Accelerometers for the Assessment of Concussion in Male Athletes: A Systematic Review and Meta-Analysis

Unlocking the Impact: A Systematic Review and Meta-Analysis of Biomechanical Insights into Rugby Head Impacts Using Wearable Sensor Technology

BACKGROUND

In the realm of sports medicine, understanding the biomechanics of head impacts, particularly in contact sports such as rugby, is of utmost interest for injury prevention and player safety.

OBJECTIVE

This systematic review and meta-analysis aims to consolidate existing knowledge on head impacts in rugby using wearable sensor technology, focusing on peak linear acceleration, peak rotational acceleration, and impact location.

METHODS

A systematic search of electronic databases [PubMed, Web of Science (WOS), Scopus, Embase, SPORTDiscus, PsycINFO, and CINAHL] was conducted in March 2024, including studies that assessed head impacts with wearable technology in rugby athletes. The search did not impose any restrictions on publication dates and included studies published in English and Spanish. A random-effects meta-analysis model was employed to combine comparable data from the included studies.

RESULTS

The literature search yielded 13 prospective cohort studies, collectively analyzing 895 participants and 44,036 head impacts. Most studies were conducted in Australasia and North America, with varying levels of play represented, from junior to semi/professional and from both rugby codes, rugby union (RU) and rugby league (RL). Wearable sensors, including instrumented mouthguards and skin patches, were utilized to measure head impact kinematics, with peak linear acceleration consistently reported across all studies. Results reveal significant heterogeneity in peak linear and rotational acceleration, highlighting the complexity of quantifying impact magnitudes in rugby. Impact location analysis indicated side impacts as most prevalent (44%), followed by frontal (29%) and back impacts (19%). Notably, concussive events yielded a pooled peak linear acceleration estimate of 63.01 g, with the RL cohort exhibiting higher acceleration than RU.

CONCLUSION

This study contributes to the growing body of literature on head impacts in rugby; identifying available evidence on the magnitude and location of head impacts measured by sensors, and emphasizing the importance of wearable sensor technology in advancing player safety and informing injury management practices. Despite the valuable insights provided, limitations, including methodological inconsistencies and study heterogeneity, underscore the need for cautious interpretation. Further research is warranted to standardize protocols and enhance the understanding of effective injury prevention strategies in rugby. PROSPERO registration number: CRD42023480779 (20 November 2023).

Advancing Sports Cardiology: Integrating Artificial Intelligence with Wearable Devices for Cardiovascular Health Management

Sports cardiology focuses on athletes' cardiovascular health, yet sudden cardiac death remains a significant concern despite preventative measures. Prolonged physical activity leads to notable cardiovascular adaptations, known as the athlete's heart, which can resemble certain pathological conditions, complicating accurate diagnoses and potentially leading to serious consequences such as unnecessary exclusion from sports or missed treatment opportunities. Wearable devices, including smartwatches and smart glasses, have become prevalent for monitoring health metrics, offering potential clinical applications for sports cardiologists. These gadgets are capable of spotting exercise-induced arrhythmias, uncovering hidden heart problems, and offering crucial information for training and recovery, to minimize exercise-related cardiac incidents and enhance heart health care. However, concerns about data accuracy and the actionable value of the obtained information persist. A major challenge lies in the integration of artificial intelligence with wearables, research gaps remain regarding their ability to provide real-time, reliable, and clinically relevant insights. Combining artificial intelligence with wearable devices can improve how data is managed and used in sports cardiology. Artificial intelligence, particularly machine learning, can classify, predict, and draw inferences from the data collected by wearables, revolutionizing patient data usage. Despite artificial intelligence's proven effectiveness in managing chronic conditions, the limited research on its application in sports cardiology, particularly regarding wearables, creates a critical gap that needs to be addressed. This review examines commercially available wearables and their applications in sports cardiology, exploring how artificial intelligence can be integrated into wearable technology to advance the field.

Performance of current tools used for on-the-day assessment and diagnosis of mild traumatic brain injury in sport: a systematic review

Objective

The monitoring and diagnosis of sports-related mild traumatic brain injury (SR-mTBI) remains a challenge. This systematic review summarises the current monitoring tools used for on-the-day assessment and diagnosis of SR-mTBI and their performance.

Design

Systematic review, using Quality Assessment of Diagnostic Accuracy Studies assessment.

Data sources

Embase via Ovid, IEEEXplore, Medline via Ovid, Scopus and Web of Science were searched up to June 2024.

Eligibility criteria

Peer-reviewed English-language journal articles which measured athletes using the index test within a day of injury and provided a performance measure for the method used. Studies of all designs were accepted, and no reference methods were required.

Results

2534 unique records were retrieved, with 52 reports included in the review. Participants were 76% male, when reported, and the mean injury-to-measurement time was reported in 10% of reports. 46 different methods were investigated. 38 different reference methods were used, highlighting the lack of gold standard within the field. Area under the curve (AUC), sensitivity and specificity were the most frequent outcome metrics provided. The most frequent index test was the King-Devick (KD) test. However, there were large variations in accuracy metrics between reports for the KD test, for instance, the range of AUC: 0.51-0.92.

Conclusion

Combinations of existing methods and the KD test were most accurate in assessing SR-mTBI, despite the inconsistent accuracy values related to the KD test. The absence of a gold-standard measurement hampers our ability to diagnose or monitor SR-mTBI. Further exploration of the mechanisms and time-dependent pathophysiology of SR-mTBI could result in more targeted diagnostic and monitoring techniques. The Podium Institute for Sports Medicine and Technology funded this work.

PROSPERO registration number

CRD42022376560.

The Fundamentals and Applications of Wearable Sensor Devices in Sports Medicine: A Scoping Review

PURPOSE

To (1) characterize the various forms of wearable sensor devices (WSDs) and (2) review the peer-reviewed literature of applied wearable technology within sports medicine.

METHODS

A systematic search of PubMed and EMBASE databases, from inception through 2023, was conducted to identify eligible studies using WSDs within sports medicine. Data extraction was performed of study demographics and sensor specifications. Included studies were categorized by application: athletic training, rehabilitation, and research.

RESULTS

In total, 43 studies met criteria for inclusion in this review. Forms of WSDs include pedometers, accelerometers, encoders (consisting of magnetometers and gyroscopes), force sensors, global positioning system trackers, and inertial measurement units. Outcome metrics include step counts; gait, limb motion, and angular positioning; foot and skin pressure; change of direction and inclination, including analysis of both body parts and athletes on a field; displacement and velocity of body segments and joints; heart rate; plethysmography; sport-specific kinematics; range of motion, symmetry, and alignment; head impact; sleep; throwing biomechanics; and kinetic and spatiotemporal running metrics. WSDs are used in athletic training to assess sport-specific biomechanics and workload with a goal of injury prevention and training optimization, as well as for rehabilitation monitoring and research such as for risk predicting and aiding diagnosis.

CONCLUSIONS

WSDs enable real-time monitoring of human performance across a variety of implementations and settings, allowing collection of metrics otherwise not achievable. WSDs are powerful tools with multiple applications within athletic training, patient rehabilitation, and orthopaedic and sports medicine research.

CLINICAL RELEVANCE

Wearable technology may represent the missing link to quantitatively addressing return to play and previous performance. WSDs are commercially available and portable adjuncts that allow clinicians, trainers, and individual athletes to monitor biomechanical parameters, workload, and recovery status to better contextualize personalized training, injury risk, and rehabilitation.

