Does cervical muscle strength in youth ice hockey players affect head impact biomechanics?

Gender differences in female and male Australian football concussion injury: A prospective observational study of emergency department presentations

OBJECTIVE

To examine gender differences in Australian football (AF)-related concussion presentations to EDs in regional Australia.

METHODS

A prospective observational study of patients presenting to 1 of the 10 EDs in Western Victoria, Australia, with an AF-related concussion was conducted. Patients were part of a larger study investigating AF injuries over a complete AF season, including pre-season training and practice matches. Information regarding concussion injuries was extracted from patient medical records, including clinical features, concurrent injuries, mechanism and context of injury. Female and male data were compared with chi-squared and Fisher's exact tests. P < 0.05 was considered significant.

RESULTS

From the original cohort of 1635 patients with AF-related injuries (242 female and 1393 male), 231 (14.1%) patients were diagnosed with concussion. Thirty-eight (15.7%) females had concussions versus 193 (13.9%) males (P > 0.05). Females over the age of 16 were more likely to be concussed than males in the same age range (females n = 26, 68.4% vs males n = 94, 48.7%; P = 0.026). Neurosurgically significant head injury was rare (one case). Similar rates of concurrent injury were found between females 15 (39.5%) and males 64 (33.2%), with neck injury the single most common in 24 (10.3%) concussions. Sixty-nine patients (29%) were admitted for observation or to await the results of scans. The majority of concussions occurred in match play (87.9%). Females were more likely injured in contested ball situations (63.2% vs 37.3%; P < 0.05).

CONCLUSION

Concussion rates for community-level AF presentations to regional EDs were similar between genders. Serious head injury was rare, although hospital admission for observation was common. Concurrent injuries were common, with associated neck injury most often identified. Match play accounted for the majority of head injuries.

Brain trauma characteristics for lightweight and heavyweight fighters in professional mixed martial arts

Mixed martial arts (MMA) is a sport where the fighters are at high risk of brain trauma, with characteristics, such as the frequency, magnitude, and interval of head impacts influencing the risk of developing short- and long-term negative brain health outcomes. These characteristics may be influenced by weight class as they may have unique fighting styles. The purpose of this research was to compare frequency, magnitude, and interval of head impacts between lightweight and heavyweight fighters in professional MMA. Frequency, interval, event type, velocity, and location of head impacts were documented for 60 fighters from 15 Lightweight and 15 Heavyweight professional MMA fights. Head impact reconstructions of these events were performed using physical and finite element modelling methods to determine the strain in the brain tissues. The results found that LW and HW fighters sustained similar head impact frequencies and intervals. The LW fighters sustained a significantly higher frequency of very low and high magnitude impacts to the head from punches; HW a larger frequency of high category strains from elbow strikes. These brain trauma profiles reflect different fight strategies and may inform methods to manage and mitigate the long-term effects of repetitive impacts to the head.

Head Kinematics and Injury Analysis in Elite Bobsleigh Athletes Throughout a World Cup Tour

CONTEXT

The neurocognitive health effects of repetitive head impacts have been examined in many sports. However, characterizations of head impacts for sliding-sport athletes are lacking.

OBJECTIVE

To describe head impact kinematics and injury epidemiology in elite athletes during the 2021-2022 Bobsleigh World Cup season.

DESIGN

Cross-sectional study.

SETTING

On-track training and competitions during the Bobsleigh World Cup season.

PATIENTS OR OTHER PARTICIPANTS

Twelve elite bobsleigh athletes (3 pilots [1 female], 9 push athletes [5 females]; age = 30 ± 5 years; female height and weight = 173 ± 8 cm and 75 ± 5 kg, respectively; male height and weight = 183 ± 5 cm and 101 ± 5 kg, respectively).

MAIN OUTCOME MEASURE(S)

Athletes wore an accelerometer-enabled mouthguard to quantify 6-degrees-of-freedom head impact kinematics. Isometric absolute and relative neck strength, number of head acceleration events (HAEs), workload (J), peak linear velocity (m·s-1), peak angular velocity (rad·s-1), peak linear acceleration (g), and peak angular acceleration (rad·s-2) were derived from mouthguard manufacturer algorithms. Linear mixed-effect models tested the effects of sex (male versus female), setting (training versus competition), and position (pilot versus push athlete) on the kinematic variables.

RESULTS

A total of 1900 HAEs were recorded over 48 training and 53 competition days. No differences were found between the number of HAEs per run per athlete by sex (incidence rate ratio [IRR] = 0.82, P = .741), setting (IRR = 0.94, P = .325), or position (IRR = 1.64, P = .463). No sex differences were observed for workload (mean ± SD: males = 3.3 ± 2.2 J, females = 3.1 ± 1.9 J; P = .646), peak linear velocity (males = 1.1 ± 0.3 m·s-1, females = 1.1 ± 0.3 m·s-1; P = .706), peak angular velocity (males = 4.2 ± 2.1 rad·s-1, females = 4.7 ± 2.5 rad·s-1; P = .220), peak linear acceleration (male = 12.4 ± 3.9g, females = 11.9 ± 3.5g; P = .772), or peak angular acceleration (males = 610 ± 353 rad·s-2, females = 680 ± 423 rad·s-2; P = .547). Also, no effects of setting or position on any kinematic variables were seen. Male athletes had greater peak neck strength than female athletes for all neck movements, aside from right-side flexion (P = .085), but no sex differences were noted in relative neck strength.

CONCLUSIONS

We provide a foundational understanding of the repetitive HAEs that occur in bobsleigh athletes. Future authors should determine the effects of repetitive head impacts on neurocognitive function and mental health.

Neck strength alone does not mitigate adverse associations of soccer heading with cognitive performance in adult amateur players

OBJECTIVES

Soccer heading is adversely associated with neurocognitive performance, but whether greater neck strength or anthropometrics mitigates these outcomes is controversial. Here, we examine the effect of neck strength or anthropometrics on associations of soccer heading with neurocognitive outcomes in a large cohort of adult amateur players.

METHODS

380 adult amateur league soccer players underwent standardized measurement of neck strength (forward flexion, extension, left lateral flexion, right lateral flexion) and head/neck anthropometric measures (head circumference, neck length, neck circumference and neck volume). Participants were assessed for heading (HeadCount) and cognitive performance (Cogstate) on up to 7 visits over a period of two years. Principal components analysis (PCA) was performed on 8 neck strength and anthropometric measures. We used generalized estimating equations to test the moderation effect of each of the three PCs on 8 previously identified adverse associations of 2-week and 12-month heading estimates with cognitive performance (psychomotor speed, immediate verbal recall, verbal episodic memory, attention, working memory) and of unintentional head impacts on moderate to severe central nervous system symptoms.

RESULTS

3 principal components (PC's) account for 80% of the variance in the PCA. In men, PC1 represents head/neck anthropometric measures, PC2 represents neck strength measures, and PC3 represents the flexor/extensor (F/E) ratio. In women, PC1 represents neck strength, PC2 represents anthropometrics, and PC3 represents the F/E ratio. Of the 48 moderation effects tested, only one showed statistical significance after Bonferroni correction, which was not robust to extensive sensitivity analyses.

