were performed with feet hip-width apart, hands-on-hips, and A) eyes-open and B) eyes-closed. Biomechanical head-impact exposure (impacts over 10 g) was indexed over the season using mastoid-fixed impact sensors. In acutely injured athletes, repeated-measures ANOVA revealed a significant effect of time for RMSdisp AP with increased displacement at 2 weeks compared to 72 h (p = 0.008, 95% CI: -0.180, -0.310 cm). No other COP variables were affected by acute concussion. Moreover, there was no effect of concussion history or repeated sub-concussive impacts on any quiet stance metric. Additionally, head-impact exposure metrics were not correlated with COP metrics. Taken together, the data suggests alterations in COP sway during quiet stance persist in the acute 2-week period after injury. These findings were not present with either a history of multiple concussions or exposure to sub-concussive head impacts indicating acute concussion does not have appear to have long term effects for these measures.

Recent and Long-Term Soccer Heading Exposure Is Differentially Associated With Neuropsychological Function in Amateur Players

OBJECTIVES

The present study examined the relative contribution of recent or long-term heading to neuropsychological function in amateur adult soccer players.

PARTICIPANTS AND METHODS

Soccer players completed a baseline questionnaire (HeadCount-12m) to ascertain heading during the prior 12 months (long-term heading, LTH) and an online questionnaire (HeadCount-2w) every 3 months to ascertain heading during the prior 2 weeks (recent heading, RH). Cogstate, a battery of six neuropsychological tests, was administered to assess neuropsychological function. Generalized estimating equations were used to test if LTH or RH was associated with neuropsychological function while accounting for the role of recognized concussion.

RESULTS

A total of 311 soccer players completed 630 HeadCount-2w. Participants had an average age of 26 years. Participants headed the ball a median of 611 times/year (mean=1,384.03) and 9.50 times/2 weeks (mean=34.17). High levels of RH were significantly associated with reduced performance on a task of psychomotor speed (p=.02), while high levels of LTH were significantly associated with poorer performance on tasks of verbal learning (p=.03) and verbal memory (p=.04). Significantly better attention (p=.02) was detectable at moderately high levels of RH, but not at the highest level of RH. One hundred and seven (34.4%) participants reported a lifetime history of concussion, but this was not related to neuropsychological function and did not modify the association of RH or LTH with neuropsychological function.

CONCLUSION

High levels of both RH and LTH were associated with poorer neuropsychological function, but on different domains. The clinical manifestations following repetitive exposure to heading could change with chronicity of exposure. (JINS, 2018, 24, 147-155).

Soccer (Football Association) and chronic traumatic encephalopathy: A short review and recommendation

Chronic traumatic encephalopathy (CTE) was initially described in boxers, but in recent years it has been reported in other settings, particularly in contact sports and military personnel. Soccer (football association) had previously been (and still is) considered relatively safe when compared to other sports, such as American football. However, a few cases of professional soccer players with CTE have been reported in the last few years. It is still unknown how frequent this condition is in soccer players, and the role played by heading the ball remains elusive. Other traumas to the head, face and neck caused by contact with another player's head, arm or other body parts are among the most frequent in soccer. In spite of the lack of more in-depth knowledge, there is reasonable evidence for recommending severe punishment (red card and suspension for several matches) for players causing avoidable trauma to another player's head.

White matter alterations over the course of two consecutive high-school football seasons and the effect of a jugular compression collar: A preliminary longitudinal diffusion tensor imaging study

The cumulative effects of repetitive subclinical head impacts during sports may result in chronic white matter (WM) changes and possibly, neurodegenerative sequelae. In this pilot study, we investigated the longitudinal WM changes over the course of two consecutive high-school football seasons and explored the long-term effects of a jugular vein compression collar on these WM alterations. Diffusion tensor imaging data were prospectively collected both pre- and postseason in the two consecutive seasons. Participants were assigned into either collar or noncollar groups. Tract-based spatial statistics (TBSS) approach and region of interest-based approach were used to quantify changes in WM diffusion properties. Despite comparable exposure to repetitive head impacts, significant reductions in mean, axial, and/or radial diffusivity were identified in Season 1 in multiple WM regions in the noncollar group but not in the collar group. After an 8- to 9-month long off-season, these changes observed in the noncollar group partially and significantly reversed but also remained significantly different from the baseline. In Season 2, trend level WM alterations in the noncollar group were found but located in spatially different regions than Season 1. Last, the WM integrity in the collar group remained unchanged throughout the four time points. In conclusion, we quantitatively assessed the WM structural changes and partial reversal over the course of two consecutive high-school football seasons. In addition, the mitigated WM alterations in athletes in the collar group might indicate potential effect of the collar in ameliorating the changes against repetitive head impacts. Hum Brain Mapp 39:491-508, 2018. © 2017 Wiley Periodicals, Inc.

Validation of HeadCount-2w for estimation of two-week heading: Comparison to daily reporting in adult amateur player

OBJECTIVES

To validate the HeadCount-2w questionnaire for estimation of 2-week soccer heading by comparison to daily electronic diary reporting over the same two-week period.

DESIGN

Prospective observational study.

METHODS

Adult amateur soccer players completed HeadCount-daily, comprising 14 daily at-home assessments of soccer play and heading via a tablet PC. Following the 14day period, players completed HeadCount-2w, a web-based two-week-recall questionnaire on soccer and heading. intraclass correlation coefficient (ICC) was estimated between HeadCount-daily, the reference standard, and HeadCount-2w estimates of heading during the same 2-week period.