Concussion biomechanics, head acceleration exposure and brain injury criteria in sport: a review

There are mounting concerns surrounding the risk of neurodegenerative diseases and complications associated with concussion incidence and repetitive head acceleration events (HAE) in sport. The aim of this review is to provide an overview of concussion biomechanics, head acceleration exposure and brain injury criteria in sport. Rotational head motion appears to be the primary contributor to brain injury risk due to the unique mechanical properties of the brain and its location within the body. There is a growing evidence base of different biomechanical brain injury mechanisms, including those involving repetitive HAE. Historically, many studies on concussion biomechanics, head acceleration exposure and brain injury criteria in sport have been limited by validity of the biomechanical approaches undertaken. Biomechanical approaches such as instrumented mouthguards and subject-specific finite element (FE) brain models provide a unique opportunity to develop greater brain injury criteria and aid in on-field athlete removal. Implementing these approaches on a large-scale can gain insight into potential risk factors within sports and certain athletes/cohorts who sustain a greater number and/or severity of HAE throughout their playing career. These findings could play a key role in the development of concussion prevention strategies and techniques that mitigate the severity of HAE in sport.

Characterizing Head Acceleration Events in Law Enforcement Cadets During Subject Control Technique Training

Law enforcement cadets (LECs) complete weeks of subject control technique training. Similar sport-related combat training has been shown to expose participants to head acceleration events (HAEs) that have potential to result in short- and long-term impairments. The purpose of this study was to describe the number and magnitude of HAEs in LECs throughout their training. 37 LECs (7 females; age = 30.6 ± 8.8 years; BMI = 30.0 ± 6.0) were recruited from a law enforcement organization. Participants wore instrumented mouthguards, which recorded all HAEs exceeding a resultant 5 g threshold for training sessions with the potential for HAEs. Participants completed three defensive tactics (DT) training sessions, a DT skill assessment (DTA), and three boxing sessions. Outcome measures included the number of HAEs, peak linear acceleration (PLA), and peak rotational velocity (PRV). There were 2758 true-positive HAEs recorded across the duration of the study. Boxing sessions accounted for 63.7% of all true-positive HAEs, while DT accounted for 31.4% and DTA accounted for 4.9%. Boxing sessions resulted in a higher number of HAEs per session (F2,28 = 48.588, p < 0.001, ηp2 = 0.776), and higher median PLA (F2,28 = 8.609, p = 0.001, ηp2 = 0.381) and median PRV (F2,28 = 11.297, p < 0.001, ηp2 = 0.447) than DT and DTA. The LECs experience a high number of HAEs, particularly during boxing sessions. Although this training is necessary for job duties, HAE monitoring may lead to modifications in training structure to improve participant safety and enhance recovery.

Repetitive Subconcussive Head Impacts in Sports and Their Impact on Brain Anatomy and Function: A Systematic Review

Repetitive subconcussive head impacts occur regularly in sports. However, the exact relationship between their biomechanical properties and their consequences on brain structure and function has not been clarified yet. We therefore reviewed prospective cohort studies that objectively reported the biomechanical characteristics of repetitive subconcussive head impacts and their impact on brain anatomy and function. Only studies with a pre- to post-measurement design were included. Twenty-four studies met the inclusion criteria. Structural white matter alterations, such as reduced fractional anisotropy and an increase in mean diffusivity values, seem to be evident in athletes exposed to repetitive subconcussive head impacts exceeding 10 g. Such changes are observable after only one season of play. Furthermore, a dose-response relationship exists between white matter abnormalities and the total number of subconcussive head impacts. However, functional changes after repetitive subconcussive head impacts remain inconclusive. We therefore conclude that repetitive subconcussive head impacts induce structural changes, but thus far without overt functional changes.

The interaction of digital economy, artificial intelligence and sports industry development --based on China PVAR analysis of provincial panel data

Under the leadership of China's "dual-carbon" goal, clarifying the interaction between the digital economy, artificial intelligence, and the sports industry is an important guarantee to promote the structural upgrading of China's sports industry and achieve low-carbon development. Therefore, a panel vector autoregression (PVAR) model is constructed based on the panel data of 15 provinces in China from 2014 to 2020 to investigate the interaction between the three. It is found that (1) every 1-unit increase in the level of digital economy in the lagged period can cause a 0.008-unit increase in the level of AI application in the current period at the 10% significance level, i.e., the digital economy has a short-term and weakly facilitating effect on AI. (2) Every 1 unit of digital economy level in the lagging period can cause 9.539 units of value added to the sports industry at a 1% significance level. That is, the digital economy has a short-term but strong enhancing effect on the development of the sports industry. (3) Their internal driving force mainly drives the development of digital economy and artificial intelligence, and the self-contribution rate is 72.7% and 91.5% respectively. In contrast, the self-driving force of the sports industry is weaker, and the self-contribution rate is only 68.2%. (4) The contribution rate of the digital economy and artificial intelligence to the development of the sports industry is 12.3% and 19.6% respectively, i.e., the sports industry is more affected by the degree of application of artificial intelligence than the level of development of digital economy.

Head Impact in Blind Football During the Tokyo Paralympics: Video-Based Observational Study

ABSTRACT

Head impacts during blind football are common and have high injury rates; however, their characteristics and impact are still underreported. We compared head impact characteristics in blind football players with and without falls on all 18 official blind football match videos from the Tokyo 2020 Paralympic games. The rate of head impacts with falls was significantly higher in the preliminary phase, offense phase, and during dribbling. Significant differences in the region of the head impacted were also observed among the impact subjects/objects. The findings in this study would contribute to the development of injury prevention measures to minimize head injuries from head impact in blind football.

Biomechanical characteristics of concussive and sub-concussive impacts in youth sports athletes: A systematic review and meta-analysis

This study aimed to quantitatively investigate and report the biomechanical characteristics of concussive and sub-concussive impacts in youth sports. A systematic search was conducted in September 2022 to identify biomechanical impact studies in athletes ≤18 years of age. Twenty-six studies met the inclusion criteria for quantitative synthesis and analysis. DerSimonian Laird random effects model was used to pool data across the included studies. The pooled estimate of mean peak linear and rotational acceleration of concussive impacts in male youth athletes was 85.56 g (95% CI 69.34-101.79) and 4505.58 rad/s² (95% CI 2870.28-6140.98), respectively. The pooled estimate of mean peak linear and rotational acceleration of sub-concussive impacts in youth athletes was 22.89 g (95% CI 20.69-25.08) and 1290.13 rad/s² (95% CI 1050.71-1529.55), respectively. A male vs female analysis in sub-concussive impacts revealed higher linear and rotational acceleration in males and females, respectively. This is the first study to report on impact data in both sexes of youth athletes. Disparity in kinematic impact values suggests future research should aim for standardised measures to reduce heterogeneity in data. Despite this, the data reveals notable impact data that youth athletes are exposed to, suggesting modifications may be required to reduce long-term neurological risks.

Joint regression modelling of intensity and timing of accelerometer counts

Accelerometers are commonly used in human medical and public health research to measure physical movement, which is relevant in a wide range of studies, from physical activity and sleep behaviours studies, to identification of movement patterns in people affected by diseases of the locomotor system and prediction of risk of injury in high performance sports. The accelerometer output provides the intensity (activity count) and timing (timestamp) of the movement, which can be used to define bouts of activity (periods of sustained movement of a given intensity). In some contexts, it may be important to include both dimensions to obtain a broader and deeper understanding of the phenomenon under study. Such is the case of a large-scale epidemiological investigation on the daily and weekly physical activity behaviours of school-aged children enrolled in the UK Millennium Cohort Study, which has motivated the present article. I present a statistical approach to joint modelling of intensity and timing of activity bouts that takes advantage of the circular nature of the timing. The model, which accounts for the longitudinal structure of the observations, is remarkably simple to implement using standard statistical software.