CONCLUSION

Neither neck strength nor anthropometrics mitigate adverse associations of soccer heading with cognitive performance in adult amateur players.

Examining the influence of the Get aHEAD Safely in Soccer™ program on head impact kinematics and neck strength in female youth soccer players

The objective was to examine the efficacy of the Get aHEAD Safely in Soccer™ intervention on head impact kinematics and neck strength in female youth soccer players. The control group (CG) consisted of 13 players (age: 11.0 ± 0.4 yrs), while the experimental group (EG) consisted of 14 players (age: 10.6 ± 0.5 yrs). Head impact kinematics included peak linear acceleration (PLA), peak rotational acceleration (PRA), and peak rotational velocity (PRV). Pre- and post-season measures included strength measures of neck/torso flexion (NF/TF) and extension (NE/TE). Data were analysed using a multilevel linear model and ANOVA techniques. No differences in PLA, PRA, or PRV were observed between groups. The EG showed significant improvement in NF strength while the CG showed significant improvement in NE strength. Both groups significantly improved in TF pre- to post-season. The foundational strength components of the Get aHEAD Safely in Soccer program appear to show a benefit in youth soccer players beginning to learn the skill of purposeful heading.

Exploring the Effects of a Neck Strengthening Program on Purposeful Soccer Heading Biomechanics and Neurocognition

Background

Cervical (neck) strengthening has been proposed as an important factor in concussion prevention. The purpose of the study was to determine if a six-week cervical strengthening program affected neurocognition and purposeful soccer heading biomechanics. The hypothesis was that the neck strengthening program would improve strength, maintain neurocognition, and alter purposeful soccer heading biomechanics.

Study Design

Randomized controlled trial.

Methods

Twenty collegiate soccer athletes (8 males, 12 females, age=20.15±1.35 years, height=171.67±9.01 cm, mass=70.56±11.03 kg) volunteered to participate. Time (pre, post) and group (experimental, control) served as the independent variables. Four composite scores from the CNS Vital Signs computer based neurocognitive test (CNSVS; verbal memory, visual memory, executive function, reaction time) and aspects of heading biomechanics from inertial measurement units (xPatch; peak linear acceleration, peak rotational acceleration, duration, Gadd Severity Index [GSI]) served as the dependent variables. Each athlete completed a baseline measure of neck strength (anterior neck flexors, bilateral anterolateral neck flexors, bilateral cervical rotators) and CNSVS after heading 10 soccer balls at two speeds (11.18 and 17.88 m/s) while wearing the xPatch. The experimental group completed specific cervical neck strengthening exercises twice a week for six weeks using a Shingo Imara™ cervical neck resistance apparatus while the control group did not. After six weeks, the participants completed the same heading protocol followed by measurement of the same outcome variables. The alpha value was set to p<0.05 a priori.

Results

The interaction between time and group was significant for visual memory (F1,17=5.16, p=0.04, η2=0.23). Interestingly, post hoc results revealed visual memory decreased for the control group from pretest (46.90±4.46) compared to posttest (43.00±4.03; mean difference=3.90, 95% CI=0.77-7.03, p=0.02). Interactions for all other dependent variables were not statistically significant (p>0.05).

Conclusions

The cervical neck strengthening protocol allowed maintenance of visual memory scores but did not alter other neurocognitive measures or heading biomechanics. The link between cervical neck strengthening and concussion predisposition should continue to be explored.

Level of Evidence

Level 1b.

Head and Neck Characteristics as Risk Factors For and Protective Factors Against Mild Traumatic Brain Injury in Military and Sporting Populations: A Systematic Review

BACKGROUND

Investigators have proposed that various physical head and neck characteristics, such as neck strength and head and neck size, are associated with protection from mild traumatic brain injury (mTBI/concussion).

OBJECTIVES

To systematically review the literature and investigate potential relationships between physical head and neck characteristics and mTBI risk in athletic and military populations.

METHODS

A comprehensive search of seven databases was conducted: MEDLINE, EMBASE, CINAHL, Scopus, SPORTDiscus, Cochrane Library, and Web of Science. Potential studies were systematically screened and reviewed. Studies on military and athletic cohorts were included if they assessed the relationship between physical head-neck characteristics and mTBI risk or proxy risk measures such as head impact kinematics.

RESULTS

The systematic search yielded a total of 11,723 original records. From these, 22 studies met our inclusion criteria (10 longitudinal, 12 cross-sectional). Relevant to our PECO (Population, Exposure, Comparator, and Outcomes) question, exposures included mTBI incidence and head impact kinematics (acceleration, velocity, displacement) for impacts during sport play and training and in controlled laboratory conditions. Outcome characteristics included head and neck size (circumference, mass, length, ratios between these measures), neck strength and endurance, and rate of force development of neck muscles.

DISCUSSION

We found mixed evidence for head and neck characteristics acting as risk factors for and protective factors against mTBI and increased susceptibility to head impacts. Head-neck strength and size variables were at times associated with protection against mTBI incidence and reduced impact kinematics (14/22 studies found one or more head-neck variable to be associated with protection); however, some studies did not find these relationships (8/22 studies found no significant associations or relationships). Interestingly, two studies found stronger and larger athletes were more at risk of sustaining high impacts during sport. Strength and size metrics may have some predictive power, but impact mitigation seems to be influenced by many other variables, such as behaviour, sex, and impact anticipation. A meta-analysis could not be performed due to heterogeneity in study design and reporting.

CONCLUSION

There is mixed evidence in the literature for the protective capacity of head and neck characteristics. We suggest field-based mTBI research in the future should include more dynamic anthropometric metrics, such as neck stiffness and response to perturbation. In addition, laboratory-based mTBI studies should aim to standardise design and reporting to help further uncover these complicated relationships.

Sex Differences in Neck Strength Force and Activation Patterns in Collegiate Contact Sport

The purpose of this study was to assess changes in cervical musculature throughout contact-heavy collegiate ice hockey practices during a regular season of NCAA Division III ice hockey teams. In this cross-sectional study, 36 (male n = 13; female n = 23) ice hockey players participated. Data were collected over 3 testing sessions (baseline; pre-practice; post-practice). Neck circumference, neck length, head-neck segment length, isometric strength and electromyography (EMG) activity for flexion and extension were assessed. Assessments were completed approximately 1h before a contact-heavy practice and 15 min after practice. For sternocleidomastoid (SCM) muscles, males had significantly greater peak force and greater time to peak force versus females. For both left and right SCMs, both sexes had significantly greater peak EMG activity pre-practice versus baseline, and right (dominant side) SCM time to peak EMG activity was decreased post-practice compared to pre-practice. There were no significant differences for EMG activity of the upper trapezius musculature, over time or between sexes. Sex differences observed in SCM force and activation patterns of the dominant side SCM may contribute to head stabilization during head impacts. Our study is the first investigation to report changes in cervical muscle strength in men's and women's ice hockey players in the practical setting.