RESULTS

53 participants (38 men) reported a mean of 24.36 (median=11.76) headers during 2 weeks via HeadCount-daily and a mean of 38.34 (median=15.0) headers for the same 2 weeks via HeadCount-2w. The ICC comparing 2-week heading from HeadCount-daily and HeadCount-2w was 0.85. Linear regression of the log-transformed Headcount-daily on HeadCount-2w data yielded a slope of 0.71 (p<0.001; 95% CI 0.54-0.82), suggesting that heading tends to be over-estimated by HeadCount-2w relative to HeadCount-daily. Slope estimates for men (0.65) and women (0.71) were similar.

CONCLUSIONS

HeadCount, a self-administered web-based survey, is valid for self-reporting 2-week heading in adult amateur players, supporting its use in future research and as a simple and low-cost technique for exposure monitoring.

Investigating Cognitive Performance Deficits in Male and Female Soccer Players after a 4-week Heading- Training Programme: A Controlled Study

This experimental study with a controlled pre-test and post-test group design investigated the possible effects of four sessions of heading training on cognitive performance. A total of 118 participants (mean age of 22.25 years) were assigned to one of the three following groups: a heading-training group, a passing-training group and a waiting control group. The participants completed a cognitive test battery of attention (D2-test), working memory (Paced Auditory Serial Addition Task, PASAT-2) and visual spatial intelligence (Mental Rotation Test) tests before, immediately after the second training session and one week after the fourth training session. There were no between-group differences in cognitive performance after the second or the fourth heading training sessions. However, within the heading-training group, women complained more of headaches than men after the fourth training session. These results build on the results from the study of Rieder and Jansen (2011) that showed no neuropsychological consequences after one heading session, showing no cumulative effects of repeat heading.

Symptoms from repeated intentional and unintentional head impact in soccer players

OBJECTIVE

To determine the rate and differential contribution of heading vs unintentional head impacts (e.g., head to head, goal post) to CNS symptoms in adult amateur soccer players.

METHODS

Amateur soccer players completed baseline and serial on-line 2-week recall questionnaires (HeadCount) and reported (1) soccer practice and games, (2) heading and unintentional soccer head trauma, and (3) frequency and severity (mild to very severe) of CNS symptoms. For analysis, CNS symptoms were affirmed if one or more moderate, severe, or very severe episodes were reported in a 2-week period. Repeated measures logistic regression was used to assess if 2-week heading exposure (i.e., 4 quartiles) or unintentional head impacts (i.e., 0, 1, 2+) were associated with CNS symptoms.

RESULTS

A total of 222 soccer players (79% male) completed 470 HeadCount questionnaires. Mean (median) heading/2 weeks was 44 (18) for men and 27 (9.5) for women. One or more unintentional head impacts were reported by 37% of men and 43% of women. Heading-related symptoms were reported in 20% (93 out of 470) of the HeadCounts. Heading in the highest quartile was significantly associated with CNS symptoms (odds ratio [OR] 3.17, 95% confidence interval [CI] 1.57-6.37) when controlling for unintentional exposure. Those with 2+ unintentional exposures were at increased risk for CNS symptoms (OR 6.09, 95% CI 3.33-11.17) as were those with a single exposure (OR 2.98, 95% CI 1.69-5.26) when controlling for heading.

CONCLUSIONS

Intentional (i.e., heading) and unintentional head impacts are each independently associated with moderate to very severe CNS symptoms.

Change of Muscle Activity as Well as Kinematic and Kinetic Parameters during Headers after Core Muscle Fatigue

In soccer, headers are a tactical measure and influenced by numerous factors. The goal of this study was to identify whether changes in kinematics and muscular activity, especially of the head-stabilizing muscles, occur during headers when the core musculature is fatigued. In two subgroups, muscular activity (12 amateur players, age 23.6 ± 4.2 years) and kinematics and dynamics (29 amateur players, age 23.7 ± 2.8 years) were examined during straight headers on a pendulum header. Data were collected before and after the core muscles were fatigued by an exercise program. Telemetric surface EMG, 3D acceleration sensor, force plate, and video recordings were used. Under fatigue, the activity of M. erector spinae and M. rectus abdominis was significantly reduced in the preparation phase of the header. The activity of M. sternocleidomastoideus was significantly increased during the jump phase, and the hip extension angle during maximum arched body tension was significantly reduced under fatigue. Jumping height, acceleration force impulse, and linear head acceleration were also significantly reduced. We conclude that fatigue of the core muscles affects the motion technique of the header and the activity of the muscle groups stabilizing the head. Therefore, the necessity of specific training in soccer should be emphasized from a medical-preventive point of view.

Validation and calibration of HeadCount, a self-report measure for quantifying heading exposure in soccer players

The long-term effects of repetitive head impacts due to heading are an area of increasing concern, and exposure must be accurately measured; however, the validity of self-report of cumulative soccer heading is not known. In order to validate HeadCount, a 2-week recall questionnaire, the number of player-reported headers was compared to the number of headers observed by trained raters for a men's and a women's collegiate soccer teams during an entire season of competitive play using Spearman's correlations and intraclass correlation coefficients (ICCs), and calibrated using a generalized estimating equation. The average Spearman's rho was 0.85 for men and 0.79 for women. The average ICC was 0.75 in men and 0.38 in women. The calibration analysis demonstrated that men tend to report heading accurately while women tend to overestimate. HeadCount is a valid instrument for tracking heading behaviour, but may have to be calibrated in women.