Best Practices for Conducting Physical Reconstructions of Head Impacts in Sport

Physical reconstructions are a valuable methodology for quantifying head kinematics in sports impacts. By recreating the motion of human heads observed in video using instrumented test dummies in a laboratory, physical reconstructions allow for in-depth study of real-world head impacts using well-established surrogates such as the Hybrid III crash test dummy. The purpose of this paper is to review all aspects of the physical reconstruction methodology and discuss the advantages and limitations associated with different choices in case selection, study design, test surrogate, test apparatus, text matrix, instrumentation, and data processing. Physical reconstructions require significant resources to perform and are therefore typically limited to small sample sizes and a case series or case-control study design. Their accuracy may also be limited by a lack of dummy biofidelity. The accuracy, repeatability, and sensitivity of the reconstruction process can be characterized and improved by good laboratory practices and iterative testing. Because wearable sensors have their own limitations and are not available or practical for many sports, physical reconstructions will continue to provide a useful and complementary approach to measuring head acceleration in sport for the foreseeable future.

Analysis of developments and hotspots of international research on sports AI

In this paper, 1,538 papers retrieved with the keywords “sports artificial intelligence (AI)” on the Web of Science database since 2007 were taken as the data source, and the Cite Space V software was used to visualize and analyze them. A visual knowledge graph was used to streamline the countries, institutions and authors conducting sports AI research, discipline distribution, research hotspots and development trends in the past 15 years. Subsequently, its development direction and research progress were discussed. Sports AI was widely distributed, with the US, China and the UK leading the way. The most prolific authors and teams in research on sports AI were concentrated in American universities. Their main research direction is to develop and improve smart wearable devices based on machine learning and deep learning technologies for different groups of people. Research on sports AI involved multiple disciplines, which mainly applied and referred to research methodologies and theories on engineering, computer science and sports science. It could be seen from the frequency and centrality of keywords that in the current field of sports AI, machine learning is the main direction, artificial neural networks is the main algorithm, and practical and empirical research based on data mining is the focus. The research hotspots were divided into three major clusters: physical health promotion, sports injury prevention and control, and athletic performance enhancement. How to introduce intelligent technology into sports for a perfect integration still has an arduous and long way to go. Future development requires joint efforts and participation of scientific researchers, professionals and common people.

A Systematic Review of Head Impacts and Acceleration Associated with Soccer

Epidemiological studies of the neurological health of former professional soccer players are being undertaken to identify whether heading the ball is a risk factor for disease or premature death. A quantitative estimate of exposure to repeated sub-concussive head impacts would provide an opportunity to investigate possible exposure-response relationships. However, it is unclear how to formulate an appropriate exposure metric within the context of epidemiological studies. We have carried out a systematic review of the scientific literature to identify the factors that determine the magnitude of head impact acceleration during experiments and from observations during playing or training for soccer, up to the end of November 2021. Data were extracted from 33 experimental and 27 observational studies from male and female amateur players including both adults and children. There was a high correlation between peak linear and angular accelerations in the observational studies (p < 0.001) although the correlation was lower for the experimental data. We chose to rely on an analysis of maximum or peak linear acceleration for this review. Differences in measurement methodology were identified as important determinants of measured acceleration, and we concluded that only data from accelerometers fixed to the head provided reliable information about the magnitude of head acceleration from soccer-related impacts. Exposures differed between men and women and between children and adults, with women on average experiencing higher acceleration but less frequent impacts. Playing position appears to have some influence on the number of heading impacts but less so on the magnitude of the head acceleration. Head-to-head collisions result in high levels of exposure and thus probably risk causing a concussion. We concluded, in the absence of evidence to the contrary, that estimates of the cumulative number of heading impacts over a playing career should be used as the main exposure metric in epidemiological studies of professional players.

Impact and workload are dominating on-field data monitoring techniques to track health and well-being of team-sports athletes

Participation in sports has become an essential part of healthy living in today's world. However, injuries can often occur during sports participation. With advancements in sensor technology and data analytics, many sports have turned to technology-aided, data-driven, on-field monitoring techniques to help prevent injuries and plan better player management. This review searched three databases, Web of Science, IEEE, and PubMed, for peer-reviewed articles on on-field data monitoring techniques that are aimed at improving the health and well-being of team-sports athletes. It was found that most on-field data monitoring methods can be categorized as either player workload tracking or physical impact monitoring. Many studies covered during this review attempted to establish correlations between captured physical and physiological data, as well as injury risk. In these studies, workloads are frequently tracked to optimize training and prevent overtraining in addition to overuse injuries, while impacts are most often tracked to detect and investigate traumatic injuries. This review found that current sports monitoring practices often suffer from a lack of standard metrics and definitions. Furthermore, existing data-analysis models are created on data that are limited in both size and diversity. These issues need to be addressed to create ecologically valid approaches in the future.

National Athletic Trainers' Association Position Statement: Reducing Intentional Head-First Contact Behavior in American Football Players

OBJECTIVE

To provide evidence-based recommendations for reducing the prevalence of head-first contact behavior in American football players with the aim of reducing the risk of head and neck injuries.

BACKGROUND

In American football, using the head as the point of contact is a persistent, well-documented, and direct cause of catastrophic head and cervical spine injury. Equally concerning is that repeated head-impact exposures are likely to result from head-first contact behavior and may be associated with long-term neurocognitive conditions such as dementia, depression, and chronic traumatic encephalopathy.

CONCLUSIONS

The National Athletic Trainers' Association proposes 14 recommendations to help the certified athletic trainer, allied health care provider, coach, player, parent, and broader community implement strategies for reducing the prevalence of head-first contact in American football.

Career Head Impact Exposure Profile of Canadian University Football Players

This study quantified head impact exposures for Canadian university football players over their varsity career. Participants included 63 players from one team that participated in a minimum of 3 seasons between 2013 and 2018. A total of 127,192 head impacts were recorded from 258 practices and 65 games. The mean (SD) number of career impacts across all positions was 2023.1 (1296.4), with an average of 37.1 (20.3) impacts per game and 7.4 (4.4) impacts per practice. The number of head impacts that players experienced during their careers increased proportionally to the number of athletic exposures (P < .001, r = .57). Linebackers and defensive and offensive linemen experienced significantly more head impacts than defensive backs, quarterbacks, and wide receivers (P ≤ .014). Seniority did not significantly affect the number of head impacts a player experienced. Mean linear acceleration increased with years of seniority within defensive backs and offensive linemen (P ≤ .01). Rotational velocity increased with years of seniority within defensive backs, defensive and offensive linemen, running backs, and wide receivers (P < .05). These data characterize career metrics of head impact exposure for Canadian university football players and provide insights to reduce head impacts through rule modifications and contact regulations.

Analysis of bicycle helmet damage visibility for concussion-threshold impacts

Any helmet involved in an accident should be replaced, regardless of appearance after impact. However, consumer compliance and interpretation of this recommendation is unclear, for which there is additional ambiguity for lesser impacts. This study aims to investigate the relation between helmet damage visibility and lesser impacts in line with concussion. As a preliminary model, a commercially available road-style helmet was chosen. Twelve helmets underwent impact attenuation testing; four were dropped from the standard testing height of 2 m, and eight from lower drop heights (0.34 and 0.42 m) associated with the production of linear accelerations (90 and 100 g, respectively) consistent with the production of concussion. Expanded polystyrene damage was assessed via flat punch penetration testing. American adults were then polled on helmet damage visibility based upon before and after photos. All helmets demonstrated damage to the expanded polystyrene liner in the form of altered material properties. Helmets dropped from 2 m displayed significant changes in elastic buckling (p < .01) and densification behavior (p < .01) as compared with lower drop height results. Adverse change in elastic buckling behavior was found to increase linearly with drop height (p < .001). Damage visibility was significant for helmets dropped from a 2-meter height, however, such a relation among the helmets impacted at the threshold for concussion was lacking. These findings suggest that for the chosen helmet model, consumers may be unable to distinguish between new helmets and helmets with diminished protective abilities.