Poor isometric neck extension strength as a risk factor for concussion in male professional Rugby Union players

BACKGROUND

Concussion is one of the highest burden injuries within professional Rugby Union ('rugby') and comes with a high health and financial cost to players and teams. Limited evidence exists as to the existence of modifiable intrinsic risk factors for concussion, leaving athletes and clinicians with few options when developing prevention strategies.

OBJECTIVE

To investigate whether neck strength is significantly associated with concussion incidence in professional male rugby players.

METHODS

225 rugby players were assessed for neck strength at three time points throughout the 2018/2019 season using a method of isometric contraction. Associations with clinically diagnosed concussion injuries are presented as incidence rate ratios (IRRs) with 95% CIs.

RESULTS

Thirty concussions occurred in 29 players during the study period; a rate of 13.7 concussions per 1000 hours played. Greater neck strength was observed at mid and end of season time points versus preseason across the study population. There was a significant association between extension strength and concussion; a 10% increase for extension strength was associated with a 13% reduction in concussion rate (adjusted IRR (95% CI) 0.87 (0.78 to 0.98). No other significant associations were observed between concussion incidence and any other unique neck strength range or composite score.

CONCLUSION

Higher neck extension strength is associated with lower concussion rates in male rugby players. Neck strength is a modifiable intrinsic risk factor for concussion and may be an important component of a strength and conditioning regime.

Cervical Muscle Activation Characteristics and Head Kinematics in Males and Females Following Acoustic Warnings and Impulsive Head Forces

Sex, head and neck posture, and cervical muscle preparation are contributing factors in the severity of head and neck injuries. However, it is unknown how these factors modulate the head kinematics. In this study, twenty-four (16 male and 8 female) participants experienced 50 impulsive forces to their heads with and without an acoustic warning. Female participants demonstrated a 71 ms faster (p = 0.002) muscle activation onset compared to males after warning. The magnitude of muscle activation was not significant between sexes. Females exhibited 21% (p < 0.008) greater peak angular velocity in all force directions and 18% (p < 0.04) greater peak angular acceleration in sagittal plane compared to males. Females exhibited 15% (p = 0.03) greater peak linear acceleration compared to males only in sagittal flexion. Preparation attenuated head kinematics significantly (p < 0.03) in 11 out of 18 investigated head kinematics for both sexes. A warning eliciting a startle response 420 ms prior to the impact resulted in significant attenuation of all measured head kinematics in sagittal extension (p < 0.037). In conclusion, both sex and warning type were significant factors in head kinematics. These data provide insight into the complex relationship of muscle activation and sex, and may help identify innovative strategies to reduce head and neck injury risk in sports.

Head Accelerations during a 1-on-1 Rugby Tackling Drill Performed by Experienced Rugby Union Players

Rugby Union is a popular sport played by males and females worldwide, from junior to elite levels. The highly physical skill of tackling occurs every few seconds throughout a match and various injuries associated with tackling are relatively common. Of particular interest are head injuries that result in a concussion. Recently, repeated non-injurious head impacts in sport have attracted the attention of researchers interested in brain health. Therefore, this study assessed head movement during repeated rugby tackle drills among experienced Rugby Union players. Experienced male and female participants performed 15 1-on-1 tackles in a motion analysis laboratory to measure the head movements of the ball carrier and tackler during each tackle, using three-dimensional motion capture. The average peak acceleration of the head for ball carriers was 28.9 ± 24.08 g and 36.67 ± 28.91 g for the tacklers. This study found that the type of head impacts common while performing a tackle in Rugby Union are similar to those experienced by soccer players during heading, which has been found to alter brain function that lasts hours after the event. This has important implications for player health and suggests that mitigation strategies should be considered for Rugby Union.

The role of neck muscle co-contraction and postural changes in head kinematics after safe head impacts: Investigation of head/neck injury reduction

Concerns surrounding concussions from impacts to the head necessitate research to generate new knowledge about ways to prevent them and reduce risk. In this paper, we report the relative temporal characteristics of the head resulting from neck muscle co-contraction and postural changes following a sudden force applied to the head in four different directions. In the two "prepared" conditions (i.e., co-contraction and postural), participants experienced impulsive forces to the head after hearing a warning. The warning given for the postural condition informed both the direction and timing of the impulsive force. Participants responded to the postural warning by altering their head posture, whereas in the co-contraction warning, the force direction was unknown to them, and they were asked to isometrically co-contract their neck muscles after the warning. Peak angular velocity reduced by 29% in sagittal extension, 18% in sagittal flexion, and 23% in coronal lateral flexion in prepared vs. unwarned conditions. Peak linear acceleration was attenuated by 15% in sagittal extension, 8% in sagittal flexion, and 18% in coronal lateral flexion in prepared vs. unwarned conditions. Changes in peak angular acceleration were not uniform. We also measured a significant delay in the peak angular velocity (22 vs. 44.8 ms) and peak angular acceleration (7 vs. 20 ms) after peak linear acceleration in prepared compared to unwarned conditions. An increase in muscle activation significantly reduced the peak angular velocity and linear acceleration. Gross head movement was significantly decreased with preparation. These findings suggest that a warning prior to impact can reduce head kinematics associated with injury.

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.

An Accessible, 16-Week Neck Strength Training Program Improves Head Kinematics Following Chest Perturbation in Young Soccer Athletes

CONTEXT

Neck size and strength may be associated with head kinematics and concussion risks. However, there is a paucity of research examining neck strengthening and head kinematics in youths. In addition, neck training is likely lacking in youth sport due to a perceived inadequacy of equipment or time.

OBJECTIVE

Examine neck training effects with minimal equipment on neck strength and head kinematics following chest perturbations in youth athletes.

DESIGN

Single-group, pretest-posttest case series.

SETTING

Athlete training center.

PARTICIPANTS

Twenty-five (14 men and 11 women) youth soccer athletes (9.8 [1.5] y).

INTERVENTION

Sixteen weeks of twice-weekly neck-focused resistance training utilizing bands, body weight, and manual resistance.

MAIN OUTCOME MEASURES

Head kinematics (angular range of motion, peak anterior-posterior linear acceleration, and peak resultant linear acceleration) were measured by an inertial motion unit fixed to the apex of the head during torso perturbations. Neck-flexion and extension strength were assessed using weights placed on the forehead and a plate-loaded neck harness, respectively. Neck length and circumference were measured via measuring tape.

RESULTS

Neck extension (increase in median values for all: +4.5 kg, +100%, P < .001; females: +4.5 kg, +100%, P = .002; males: +2.2 kg, +36%, P = .003) and flexion (all: +3.6 kg, +114%, P < .001; females: +3.6 kg, +114%, P = .004; males: +3.6 kg, +114%, P = .001) strength increased following the intervention. Men and women both experienced reduced perturbation-induced head pitch (all: -84%, P < .001). However, peak resultant linear acceleration decreased in the female (-53%, P = .004), but not male (-31%, P = 1.0) subgroup. Preintervention peak resultant linear acceleration and extension strength (R2 = .21, P = .033) were the closest-to-significance associations between head kinematics and strength.

CONCLUSIONS

Young athletes can improve neck strength and reduce perturbation-induced head kinematics following a 16-week neck strengthening program. However, further research is needed to determine the effect of improved strength and head stabilization on concussion injury rates.