Head Impact Research Using Inertial Sensors in Sport: A Systematic Review of Methods, Demographics, and Factors Contributing to Exposure

BACKGROUND

The number and magnitude of head impacts have been assessed in-vivo using inertial sensors to characterise the exposure in various sports and to help understand their potential relationship to concussion.

OBJECTIVES

We aimed to provide a comprehensive review of the field of in-vivo sensor acceleration event research in sports via the summary of data collection and processing methods, population demographics and factors contributing to an athlete's exposure to sensor acceleration events.

METHODS

The systematic search resulted in 185 cohort or cross-sectional studies that recorded sensor acceleration events in-vivo during sport participation.

RESULTS

Approximately 5800 participants were studied in 20 sports using 18 devices that included instrumented helmets, headbands, skin patches, mouthguards and earplugs. Female and youth participants were under-represented and ambiguous results were reported for these populations. The number and magnitude of sensor acceleration events were affected by a variety of contributing factors, suggesting sport-specific analyses are needed. For collision sports, being male, being older, and playing in a game (as opposed to a practice), all contributed to being exposed to more sensor acceleration events.

DISCUSSION

Several issues were identified across the various sensor technologies, and efforts should focus on harmonising research methods and improving the accuracy of kinematic measurements and impact classification. While the research is more mature for high-school and collegiate male American football players, it is still in its early stages in many other sports and for female and youth populations. The information reported in the summarised work has improved our understanding of the exposure to sport-related head impacts and has enabled the development of prevention strategies, such as rule changes.

CONCLUSIONS

Head impact research can help improve our understanding of the acute and chronic effects of head impacts on neurological impairments and brain injury. The field is still growing in many sports, but technological improvements and standardisation of processes are needed.

Potential Mechanisms of Acute Standing Balance Deficits After Concussions and Subconcussive Head Impacts: A Review

Standing balance deficits are prevalent after concussions and have also been reported after subconcussive head impacts. However, the mechanisms underlying such deficits are not fully understood. The objective of this review is to consolidate evidence linking head impact biomechanics to standing balance deficits. Mechanical energy transferred to the head during impacts may deform neural and sensory components involved in the control of standing balance. From our review of acute balance-related changes, concussions frequently resulted in increased magnitude but reduced complexity of postural sway, while subconcussive studies showed inconsistent outcomes. Although vestibular and visual symptoms are common, potential injury to these sensors and their neural pathways are often neglected in biomechanics analyses. While current evidence implies a link between tissue deformations in deep brain regions including the brainstem and common post-concussion balance-related deficits, this link has not been adequately investigated. Key limitations in current studies include inadequate balance sampling duration, varying test time points, and lack of head impact biomechanics measurements. Future investigations should also employ targeted quantitative methods to probe the sensorimotor and neural components underlying balance control. A deeper understanding of the specific injury mechanisms will inform diagnosis and management of balance deficits after concussions and subconcussive head impact exposure.

Sports Related Brain Injury and Neurodegeneration in Athletes

Sports deserve a special place in human life to impart healthy and refreshing wellbeing. However, sports activities, especially contact sports, renders athlete vulnerable to brain injuries. Athletes participating in a contact sport like boxing, rugby, American football, wrestling, and basketball are exposed to traumatic brain injuries (TBI) or concussions. The acute and chronic nature of these heterogeneous injuries provides a spectrum of dysfunctions that alters the neuronal, musculoskeletal, and behavioral responses of an athlete. Many sports-related brain injuries go unreported, but these head impacts trigger neurometabolic disruptions that contribute to long-term neuronal impairment. The pathophysiology of post-concussion and its underlying mechanisms are undergoing intense research. It also shed light on chronic disorders like Parkinson's disease, Alzheimer's disease, and dementia. In this review, we examined post-concussion neurobehavioral changes, tools for early detection of signs, and their impact on the athlete. Further, we discussed the role of nutritional supplements in ameliorating neuropsychiatric diseases in athletes.

Group characterization of impact-induced, in vivo human brain kinematics

Brain movement during an impact can elicit a traumatic brain injury, but tissue kinematics vary from person to person and knowledge regarding this variability is limited. This study examines spatio-temporal brain-skull displacement and brain tissue deformation across groups of subjects during a mild impact in vivo. The heads of two groups of participants were imaged while subjected to a mild (less than 350 rad s^-2) impact during neck extension (NE, n = 10) and neck rotation (NR, n = 9). A kinematic atlas of displacement and strain fields averaged across all participants was constructed and compared against individual participant data. The atlas-derived mean displacement magnitude was 0.26 ± 0.13 mm for NE and 0.40 ± 0.26 mm for NR, which is comparable to the displacement magnitudes from individual participants. The strain tensor from the atlas displacement field exhibited maximum shear strain (MSS) of 0.011 ± 0.006 for NE and 0.017 ± 0.009 for NR and was lower than the individual MSS averaged across participants. The atlas illustrates common patterns, containing some blurring but visible relationships between anatomy and kinematics. Conversely, the direction of the impact, brain size, and fluid motion appear to underlie kinematic variability. These findings demonstrate the biomechanical roles of key anatomical features and illustrate common features of brain response for model evaluation.

Head impact forces in blind football are greater in competition than training and increased cervical strength may reduce impact magnitude

Paralympic Blind Association Football has the highest rate of injury of any Paralympic sport and head injuries are common. This study aims to quantify head impact incidence and magnitude in Blind Football, and to examine contributing factors. This Observational study based on a Blind Football Team comprising seven male athletes 28.63 years (SD 9.74, range 16-46) over 6 months. Head mounted impact sensors were used to measure the frequency and location of impacts, as well as their linear acceleration and rotational velocity. Cervical isometric strength and proprioception was measured. There were 374 impacts recorded in 212.5 athlete hours. There was a higher rate of impacts in matches than training (Incidence Risk Ratio 2.58, 95% CI 2.01-3.30). Greater cervical strength was associated with reduced linear acceleration of impacts (R² = 0.1912, p = .020). Blind Football players are exposed to a greater number of head impacts in matches than training. Neck muscle strength may influence magnitude of head impact forces in this sport but further study is required to further investigate.

Player age and initial helmet contact among American football players

OBJECTIVE

Concussions and chronic traumatic encephalopathy (CTE) related to professional football has received much attention within emergency care and sports medicine. Research suggests that some of this may be due to a greater likelihood of initial helmet contact (IHC), however this association has not been studied across all age groups. This study aims to investigate the association between player age and IHC in American football.

METHODS

Retrospective review of championship games between 2016 and 2018 at 6 levels of amateur tackle football as well as the National Football League (NFL). Trained raters classified plays as IHC using pre-specified criteria. A priori power analysis established the requisite impacts needed to establish non-inferiority of the incidence rate of IHC across the levels of play.

RESULTS

Thirty-seven games representing 2912 hits were rated. The overall incidence of IHC was 16% across all groups, ranging from 12.6% to 18.9%. All but 2 of the non-NFL divisions had a statistically reduced risk of IHC when compared with the NFL, with relative risk ratios ranging from 0.55-0.92. IHC initiated by defensive participants were twice as high as offensive participants (RR 2.04, p < 0.01) while 6% [95% CI 5.4-7.2] of all hits were helmet-on-helmet contact.

CONCLUSIONS

There is a high rate of IHC with a lower relative risk of IHC at most levels of play compared to the NFL. Further research is necessary to determine the impact of IHC; the high rates across all age groups suggests an important role for education and prevention.

Neuropsychological Change After a Single Season of Head Impact Exposure in Youth Football

OBJECTIVES

Head impact exposure (HIE) in youth football is a public health concern. The objective of this study was to determine if one season of HIE in youth football was related to cognitive changes.

METHOD

Over 200 participants (ages 9-13) wore instrumented helmets for practices and games to measure the amount of HIE sustained over one season. Pre- and post-season neuropsychological tests were completed. Test score changes were calculated adjusting for practice effects and regression to the mean and used as the dependent variables. Regression models were calculated with HIE variables predicting neuropsychological test score changes.

RESULTS

For the full sample, a small effect was found with season average rotational values predicting changes in list-learning such that HIE was related to negative score change: standardized beta (β) = -.147, t(205) = -2.12, and p = .035. When analyzed by age clusters (9-10, 11-13) and adding participant weight to models, the R2 values increased. Splitting groups by weight (median split), found heavier members of the 9-10 cohort with significantly greater change than lighter members. Additionaly, significantly more participants had clinically meaningful negative changes: X2 = 10.343, p = .001.

CONCLUSION

These findings suggest that in the 9-10 age cluster, the average seasonal level of HIE had inverse, negative relationships with cognitive change over one season that was not found in the older group. The mediation effects of age and weight have not been explored previously and appear to contribute to the effects of HIE on cognition in youth football players.

Evaluating the validity of self-report as a method for quantifying heading exposure in male youth soccer

Assessing heading exposure in football is important when exploring the association between heading and brain alterations. To this end, questionnaires have been developed for use in adult populations. However, the validity of self-report in adolescents remains to be elucidated. Male youth soccer players (n = 34) completed a questionnaire on heading exposure after a two-week period, which included matches and training sessions. Self-reported numbers were compared to observation (considered reference). In total, we observed 157 training sessions and 64 matches. Self-reported heading exposure correlated with observed heading exposure (Spearman's rho 0.68; p < 0.001). Players systematically overestimated their heading exposure by a factor of 3 with the random error of 46%. Area under the curve was 0.87 (95% CI 0.67-1) utilizing self-report for identifying players from high- and low-exposure groups. Thus, in this study, self-reported data could be used to group youth players into high and low heading exposure groups, but not to quantify individual heading exposure.

A Review of On-Field Investigations into the Biomechanics of Concussion in Football and Translation to Head Injury Mitigation Strategies

This review paper summarizes the scientific advancements in the field of concussion biomechanics in American football throughout the past five decades. The focus is on-field biomechanical data collection, and the translation of that data to injury metrics and helmet evaluation. On-field data has been collected with video analysis for laboratory reconstructions or wearable head impact sensors. Concussion biomechanics have been studied across all levels of play, from youth to professional, which has allowed for comparison of head impact exposure and injury tolerance between different age groups. In general, head impact exposure and injury tolerance increase with increasing age. Average values for concussive head impact kinematics are lower for youth players in both linear and rotational acceleration. Head impact data from concussive and non-concussive events have been used to develop injury metrics and risk functions for use in protective equipment evaluation. These risk functions have been used to evaluate helmet performance for each level of play, showing substantial differences in the ability of different helmet models to reduce concussion risk. New advances in head impact sensor technology allow for biomechanical measurements in helmeted and non-helmeted sports for a more complete understanding of concussion tolerance in different demographics. These sensors along with advances in finite element modeling will lead to a better understanding of the mechanisms of injury and human tolerance to head impact.

Managing head injury risks in competitive skateboarding: what do we know?

OBJECTIVES

The broad objective of this paper is to inform policy, practice and research regarding the management of head injury risks in competitive skateboarding. The main motivation for the current study was the question of mandating helmet use in competitive skateboarding. The specific aims are to present current knowledge on (A) head injury risks in skateboarding, (B) preliminary biomechanical data on falls and head injury risks in a selection of competitive skateboarding events similar to those planned for the Summer Olympics, (C) standards for skateboard-styled helmets and (D) impact performance of helmets commonly used in skateboarding.

METHODS

A narrative review of the published literature on head injuries in skateboarding was conducted. Videos of skateboarding competitions from Vans Park Professional League, Street League Skateboarding and Dew Tour were reviewed to describe crashes and falls. Standards databases including the International Organization for Standardization (ISO), British Standards Institution (BSI), Snell, United States Consumer Product Safety Commission (CPSC) and American Society for Testing and Materials (ASTM) were searched for skateboarding-styled helmet standards. A sample of helmets considered suitable for skateboarding was tested in standard impact tests.

RESULTS

The majority of previous literature focused on the paediatric population in a recreational setting with little data from competitive skateboarding. Head injuries comprised up to 75% of all injuries and helmet use was less than 35%. Video analysis identified high rates of falls and crashes during competitive skateboarding, but also a capacity for the athletes to control falls and limit head impacts. Less than 5% of competitive skateboarders wore helmets. In addition to dedicated national skateboard helmet standards, there are several national standards for skateboard-styled helmets. All helmets, with the exception of one uncertified helmet, had similar impact attenuation performance; that is, at 0.8 m drop height, 114-148 g; at 1.5 m, 173-220 g; and at 2.0 m, 219-259 g. Impact performance in the second impact was degraded in all helmets tested.

CONCLUSION

Helmets styled for skateboarding are available 'off the shelf' that will offer protection to the head against skull fractures and intracranial injuries in competitive skateboarding. There is an urgent need to commence a programme of research and development to understanding and control head injury risks.

The Effect of Muscle Activation on Head Kinematics During Non-injurious Head Impacts in Human Subjects

In this study, twenty volunteers were subjected to three, non-injurious lateral head impacts delivered by a 3.7 kg padded impactor at 2 m/s at varying levels of muscle activation (passive, co-contraction, and unilateral contraction). Electromyography was used to quantify muscle activation conditions, and resulting head kinematics were recorded using a custom-fit instrumented mouthpiece. A multi-modal battery of diagnostic tests (evaluated using neurocognitive, balance, symptomatic, and neuroimaging based assessments) was performed on each subject pre- and post-impact. The passive muscle condition resulted in the largest resultant head linear acceleration (12.1 ± 1.8 g) and angular velocity (7.3 ± 0.5 rad/s). Compared to the passive activation, increasing muscle activation decreased both peak resultant linear acceleration and angular velocity in the co-contracted (12.1 ± 1.5 g, 6.8 ± 0.7 rad/s) case and significantly decreased in the unilateral contraction (10.7 ± 1.7 g, 6.5 ± 0.7 rad/s) case. The duration of angular velocity was decreased with an increase in neck muscle activation. No diagnostic metric showed a statistically or clinically significant alteration between baseline and post-impact assessments, confirming these impacts were non-injurious. This study demonstrated that isometric neck muscle activation prior to impact can reduce resulting head kinematics. This study also provides the data necessary to validate computational models of head impact.

Technology Used in the Prevention and Treatment of Shoulder and Elbow Injuries in the Overhead Athlete

PURPOSE OF REVIEW

To review the current technology available for the prevention and treatment of shoulder and elbow injuries in the overhead athlete.

RECENT FINDINGS

Shoulder and elbow injuries are common in recreational and high-level overhead athletes. Injury prevention in these athletes include identifying modifiable risk factors, offering effective preventative training programs, and establishing safe return-to-sport criteria. The advent and use of technologies and wearable devices with concomitant development of software and data analytic programs has significantly changed the role of sports technology in injury identification and prevention. Over the last few decades, leveraging new technologies to better understand and treat patients has become an increasing focus of healthcare. Technologies currently being applied to the treatment of the overhead athlete include kinesiotaping, heart rate monitors, accelerometers/gyroscopes, dynamometers/force plates, camera-based monitoring systems (optical motion analysis), and inertial sensor monitoring units. Advances in technology have made it possible to acquire large amounts of data on athletes that may be used to guide treatment and injury prevention programs; however, literature validating the clinical efficacy of many of these technologies is limited. Further research is needed to continue to allow team physicians to provide better, cost-efficient, and individualized care to the overhead athlete using technology.