Sex and posture dependence of neck muscle size-strength relationships

Neck muscle size and strength have been linked to lower injury risk and reduced pain. However, prior findings have been inconclusive and have failed to clarify whether there are sex differences in neck muscle size-strength relationships. Such differences may point to an underlying cause for the reported sex difference in neck pain prevalence. Thirty participants (13 males, 17 females) who underwent neck strength testing and MR imaging were analyzed. Strength was measured in three conditions that differed in posture and exertion direction. Muscle size was quantified by three metrics: anatomical cross-sectional area (ACSA), muscle volume (MV), and an estimate of physiological cross-sectional area-reconstruction-based cross-sectional area (RCSA). Inter-posture strength correlations, muscle size-strength correlations, and sex differences were analyzed with linear regression. Males were approximately 65% stronger and had significantly larger muscles. Strength varied significantly across postures, but only female strength values for different postures were significantly correlated. Observed in males only, the sternocleidomastoid (SCM) was a strong predictor of flexion strength in the neutral posture while the anterior scalene (AS) was more involved in the extended. No extensor's size was significantly linked to extension strength. A greater amount of force variation is unexplained by muscle size alone in females than in males. Males and females exhibited distinct size-strength relationships, highlighting the need for sex-specific models and analyses and the greater potential effect of non-morphometric factors on force generating capacity in females. No advantage of one muscle size metric over another in strength prediction was evidenced.

Injury Reduction Programs for Reducing the Incidence of Sport-Related Head and Neck Injuries Including Concussion: A Systematic Review

BACKGROUND

Sport-related head and neck injuries, including concussion, are a growing global public health concern with a need to explore injury risk reduction strategies such as neck exercises.

OBJECTIVES

To systematically review the literature to investigate: (1) the relationship between neck strength and sport-related head and neck injuries (including sport-related concussion (SRC); and (2) whether neck exercise programs can reduce the incidence of (a) sport-related head and neck injuries; and (b) SRC.

METHODS

Five databases (Ovid MEDLINE, CINAHL, EMBASE, SPORTDiscus, and Web of Science) and research lists of included studies were searched using a combination of medical subject headings and keywords to locate original studies which reported the association between incidence of head and/or neck injury and neck strength data, or included a neck exercise intervention either in isolation or as part of a more comprehensive exercise program.

RESULTS

From an initial search of 593 studies, six were included in this review. A narrative synthesis was performed due to the heterogeneity of the included studies. The results of two observational studies reported that higher neck strength, but not deep neck flexor endurance, is associated with a lower risk of sustaining a SRC. Four intervention studies demonstrated that injury reduction programs that included neck exercises can reduce the incidence of sport-related head and neck injuries including SRC.

CONCLUSION

Consideration should be given towards incorporating neck exercises into injury reduction exercise programs to reduce the incidence of sport-related head and neck injuries, including SRC.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO (registration number: 194217).

Physical Conditioning Strategies for the Prevention of Concussion in Sport: a Scoping Review

BACKGROUND

Concussion in sports has received a great deal of media attention and may result in short and longer-lasting symptoms, especially in adolescents. Although significant strides have been made in the identification and management of concussion, less is known about the primary prevention of this condition. The aims of this scoping review are to (1) summarize the current research of physical conditioning strategies to reduce or prevent concussion incidence in individuals participating in sport, especially adolescents, and (2) to identify gaps in the knowledge base. Our research question was what is known from the existing literature about physical preparation strategies to reduce or prevent concussion in adult and adolescent sports?

METHODS

Three literature searches were conducted by information officers at two universities at six-month intervals, using five electronic databases (PubMed; WorldCat.org ; Mendeley; EBSCOHost and Ovid MEDLINE). To increase the search range, subject experts were consulted and articles and reference lists were hand searched. A scoping review methodology identified eligible studies that analyzed physical preparation techniques on modifiable physical risk factors in athletes to reduce the incidence of concussion. The PRISMA-ScR checklist guided the reporting of the findings.

RESULTS

A total of 1414 possible articles were identified, after duplicates removed, and articles analyzed against the inclusion and exclusion criteria, only 9 articles qualified for analysis. Two articles were found from studying reference lists. Thus, a total of 11 articles were included in the final evaluation for the purposes of this study. Data are reported from mostly adolescent subjects participating in nine different sports from three countries. Findings are presented with specific reference to previously recognized modifiable risk factors of concussion which include neck strength, neck size, cervical stiffness, type of sport, and pre-activity exercises.

CONCLUSIONS

There is limited research examining the physical preparation of athletes, especially in adolescents, to reduce or prevent concussion, and conflicting evidence in the few small sample studies that were identified. This scoping review identifies the research gap for a potentially vital modifiable risk factor, notably in the physical preparation of children and adolescents to reduce or prevent sports-related concussion.

The relation between neck strength and psychological distress: preliminary evidence from collegiate soccer athletes

AIM

To examine whether neck strength and symmetry are associated with psychological function in athletes with exposure to repetitive head impacts.

METHODS

Collegiate soccer (n = 29) and limited/noncontact (n = 63) athletes without a history of concussion completed the Brief Symptom Inventory 18 and assessments of isometric neck strength. Neck strength symmetry was calculated as the difference in strength between opposing muscle groups.

RESULTS

The results demonstrated that lower neck strength was associated with more symptoms of anxiety, whereas asymmetry in neck strength was associated with more symptoms of somatization and depression in soccer athletes only.

CONCLUSION

These preliminary results suggest that greater neck strength/symmetry is related to better psychological function in athletes who have higher exposure to repetitive head impacts.

Proceedings From the Ice Hockey Summit III: Action on Concussion

OBJECTIVES

The Ice Hockey Summit III provided updated scientific evidence on concussions in hockey to inform these 5 objectives: (1) describe sport related concussion (SRC) epidemiology; (2) classify prevention strategies; (3) define objective, diagnostic tests; (4) identify treatment; and (5) integrate science and clinical care into prioritized action plans and policy.

METHODS

Our action plan evolved from 40 scientific presentations. The 155 attendees (physicians, athletic trainers, physical therapists, nurses, neuropsychologists, scientists, engineers, coaches, and officials) voted to prioritize these action items in the final Summit session.

RESULTS

To (1) establish a national and international hockey database for SRCs at all levels; (2) eliminate body checking in Bantam youth hockey games; (3) expand a behavior modification program (Fair Play) to all youth hockey levels; (4) enforce game ejection penalties for fighting in Junior A and professional hockey leagues; (5) establish objective tests to diagnose concussion at point of care; and (6) mandate baseline testing to improve concussion diagnosis for all age groups.

CONCLUSIONS

Expedient implementation of the Summit III prioritized action items is necessary to reduce the risk, severity, and consequences of concussion in the sport of ice hockey.

The Influence of Neck Stiffness on Head Kinematics and Maximum Principal Strain Associated With Youth American Football Collisions

Understanding the relationship between head mass and neck stiffness during direct head impacts is especially concerning in youth sports where athletes have higher proportional head mass to neck strength. This study compared 2 neck stiffness conditions for peak linear and rotational acceleration and brain tissue deformations across 3 impact velocities, 3 impact locations, and 2 striking masses. A pendulum fitted with a nylon cap was used to impact a fifth percentile hybrid III headform equipped with 9 accelerometers and fitted with a youth American football helmet. The 2 neck stiffness conditions consisted of a neckform with and without resistance in 3 planes, representing the upper trapezius, the splenius capitis, and the sternocleidomastoid muscles. Increased neck stiffness resulted in significant changes in head kinematics and maximum principal strain specific to impact velocity, impact location, and striking mass.

A Systematic Review of Strength and Conditioning Protocols for Improving Neck Strength and Reducing Concussion Incidence and Impact Injury Risk in Collision Sports; Is There Evidence?

The objective of this systematic literature review was to evaluate the evidence regarding the development of neck strength in reducing concussion and cervical spine injuries in adult amateur and professional sport populations. PubMed, CINAHL, Science Direct, and Web of Science databases were searched systematically. The criteria for inclusion in the review were as follows: (1) a human adult (≥18 or above); (2) involved in amateur, semi-professional, or professional sports; (3) sports included involved collisions with other humans, apparatus or the environment; (4) interventions included pre- and post-neck muscle strength measures or neck stability measures; (5) outcomes included effects on increasing neck strength in participants and/or injury incidence. Database searches identified 2462 articles. Following title, abstract, and full paper screening, three papers were eligible for inclusion. All of the papers reported information from male participants, two were focused on rugby union, and one on American football. Two of the included studies found a significant improvement in isometric neck strength following intervention. None of the studies reported any impact of neck strengthening exercises on cervical spine injuries. This review has shown that there is currently a lack of evidence to support the use of neck strengthening interventions in reducing impact injury risk in adult populations who participate in sport.

Isometric Cervical Muscular Strength in Pediatric Athletes With Multiple Concussions

OBJECTIVE

To compare maximal cervical muscle strength among athletes with a history of 2 or more concussions relative to athletes with no history of a previous concussion.

DESIGN

Athletes in the 2 groups were frequency-matched. Linear mixed models were used to test for differences in peak isometric flexion, extension, left lateral flexion, and right lateral flexion cervical muscle torque between groups.

SETTING

Pediatric sports medicine clinic.

PARTICIPANTS

Athletes with a history of multiple concussions (n = 16) and athletes with no previous concussion history (n = 17). INTERVENTIONS (OR ASSESSMENT OF RISK FACTORS OR INDEPENDENT VARIABLES):: Concussion history (group), age, sex, neck girth, and height.

MAIN OUTCOME MEASURES

Peak isometric torque measured with a stationary isokinetic dynamometer during a 3-second isometric hold.

RESULTS

There was no significant difference in peak flexion [mean difference: 21.2%, 95% confidence interval (CI): -6.6% to 57.4%, P = 0.1413], extension (mean difference: 17%, 95% CI, -6.8% to 47.1%, P = 0.1667), left lateral (mean difference: 4.4%, 95% CI, -16.9% to 31.1%, P = 0.7011), or right lateral (mean difference: 9.3%, 95% CI, -14.5% to 39.8%, P = 0.4627) isometric torque in the concussion group relative to the control group. Across all muscle actions, neck torque was significantly (P < 0.05) higher in male compared with female athletes. Increasing neck girth was also associated with a significant (P < 0.05) increase in neck torque.

CONCLUSIONS

There was no evidence of a consistent cervical muscle strength deficit among athletes with a history of 2 or more concussions relative to athletes with no previous history of a concussion. Age, neck girth, and sex were significantly associated with cervical muscle strength.

CLINICAL RELEVANCE

Isometric cervical muscle strength testing may not be a reliable test for differentiating athletes with a history of multiple concussions relative to athletes with no history of concussions in the pediatric and adolescent population. Our study presents a reliable methodology for testing cervical muscle strength among young athletes.

Heading-Related Slowing by Twenty-Four Hours in Youth Athletes

Research suggests cumulative effects of repetitive head impacts (RHIs) on brain structure, especially with younger age of first exposure. Further, recent evidence suggests no immediate cognitive changes with increased RHIs but impairments across a sports season. The aim was to examine more closely the short-term time course of behavioral effects of exposure to RHI. Across 2 years, 18 female adolescent soccer players were tested on ProPoint (sensorimotor) and AntiPoint (cognitive) tasks with reaction time (RT) being the main outcome measure. The athletes were tested before and after workout with ball heading (immediate effect), as well as 24 h after workout (24 h effect) throughout two consecutive seasons. The number of headers performed 24 h before workout, during workout, and season average per workout were recorded. The athletes showed a decrease in ProPoint and AntiPoint RTs immediately after a workout, with no change or decrease in RTs with increasing RHIs. However, increasing RHIs during workout increased RTs in both tasks when tested 24 h later. The athletes also showed an increase in AntiPoint RTs with increasing season average RHIs. Our findings show a complex time course of effects of RHIs on sensorimotor and cognitive performance in adolescent athletes, with exposure to RHIs associated with no change or immediate benefits and then deficits by 24 h. Pathophysiological changes associated with exercise and traumatic brain injury can account for the sensorimotor and cognitive performance changes occurring within 24 h after RHIs.

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.

A Novel Testing Device to Assess the Effect of Neck Strength on Risk of Concussion

Concussion awareness has become more prevalent in the past decade, leading to growing calls for prevention programs such as neck strengthening. However, previous research work has shown that not all training programs have been effective, and there is a need for a reliable testing device to measure cervical strength dynamically before and after training. Therefore, this work proposes a novel Concussion Active Prevention Testing Device composed of inertial measurement units mounted on the head and a custom-designed frame to measure head kinematics during controlled sub-concussive impacts. Through an experimental study with able-bodied participants, the proposed testing device demonstrated high intra-participant repeatability between waveforms of the head acceleration and angular velocity in the sagittal plane (multiple correlation coefficient of 80%). Similarly, good and excellent intra-class correlation coefficients were obtained for head injury metrics, including range, peak, Gadd severity index, head injury criterion, and range of motion. Finally, the results showed that significantly higher head injury metrics were measured for female participants, which was in line with the findings of previous research works. We conclude that the proposed testing device can be used to measure repeatable and informative metrics for evaluating the effectiveness of athletes' neck strengthening program.

Concussion-Prevention Strategies Used in National Collegiate Athletic Association Divisions I and II Women's Soccer

CONTEXT

Whereas much attention has been paid to identifying mechanisms for decreasing concussion rates in women's soccer players, which strategies are currently being used is unknown. In addition, athletic trainers' (ATs') knowledge and beliefs about the efficacy of concussion-prevention practices have not been studied.

OBJECTIVES

To evaluate the concussion-prevention strategies being used in National Collegiate Athletic Association Division I and Division II women's soccer and identify the beliefs of certified ATs regarding mechanisms for preventing concussion.

DESIGN

Cross-sectional study.

SETTING

Online survey.

PATIENTS OR OTHER PARTICIPANTS

A total of 223 women's soccer team ATs employed at Division I or II universities.