Sport-Related Concussion in Female Athletes: A Systematic Review

Background:

Female athletes are more susceptible to sport-related concussions (SRCs) and experience worse outcomes compared with male athletes. Although numerous studies on SRC have compared the outcomes of concussions in male and female athletes after injury, research pertaining to why female athletes have worse outcomes is limited.

Purpose:

To determine the factors that predispose female athletes to more severe concussions than their male counterparts.

Study Design:

Systematic review; Level or evidence, 3.

Methods:

A systematic review was performed according to PRISMA (Preferred Reporting Items for Systematic Meta-Analyses) guidelines. The MEDLINE, EMBASE, CINAHL, PsychINFO, and Cochrane Library databases were systematically searched on July 5 to July 20, 2018. Included were cohort, case-control, and cross-sectional studies that examined the effects of concussive and subconcussive head impacts in only female athletes of all ages, regardless of competition level. These studies were further supplemented with epidemiologic studies. Exclusion criteria included narrative reviews, single case reports, abstracts and letters to the editor, and studies related to chronic traumatic brain injury.

Results:

A total of 25 studies met the inclusion criteria. Female athletes appear to sustain more severe concussions than male athletes, due in part to a lower biomechanical threshold tolerance for head impacts. Additionally, concussions may alter the hypothalamic-pituitary-ovarian axis, resulting in worse symptoms and amenorrhea. Although females are more likely to report concussions than males, underreporting still exists and may result in concussions going untreated.

Conclusion:

This systematic review demonstrates that female athletes may be more susceptible to concussion, have prolonged symptoms after a concussion, and are more likely to report a concussion than their male counterparts. However, underreporting still exists among female athletes. Possible factors that put female athletes at a higher risk for concussions include biomechanical differences and hormonal differences. To effectively prevent, diagnose, and treat concussions in female athletes, more research is required to determine when and how such injuries are sustained. Despite sex-based differences in the clinical incidence, reporting behavior, and outcomes of SRCs, female athletes remain an understudied population, resulting in lack of sex-specific treatment guidelines for female athletes postinjury.

An Investigation of Factors Associated With Head Impact Exposure in Professional Male and Female Australian Football Players

BACKGROUND

Exposure to head acceleration events (HAEs) has been associated with player sex, player position, and player experience in North American football, ice hockey, and lacrosse. Little is known of these factors in professional Australian football. Video analysis allows HAE verification and characterization of important determinants of injury.

PURPOSE

To characterize verified HAEs in the nonhelmeted contact sport of professional Australian football and investigate the association of sex, player position, and player experience with HAE frequency and magnitude.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

Professional Australian football players wore a nonhelmeted accelerometer for 1 match, with data collected across 14 matches. HAEs with peak linear accelerations (PLAs) ≥30g were verified with match video. Verified HAEs were summarized by frequency and median PLA and compared between the sexes, player position, and player experience. Characterization of match-related situations of verified HAEs was conducted, and the head impact rate per skill execution was calculated.

RESULTS

92 male and 118 female players were recruited during the 2017 season. Male players sustained more HAEs (median, 1; IQR, 0-2) than female players (median, 0; IQR, 0-1; P = .007) during a match. The maximum PLAs incurred during a match were significantly higher in male players (median, 61.8g; IQR, 40.5-87.1) compared with female players (median, 44.5g; IQR, 33.6-74.8; P = .032). Neither player position nor experience was associated with HAE frequency. Of all verified HAEs, 52% (n = 110) occurred when neither team had possession of the football, and 46% (n = 98) were caused by contact from another player attempting to gain possession of the football. A subset of HAEs (n = 12; 5.7%) resulted in players seeking medical aid and/or being removed from the match (median PLA, 58.8g; IQR, 34.0-89.0), with 2 (male) players diagnosed with concussion after direct head impacts and associated PLAs of 62g and 75g, respectively. In the setting of catching (marking) the football, female players exhibited twice the head impact rate (16 per 100 marking contests) than male players (8 per 100 marking contests).

CONCLUSION

Playing situations in which players have limited control of the football are a common cause of impacts. Male players sustained a greater exposure to HAEs compared with female players. Female players, however, sustained higher exposure to HAEs than male players during certain skill executions, possibly reflecting differences in skill development. These findings can therefore inform match and skill development in the emerging professional women's competition of Australian football.

The potential of head acceleration measurement to augment current best practice in concussion screening in professional Australian football players

OBJECTIVE

To explore the potential utility of head acceleration event (HAE) measurements to augment identification of players for further concussion screening in non-helmeted contact sport.

DESIGN

Prospective observational pilot study.

PARTICIPANTS

210 (118 female) professional Australian football players in 2017 season.

METHODS

Players wore the X-Patch® accelerometer for one match each with data collected across 14 matches. Players with HAEs above thresholds associated with concussion, 95 g (males) or 85.5 g (females), were compared to players identified to have suspected concussion by club personnel during the inspected matches. Video review of matches was undertaken by a physician blinded to HAEs to identify players with concussive signs.

RESULTS

Among 26 players (50% female) with HAEs above threshold, two players were screened for concussion. Of the remaining 24 players, nine were not visible on video at the HAE time, six sustained verifiable head impacts, and nine sustained verifiable body impacts with no head impacts. Among 184 players with HAEs below threshold, five players were screened.

CONCLUSION

Players were identified to have head impacts and suspected concussion in the absence of HAEs above threshold. Use of X-Patch® was not sufficiently reliable for identifying players for further concussion screening in professional Australian football. Video review of head impacts remains essential in concussion screening.

Cutting to the Pathophysiology Chase: Translating Cutting-Edge Neuroscience to Rehabilitation Practice in Sports-Related Concussion Management

Mild traumatic brain injury, or concussion, is a common sports injury. Concussion involves physical injury to brain tissue and vascular and axonal damage that manifests as transient and often nonspecific clinical symptoms. Concussion diagnosis is challenging, and the relationship between brain injury and clinical symptoms is unclear. The purpose of this commentary was to translate cutting-edge neuroscience to rehabilitation practice. We (1) highlight potential biomarkers that may improve our understanding of concussion and its recovery, (2) explain why researchers must address the paucity of concussion research in female athletes, and (3) present female-specific factors that should be accounted for in future studies. Integrating objective, quantitative measures of concussion pathophysiology with concussion history, genetics, and genomics will help caregivers identify concussed athletes, tailor recovery protocols, and protect athletes from potential long-term effects of cumulative head impact. J Orthop Sports Phys Ther 2019;49(11):811-818. Epub 1 Jun 2019. doi:10.2519/jospt.2019.8884.

A helmetless-tackling intervention in American football for decreasing head impact exposure: A randomized controlled trial

OBJECTIVES

To evaluate a behavioral intervention to reduce head impact exposure in youth playing American football.

DESIGN

Nested randomized controlled trial.

METHODS

Participants, ages 14-17 years, wore head impact sensors (SIM-G™) during two seasons of play. Those randomized to the intervention group underwent weekly tackling/blocking drills performed without helmets (WoH) and shoulder pads while the control group trained as normal, matching frequency and duration. Research personnel provided daily oversight to maintain fidelity. Head impact frequency (≥10g) per athlete exposure (ImpAE) was analyzed over time (two 11-week seasons) using mixed effect models or ANCOVA. Secondary outcomes included exposure-type (training, game) and participation level (entry-level versus upper-level secondary education).