MAIN OUTCOME MEASURE(S)

A survey instrument of structured questions and open-ended, follow-up questions was developed to identify the use of cervical-strengthening programs, headgear, and other techniques for preventing concussion. Questions also addressed ATs' beliefs regarding the effectiveness of cervical strengthening, headgear, and mouthguards in concussion prevention. Data were collected via questionnaire in Qualtrics survey software. Descriptive statistics of frequencies and percentages were calculated for close-ended questions. Open-ended questions were evaluated for common themes, which were then reported by response frequency.

RESULTS

Cervical strengthening or stability for concussion prevention was reported by 38 (17.12%) respondents; 153 (69.86%) ATs believed that cervical strengthening would aid in concussion prevention. Seventy-eight (35.49%) reported that their players wore headgear. Nineteen (8.76%) believed that soccer headgear prevented concussions; 45 (20.74%) believed that mouthguards prevented concussions. Education in proper soccer technique was reported by 151 (69.59%) respondents. Fourteen (0.06%) respondents cited nutritional strategies for concussion prevention.

CONCLUSIONS

Although ATs believed that cervical strengthening could help prevent concussions, few had implemented this strategy. However, the ATs whose teams used headgear outnumbered those who believed that headgear was an effective prevention strategy. Based on our findings, we saw a disconnect among the current use of concussion-prevention strategies, ATs' beliefs, and the available evidence.

Sensitivity analysis of muscle properties and impact parameters on head injury risk in American football

Head injuries frequently occur in American football and other contact sports. Uncertainty on the effects of cervical muscle properties on head injury risk may be due to the limitations of previous observational studies. This simulation study employs a musculoskeletal model of the head and neck to investigate the effect of several factors related to head injury metrics in American Football. These factors include isometric muscle strength, the eccentric multiplier (which is related to the athlete's ability to apply greater muscle force during eccentric contractions), posture, muscle activation patterns, and impact properties. Impact properties were based on the literature and tuned to reproduce peak linear and rotational accelerations of the skull. We hypothesized that active neck muscles significantly reduce head injury metrics. We systematically altered each model parameter to test our hypothesis. We then determined which model parameters affect head injury metrics the most. The results of this study indicate that active neck muscles have a statistically significant effect on head injury metrics. Increasing muscle strength and eccentric multiplier also resulted in a statistically significant reduction of head injury metrics. However, posture prior to impact had a much stronger effect than any other factor on head injury metrics. A comprehensive approach to athlete training protocols is recommended, including exercises aimed at increasing eccentric muscle strength and preparation for impacts. Future studies should investigate how targeted muscle strengthening and impact training (i.e. activation patterns and posture) modifies risk.

Head Impact Biomechanics Differ Between Girls and Boys Youth Ice Hockey Players

The influence of sex on head impact biomechanics is unknown for youth ice hockey. We sought to determine sex differences in head impact severity and frequency in youth ice hockey players. Male (n = 110) and female (n = 25) players (13-16 years old) were recruited from a local hockey organization. Players wore helmets instrumented with the Head Impact Telemetry System for all competitions and practices throughout the season. Seven team-seasons were captured. Random intercepts general mixed linear models determined whether linear acceleration and rotational acceleration differed by sex. Linear regression models evaluated the relationship between sex and impact frequency. All head impact biomechanics were natural log-transformed as their distributions were right-skewed. Females sustained fewer impacts per player than males (27 fewer impacts per player-season, p < 0.0001) even when analysis was limited to games only (21 fewer impacts per player-season, p < 0.0001). The linear acceleration was higher among females (1.07 g; 95% CI 1.00, 1.13; p = 0.04). There were no other meaningful sex differences in head impact severity. Female players are not permitted to body check, and this likely explains why they sustain fewer head impacts than males. However, as a result, females likely sustain a higher proportion of head impacts through illegal or unintentional head contact, and these impacts may result in more force being delivered to the head.

Exploring the role of cervical spine endurance as a predictor of concussion risk and recovery following sports related concussion

BACKGROUND

Concussions have become a significant public health concern with rising incidence rates. Concussions have been shown to occur concurrently with neck injuries, such as whiplash-associated-disorder, therefore, understanding the role of the neck in concussions is important.

OBJECTIVES

To determine if there is a relationship between cervical muscle endurance and either concussion incidence, or concussion recovery in university athletes. Specifically, the primary aim was to investigate a relationship between pre-season deep neck flexor endurance test (DNFET) time in those who sustained an in-season injury versus those who did not. The secondary aim is to determine correlation in DNFET times and concussion recovery.

DESIGN

Longitudinal observational study.

METHODS

Pre-season DNFET was performed on university athletes. In the event of a concussion, cervical endurance and neuromuscular adaptation was re-assessed with the DNFET. Rehabilitative exercises were prescribed, as required, and DNFET was measured at subsequent treatments.

RESULTS

There was no significant difference between pre-season DNFET times and concussion incidence (p = 0.55). However, there was a moderate correlation between DNFET times and concussion recovery (R = 0.47, p = 0.001) whereby DNFET times improved predictively throughout rehabilitation.

CONCLUSIONS

While no statistically significant relationship was found between DNFET and concussion incidence, a significant clinical relationship was present with recovery. The validity of the DNFET test as a means for assessing risk or measuring recovery requires additional research.

Passive cervical spine ligaments provide stability during head impacts

It has been suggested that neck muscle strength and anticipatory cocontraction can decrease head motions during head impacts. Here, we quantify the relative angular impulse contributions of neck soft tissue to head stabilization using an OpenSim musculoskeletal model with Hill-type muscles and rate-dependent ligaments. We simulated sagittal extension and lateral flexion mild experimental head impacts performed on 10 subjects with relaxed or cocontracted muscles, and median American football head impacts. We estimated angular impulses from active muscle, passive muscle and ligaments during head impact acceleration and deceleration phases. During the acceleration phase, active musculature produced resistive angular impulses that were 30% of the impact angular impulse in experimental impacts with cocontracted muscles. This was reduced below 20% in football impacts. During the deceleration phase, active musculature stabilized the head with 50% of the impact angular impulse in experimental impacts with cocontracted muscles. However, passive ligaments provided greater stabilizing angular impulses in football impacts. The redistribution of stabilizing angular impulses results from ligament and muscle dependence on lengthening rate, where ligaments stiffen substantially compared to active muscle at high lengthening rates. Thus, ligaments provide relatively greater deceleration impulses in these impacts, which limit the effectiveness of muscle strengthening or anticipated activations.

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.

The Role of Neck Musculature in Traumatic Brain Injuries in Older Adults: Implications From Sports Medicine

Traumatic brain injuries (TBIs) are common and serious injuries to older adults. The majority of TBIs in older adults are sustained when the head impacts the ground or other surface during a fall. While several non-modifiable risk factors have been identified for fall-related TBIs in older adults, there still remains a dearth of knowledge surrounding modifiable risk factors. Thus, this significant knowledge gap warrants an investigation into research across disciplines. The sports medicine literature has examined several modifiable risk factors to prevent a mild form of TBI known as concussion. While this research has identified several risk factors, one particular risk factor may have potential implications to fall-related TBIs in older adults. The sports medicine literature has shown that decreased neck strength and slower neck muscle activation are significant predictors for sports-related concussion. Similarly, older adults experience age-related declines to neck muscle strength and muscle activation. Consequently, these age-related declines to the neck musculature may result in the inability of older adults to control their head during a fall, which results in greater impact forces being transmitted to the brain and increases the risk of TBI. This perspective article assesses the sports medicine literature related to the implications of neck strength and muscle activation in sports-related concussion, discusses age-related declines to neck strength and muscle activation, and highlights the potential impact of the neck musculature on fall-related TBIs in older adults.

Verifying Head Impacts Recorded by a Wearable Sensor using Video Footage in Rugby League: a Preliminary Study

BACKGROUND

Rugby league is a full-contact collision sport with an inherent risk of concussion. Wearable instrumented technology was used to observe and characterize the level of exposure to head impacts during game play.

PURPOSE

To verify the impacts recorded by the x-patch™ with video analysis.

STUDY DESIGN

Observational case series.

METHODS

The x-patch™ was used on eight men's semi-professional rugby league players during the 2016 Newcastle Rugby League competition (five forwards and three backs). Game day footage was recorded by a trained videographer using a single camera located at the highest midfield location to verify the impact recorded by the x-patch™. Videographic and accelerometer data were time synchronized.

RESULTS

The x-patch™ sensors recorded a total of 779 impacts ≥ 20 g during the games, of which 732 (94.0%) were verified on video. In addition, 817 impacts were identified on video that did not record an impact on the sensors. The number of video-verified impacts ≥ 20 g, per playing hour, was 7.8 for forwards and 4.8 for backs (range = 3.9-19.0). Impacts resulting in a diagnosed concussion had much greater peak linear acceleration (M = 76.1 g, SD = 17.0) than impacts that did not result in a concussion (M = 34.2g, SD = 18.0; Cohen's d = 2.4).

CONCLUSIONS

The vast majority (94%) of impacts ≥ 20 g captured by the x-patch™ sensor were video verified in semi-professional rugby league games. The use of a secondary source of information to verify impact events recorded by wearable sensors is beneficial in clarifying game events and exposure levels.

Head Injury in Soccer: From Science to the Field; summary of the head injury summit held in April 2017 in New York City, New York

There has been an increased focus and awareness of head injury and sport-related concussion (SRC) across all sports from the medical and scientific communities, sports organisations, legislators, the media and the general population. Soccer, in particular, has been a focus of attention due to the popularity of the game, the frequency of SRC and the hypothesised effects of repetitive heading of the ball. Major League Soccer, US Soccer and the National Women’s Soccer League jointly hosted a conference entitled, ‘Head Injury in Soccer: From Science to the Field’, on 21–22 April 2017 in New York City, New York. The mission of this conference was to identify, discuss and disseminate evidence-based science related to the findings and conclusions of the fifth International Conference on Concussion in Sport held by the Concussion in Sport Group and apply them to the sport of soccer. In addition, we reviewed information regarding the epidemiology and mechanism of head injuries in soccer at all levels of play, data regarding the biomechanics and effects of repetitive head impacts and other soccer-specific considerations. We discussed how to release the information raised during the summit to key stakeholders including athletes, parents, coaches and healthcare providers. We identified future areas for research and collaboration to enhance the health and safety of soccer (football) players.

The role of cervical muscles in mitigating concussion

OBJECTIVES

Increased neck strength has been hypothesized to lower sports related concussion risk, but lacks experimental evidence. The goal is to investigate the role cervical muscle strength plays in blunt impact head kinematics and the biofidelity of common experimental neck conditions. We hypothesize head kinematics do not vary with neck activation due to low short term human head-to-neck coupling; because of the lack of coupling, free-head experimental conditions have higher biofidelity than Hybrid III necks.

METHODS

Impacts were modeled using the Duke University Head and Neck Model. Four impact types were simulated with six neck conditions at eight impact positions. Peak resultant linear acceleration, peak resultant angular acceleration, Head Injury Criterion, and Head Impact Power compared concussion risk. To determine significance, maximum metric difference between activation states were compared to critical effect sizes (literature derived differences between mild and severe impact metrics).

RESULTS

Maximum differences between activation conditions did not exceed critical effect sizes. Kinematic differences from impact location and strength can be ten times cervical muscle activation differences. Hybrid III and free-head linear acceleration metrics were 6±1.0% lower and 12±1.5% higher than relaxed condition respectively. Hybrid III and free-head angular acceleration metrics were 12±4.0% higher and 2±2.7% lower than relaxed condition respectively.

CONCLUSIONS

Results from a validated neck model suggest increased cervical muscle force does not influence short term (<50ms) head kinematics in four athletically relevant scenarios. Impact location and magnitude influence head kinematics more than cervical muscle state. Biofidelic limitations of both Hybrid III and free-head experimental conditions must be considered.

Proceedings from the Ice Hockey Summit III: Action on Concussion

The Ice Hockey Summit III provided updated scientific evidence on concussions in hockey to inform these five objectives: 1) describe sport-related concussion (SRC) epidemiology, 2) classify prevention strategies, 3) define objective, diagnostic tests, 4) identify treatment, and 5) integrate science and clinical care into prioritized action plans and policy. Our action plan evolved from 40 scientific presentations. The 155 attendees (physicians, athletic trainers, physical therapists, nurses, neuropsychologists, scientists, engineers, coaches, and officials) voted to prioritize these action items in the final Summit session. 1) Establish a national and international hockey data base for SRC at all levels, 2) eliminate body checking in Bantam youth hockey games, 3) expand a behavior modification program (Fair Play) to all youth hockey levels, 4) enforce game ejection penalties for fighting in Junior A and professional hockey leagues, 5) establish objective tests to diagnose concussion at point of care (POC), and 6) mandate baseline testing to improve concussion diagnosis for all age groups. Expedient implementation of the Summit III prioritized action items is necessary to reduce the risk, severity, and consequences of concussion in the sport of ice hockey.

A Comparison of Various Cervical Muscle Strength Testing Methods Using a Handheld Dynamometer

BACKGROUND:

Cervical muscle strength, proposed as a modifiable risk factor in concussions, can be assessed using various methods. The purpose of this study was to compare the reliability and force outputs of 3 methods that use handheld dynamometry (HHD) for assessing cervical muscle strength.

HYPOTHESIS:

All 3 testing methods are reliable, and force outputs are significantly different between methods.

STUDY DESIGN:

Repeated-measures reliability.

LEVEL OF EVIDENCE:

Level 5.

METHODS:

The study used a convenience sample of 30 participants. HHD "make tests" for cervical extension, flexion, and right and left side bending were performed using lying push tests, sitting push tests, and sitting pull tests. A sole examiner performed all tests. Two testing sessions were conducted 1 week apart. Analysis included intraclass correlation coefficients (ICCs), repeated-measures analyses of variance (α = 0.05) with post hoc Bonferroni tests, and minimal detectable change (MDC) calculations.

RESULTS:

All testing methods were reliable; the lying push test had the greatest point estimate values (ICC, 0.89-0.95). Significant differences in force were found between the 3 testing methods. The MDC was most sensitive for the lying push method.