RESULTS

One-hundred fifteen participants (59 WoH, 56 control) met compliance criteria, contributing 47,382 head impacts and 10,751 athlete exposures for analysis. WoH had fewer ImpAE during games compared to control participants at weeks 4 (p=0.0001 season 1, p=0.0005 season 2) and 7 (p=0.0001 both seasons). Upper-level WoH participants had less ImpAE during games than their matched controls at weeks 4 (p=0.017 and p=0.026) and 7 (p=0.037 and p=0.014) in both seasons, respectively. Upper-level WoH also had fewer ImpAE during training at week 7 (p=0.015) in season one.

CONCLUSIONS

Tackling and blocking drills performed without a helmet during training reduced the frequency of head impacts during play, especially during games. However, these differences disappeared by the end of the season. Future research should explore the frequency of behavioral intervention and a dose-response relationship considering years of player experience.

TRIAL REGISTRATION

ClinicalTrials.gov # NCT02519478.

Concussion Pathophysiology and Injury Biomechanics

PURPOSE OF REVIEW

The concussion public health burden has increased alongside our knowledge of the pathophysiology of mild traumatic brain injury (mTBI). The purpose of this review is to summarize our current understanding of mTBI pathophysiology and biomechanics and how these underlying principles correlate with clinical manifestations of mTBI.

RECENT FINDINGS

Changes in post-mTBI glutamate and GABA concentrations seem to be region-specific and time-dependent. Genetic variability may predict recovery and symptom severity while gender differences appear to be associated with the neuroinflammatory response and neuroplasticity. Ongoing biomechanical research has shown a growing body of evidence in support of an "individual-specific threshold" for mTBI that varies based on individual intrinsic factors. The literature demonstrates a well-characterized timeframe for mTBI pathophysiologic changes in animal models while work in this area continues to grow in humans. Current human research shows that these underlying post-mTBI effects are multifactorial and may correlate with symptomatology and recovery. While wearable sensor technology has advanced biomechanical impact research, a definitive concussion threshold remains elusive.

Game-Related Impacts in High School Boys' Lacrosse

Background

The rate of concussions in boys' lacrosse is reported to be the third highest among high school sports in the United States, but no studies have described game-related impacts among boys' lacrosse players.

Purpose

To characterize verified game-related impacts, both overall and those directly to the head, in boys' varsity high school lacrosse.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A total of 77 male participants (mean age, 16.6 ± 1.2 years; mean height, 1.77 ± 0.05 m; mean weight, 73.4 ± 12.2 kg) were instrumented with sensors and were videotaped during 39 games. All verified game-related impacts ≥20g were summarized in terms of frequency, peak linear acceleration (PLA), and peak rotational velocity (PRV). Descriptive statistics and impact rates per player-game (PG) with corresponding 95% CIs were calculated.

Results

Overall, 1100 verified game-related impacts were recorded (PLA: median, 33.5g [interquartile range (IQR), 25.7-51.2]; PRV: median, 1135.5 deg/s [IQR, 790.0-1613.8]) during 795 PGs. The rate for all verified game-related impacts was 1.38 impacts per PG (95% CI, 1.30-1.47). Of these, 680 (61.8%) impacts (PLA: median, 35.9g [IQR, 26.7-55.5]; PRV: 1170.5 deg/s [IQR, 803.2-1672.8]) were directly to the head (impact rate, 0.86 impacts/PG [95% CI, 0.79-0.92]). Overall, midfielders (n = 514; 46.7%) sustained the most impacts, followed by attackers (n = 332; 30.2%), defenders (n = 233; 21.2%), and goalies (n = 21; 1.9%). The most common mechanisms for overall impacts and direct head impacts were contact with player (overall: n = 706 [64.2%]; head: n = 397 [58.4%]) and stick (overall: n = 303 [27.5%]; head: n = 239 [35.1%]), followed by ground (overall: n = 73 [6.6%]; head: n = 26 [3.8%]) and ball (overall: n = 15 [1.4%]; head: n = 15 [2.2%]). Direct head impacts were associated with a helmet-to-helmet collision 31.2% of the time, and they were frequently (53.7%) sustained by the players delivering the impact. Nearly half (48.8%) of players delivering contact used their helmets to initiate contact that resulted in a helmet-to-helmet impact. Players receiving a head impact from player contact were most often unprepared (75.9%) for the collision.

Conclusion

The helmet is commonly used to initiate contact in boys' high school lacrosse, often targeting defenseless opponents. Interventions to reduce head impacts should address rules and coaching messages to discourage intentional use of the helmet and encourage protection of defenseless opponents.

Sport-Related Concussion: Evaluation, Treatment, and Future Directions

Sport-related concussion (SRC) is a highly prevalent injury predominantly affecting millions of youth through high school athletes every year. In recent years, SRC has received a significant amount of attention due to potential for long-term neurologic sequelae. However, the acute symptoms and possibility of prolonged recovery account for the vast majority of morbidity from SRC. Modifying factors have been identified and may allow for improved prediction of a protracted course. Potential novel modifying factors may include genetic determinants of recovery, as well as radiographic biomarkers, which represent burgeoning subfields in SRC research. Helmet design and understanding the biomechanical stressors on the brain that lead to concussion also represent active areas of research. This narrative review provides a general synopsis of SRC, including relevant definitions, current treatment paradigms, and modifying factors for recovery, in addition to novel areas of research and future directions for SRC research.

Evaluation of an In-Ear Sensor for Quantifying Head Impacts in Youth Soccer

BACKGROUND

Wearable sensor systems have the potential to quantify head kinematic responses of head impacts in soccer. However, on-field use of sensors (eg, accelerometers) remains challenging, owing to poor coupling to the head and difficulties discriminating low-severity direct head impacts from inertial loading of the head from human movements, such as jumping and landing.

PURPOSE

To test the validity of an in-ear sensor for quantifying head impacts in youth soccer.

STUDY DESIGN

Descriptive laboratory study.

METHODS

First, the sensor was mounted to a Hybrid III headform and impacted with a linear impactor or a soccer ball. Peak linear acceleration (PLA), peak rotational acceleration (PRA), and peak rotational velocity (PRV) were obtained from both systems; random and systematic errors were calculated with Hybrid III as reference. Then, 6 youth soccer players wore sensors and performed a structured training protocol, including heading and nonheading exercises; they also completed 2 regular soccer sessions. For each accelerative event recorded, PLA, PRA, and PRV outputs were compared with video recordings. Receiver operating characteristic curves were used to determine the sensor's discriminatory capacity in both on-field settings, establishing cutoff values for predicting outcomes.

RESULTS

For the laboratory tests, the random error was 11% for PLA, 20% for PRA, and 5% for PRV; the systematic error was 11%, 19%, and 5%, respectively. For the structured training protocol, heading events resulted in higher absolute values (PLA = 15.6 g± 11.8 g) than nonheading events (PLA = 4.6 g± 1.2 g); the area under the curve was 0.98 for PLA. In regular training sessions, the area under the curve was >0.99 for PLA. A 9 g cutoff value yielded a positive predictive value of 100% in the structured training protocol versus 65% in the regular soccer sessions.

CONCLUSION

The in-ear sensor displayed considerable random error and substantially overestimated head impact exposure. Despite the sensor's excellent on-field accuracy for discriminating headings from other accelerative events in youth soccer, absolute values must be interpreted with caution, and there is a need for secondary means of verification (eg, video analysis) in real-life settings.

CLINICAL RELEVANCE

Wearable sensor systems can potentially provide valuable insights into head impact exposures in contact sports, but their limitations require careful consideration.

An assessment of the utility and functionality of wearable head impact sensors in Australian Football

OBJECTIVES

To assess the utility and functionality of the X-Patch^® as a measurement tool to study head impact exposure in Australian Football. Accuracy, precision, reliability and validity were examined.

DESIGNS

Laboratory tests and prospective observational study.

METHODS

Laboratory tests on X-Patch^® were undertaken using an instrumented Hybrid III head and neck and linear impactor. Differences between X-Patch^® and reference data were analysed. Australian Football players wore the X-Patch^® devices and games were video-recorded. Video recordings were analysed qualitatively for head impact events and these were correlated with X-Patch^® head acceleration events. Wearability of the X-Patch^® was assessed using the Comfort Rating Scale for Wearable Computers.

RESULTS

Laboratory head impacts, performed at multiple impact sites and velocities, identified significant correlations between headform-measured and device-measured kinematic parameters (p<0.05 for all). On average, the X-Patch^®-recorded peak linear acceleration (PLA) was 17% greater than the reference PLA, 28% less for peak rotational acceleration (PRA) and 101% greater for the Head Injury Criterion (HIC). For video analysis, 118 head acceleration events (HAE) were included with PLA ≥30g across 53 players. Video recordings of X-Patch^®-measured HAEs (PLA ≥30g) determined that 31.4% were direct head impacts, 9.3% were indirect impacts, 44.1% were unknown or unclear and 15.3% were neither direct nor indirect head impacts. The X-Patch^® system was deemed wearable by 95-100% of respondents.

CONCLUSIONS

This study reinforces evidence that use of the current X-Patch^® devices should be limited to research only and in conjunction with video analysis.

Laboratory Validation of a Wearable Sensor for the Measurement of Head Acceleration in Men's and Women's Lacrosse

Mild traumatic brain injuries, or concussions, can result from head acceleration during sports. Wearable sensors like the GForceTrackerTM (GFT) can monitor an athlete's head acceleration during play. The purpose of this study was to evaluate the accuracy of the GFT for use in boys' and girls' lacrosse. The GFT was mounted to either a strap connected to lacrosse goggles (helmetless) or a helmet. The assembly was fit to a Hybrid III (HIII) headform instrumented with sensors and impacted multiple times at different velocities and locations. Measurements of peak linear acceleration and angular velocity were obtained from both systems and compared. It was found that a large percent error between the GFT and headform system existed for linear acceleration (29% for helmetless and 123% for helmet) and angular velocity (48% for helmetless and 17% for helmet). Linear acceleration data transformed to the center of gravity (CG) of the head still produced errors (47% for helmetless and 76% for helmet). This error was substantially reduced when correction equations were applied based on impact location (3-22% for helmetless and 3-12% for helmet impacts at the GFT location and transformed to the CG of the head). Our study has shown that the GFT does not accurately calculate linear acceleration or angular velocity at the CG of the head; however, reasonable error can be achieved by correcting data based on impact location.

Characterizing Verified Head Impacts in High School Girls' Lacrosse

BACKGROUND

Girls' high school lacrosse players have higher rates of head and facial injuries than boys. Research indicates that these injuries are caused by stick, player, and ball contacts. Yet, no studies have characterized head impacts in girls' high school lacrosse.

PURPOSE

To characterize girls' high school lacrosse game-related impacts by frequency, magnitude, mechanism, player position, and game situation.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

Thirty-five female participants (mean age, 16.2 ± 1.2 years; mean height, 1.66 ± 0.05 m; mean weight, 61.2 ± 6.4 kg) volunteered during 28 games in the 2014 and 2015 lacrosse seasons. Participants wore impact sensors affixed to the right mastoid process before each game. All game-related impacts recorded by the sensors were verified using game video. Data were summarized for all verified impacts in terms of frequency, peak linear acceleration (PLA), and peak rotational acceleration (PRA). Descriptive statistics and impact rates were calculated.

RESULTS

Fifty-eight verified game-related impacts ≥20 g were recorded (median PLA, 33.8 g; median PRA, 6151.1 rad/s²) during 467 player-games. The impact rate for all game-related verified impacts was 0.12 per athlete-exposure (AE) (95% CI, 0.09-0.16), equivalent to 2.1 impacts per team game, indicating that each athlete suffered fewer than 2 head impacts per season ≥20 g. Of these impacts, 28 (48.3%) were confirmed to directly strike the head, corresponding with an impact rate of 0.05 per AE (95% CI, 0.00-0.10). Overall, midfielders (n = 28, 48.3%) sustained the most impacts, followed by defenders (n = 12, 20.7%), attackers (n = 11, 19.0%), and goalies (n = 7, 12.1%). Goalies demonstrated the highest median PLA and PRA (38.8 g and 8535.0 rad/s², respectively). The most common impact mechanisms were contact with a stick (n = 25, 43.1%) and a player (n = 17, 29.3%), followed by the ball (n = 7, 12.1%) and the ground (n = 7, 12.1%). One hundred percent of ball impacts occurred to goalies. Most impacts occurred to field players within the attack area of the field (n = 32, 55.2%) or the midfield (n = 18, 31.0%). Most (95%) impacts did not result in a penalty.

CONCLUSION

The incidence of verified head impacts in girls' high school lacrosse was quite low. Ball to head impacts were associated with the highest impact magnitudes. While stick and body contacts are illegal in girls' high school lacrosse, rarely did such impacts to the head result in a penalty. The verification of impact mechanisms using video review is critical to collect impact sensor data.

SCAT3 changes from baseline and associations with X2 Patch measured head acceleration in amateur Australian football players

OBJECTIVES

To investigate changes from baseline on SCAT3 as a result of football game exposure, and association with X2 Patch measured head acceleration events in amateur Australian footballers.

DESIGN

Prospective cohort.

METHODS

Peak linear acceleration (PLA) of the head (>10 g) was measured by wearable head acceleration sensor X2 Biosystems X-Patch in male (n=34) and female (n=19) Australian footballers. SCAT3 was administered at baseline (B) and post-game (PG).

RESULTS

1394 head acceleration events (HEA) >10 g were measured. Mean and median HEA PLA were recorded as 15.2 g (SD=9.2, range=10.0-115.8) and 12.4 g (IQR=11.0-15.6) respectively. No significant difference in median HEA PLA (g) was detected across gender (p=0.55), however, more HEAs were recorded in males (p=0.03). A greater number (p=0.004) and severity (p<0.001) of symptoms were reported PG than at B. No significant association between number of HEA or median PLA, and SCAT3 change scores (p>0.05 for all), was identified for either gender.

CONCLUSIONS

Increase in symptom severity post game was not associated with X2 measured HEA. Males sustained more HEA, however HEA PLA magnitude did not differ across gender. Further work on the validation of head acceleration sensors is required and their role in sports concussion research and medical management.

Analysis of head impacts during sub-elite hurling practice sessions

The reported incidence of head and neck injuries in hurling is 0.12 per 1000 hours, but no previous research has quantified head impact characteristics in this sport. Here, a wireless accelerometer and gyroscope captured head impacts, in 20 senior club level hurling players. Peak linear and rotational acceleration and impact location were recorded during three hurling training sessions, each player participating once. A mean of 27.9 impacts (linear acceleration >10g) per player, per session were recorded; 1314 impacts during a total exposure time of 247 minutes. Only 2.6% impacts had peak linear acceleration of >70g and 6.2% had peak rotational acceleration >7900 rad/s². There were significant differences in the number and magnitude of impacts, quantified by the accelerometer, between three training sessions of differing intensity (ŋ2 0.03-0.09, p < 0.001). This study represents a first step in quantifying head impacts during hurling, demonstrating the feasibility of this technology in the field. The sensors were able to discriminate between sessions of varying intensity. These data can be used to develop athlete monitoring protocols and may be useful in developing innovative helmet-testing standards for hurling. The potential for this technology to provide feedback has clinical utility for team medical personnel.

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.