CONCLUSION:

Of the 3 cervical muscle testing methods investigated, the lying position with a push test had the largest ICC according to the point estimate and the most sensitive MDC. Force values between the 3 methods were significantly different, which suggests that consistent testing methods should be used.

CLINICAL RELEVANCE:

Results from this study support the clinical use of an HHD "make test" in a lying position for assessing cervical muscle strength. The test is reliable and more sensitive to change compared with tests in a seated position.

The effects of vision training, neck musculature strength, and reaction time on concussions in an athletic population

A concussion is a major concern across the athletic population. Prevention of concussions can lead to a decrease of 3.8 million concussions that occur annually in the United States. Vision training, increasing neck musculature strength and quick reaction times are thought to be ways to prevent concussions. The purpose of this study is to review the literature on vision training, neck musculature, and reaction time, and how these interventions can prevent concussions. Upon review of the literature, vision training is proven to prevent concussions in a collegiate football setting, but there is no literature on different levels or sports. There are inconclusive results on whether neck musculature strength prevents concussions. There are substantial results concluding reaction time does prevent concussions by allowing the athlete to protect and anticipate head impact lessening the severity of the blow to the head. More research needs to be done for all three interventions to prove across all ages and levels of every sport that vision training, neck musculature strength, and reaction time prevent concussions in an athletic population. If proven true, practitioners in an athletic setting can use vision training, increasing neck musculature strength, and increasing reaction time as interventions to help prevent concussions in an athletic population.

Comparison of Head Impact Exposure Between Male and Female High School Ice Hockey Athletes

BACKGROUND

Concussion incidence rates are higher among female than male athletes in sports played by both sexes. Biomechanical factors may play a role in observed sex-based differences in concussion incidence.

PURPOSE

To compare head impact counts and magnitudes during sports participation between male and female high school ice hockey athletes.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Over 2 seasons, a total of 21 male and 19 female ice hockey athletes from a single high school were instrumented with impact-sensing adhesive skin patches worn over the mastoid process while participating in games and practices. The impact sensors recorded the number, magnitude (peak linear acceleration [PLA, g] and peak angular acceleration [PAA, rad/s²] of the head; Head Impact Telemetry severity profile [HITsp]), and location of impacts sustained during each instrumented session. Head impact counts, magnitudes, and locations were compared between the sexes.

RESULTS

Males experienced more head impacts than females during games (mean ± SD: 7.7 ± 3.0 vs 5.3 ± 2.0, P < .001) as well as practices (4.3 ± 1.6 vs 3.8 ± 1.1, P = .002). Mean impact magnitudes were greater for females for PLA (18.8 g ± 1.7 g vs 17.1 g ± 1.6 g, P < .001) and HITsp (19.7 ± 1.5 vs 17.7 ± 1.4, P < .001), while mean PAA was greater for males (3057.6 ± 2.0 rad/s² vs 2778.3 ± 2.7 rad/s², P < .001). Female athletes experienced higher PLA, PAA, and HITsp magnitudes for the top 10%, 5%, and 1% of impacts (all P < .050). Males experienced more impacts to the front (34.3%) and back (31.7%) of the head, while females experienced more impacts to the side (43.1%) and top (4.1%) (χ² = 295.70, df = 3, P < .001).

CONCLUSION

While male high school ice hockey athletes experienced more head impacts than females, impact magnitudes tended to be higher for females.

Primary prevention of contact sports-related concussions in amateur athletes: a systematic review from the Eastern Association for the Surgery of Trauma

BACKGROUND

Awareness of the magnitude of contact sports-related concussions has risen exponentially in recent years. Our objective is to conduct a prospectively registered systematic review of the scientific evidence regarding interventions to prevent contact sports-related concussions.

METHODS

Using the Grading of Recommendations Assessment, Development, and Evaluation methodology, we performed a systematic review of the literature to answer seven population, intervention, comparator, and outcomes (PICO) questions regarding concussion education, head protective equipment, rules prohibiting high-risk activity and neck strengthening exercise for prevention of contact sports-related concussion in pediatric and adult amateur athletes. A query of MEDLINE, PubMed, Scopus, Cumulative Index of Nursing and Allied Health Literature, and Embase was performed. Letters to the editor, case reports, book chapters, and review articles were excluded, and all articles reviewed were written in English.

RESULTS

Thirty-one studies met the inclusion criteria and were applicable to our PICO questions. Conditional recommendations are made supporting preventive interventions concussion education and rules prohibiting high-risk activity for both pediatric and adult amateur athletes and neck strengthening exercise in adult amateur athletes. Strong recommendations are supported for head protective equipment in both pediatric and adult amateur athletes. Strong recommendations regarding newer football helmet technology in adult amateur athletes and rules governing the implementation of body-checking in youth ice hockey are supported.

CONCLUSION

Despite increasing scientific attention to sports-related concussion, studies evaluating preventive interventions remain relatively sparse. This systematic review serves as a call to focus research on primary prevention strategies for sports-related concussion.

LEVEL OF EVIDENCE

IV.

PROSPERO REGISTRATION NUMBER

#42016043019.

The Influence of Heavier Football Helmet Faceguards on Head Impact Location and Severity

OBJECTIVE

To determine whether players with heavier faceguards have increased odds of sustaining top of the head impacts and head impacts of higher severity.

DESIGN

Cohort study.

SETTING

On-field.

PARTICIPANTS

Thirty-five division I collegiate football players.

INTERVENTIONS

Faceguard mass was measured. Head impact location and severity (linear acceleration [gravity], rotational acceleration [radian per square second], and Head Impact Technology severity profile [unitless]) were captured for 19 379 total head impacts at practices using the Head Impact Telemetry System.

MAIN OUTCOME MEASURES

Players' faceguards were categorized as either heavier (>480 g) or lighter (≤480 g) using a median split. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed for sustaining top of the head impacts between faceguard groups using a random intercepts generalized logit model. We compared head impact severity between groups using random intercepts general linear models (α = 0.05). Player position was included in all models.

RESULTS

Overall, the 4 head impact locations were equally distributed across faceguard groups (F(3,26) = 2.16, P = 0.117). Football players with heavier faceguards sustained a higher proportion impacts to the top of the head (24.7% vs 17.5%) and had slightly increased odds of sustaining top (OR, 1.72; 95% CI, 1.01-2.94) head impacts rather than front of the head impacts.

CONCLUSIONS

Football players wearing heavier faceguards might be slightly more prone to sustaining a higher proportion of top of the head impacts, suggesting that greater faceguard mass may make players more likely to lower their head before collision. Individuals involved with equipment selection should consider the potential influence of faceguard design on head impact biomechanics when recommending the use of a heavier faceguard.

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.

Effect of neck flexor muscle activation on impact velocity of the head during backward falls in young adults

Falls are a common cause of traumatic brain injuries (TBI) across the lifespan. A proposed but untested hypothesis is that neck muscle activation influences impact severity and risk for TBI during a fall. We conducted backward falling experiments to test whether activation of the neck flexor muscles facilitates the avoidance of head impact, and reduces impact velocity if the head contacts the ground. Young adults (n=8) fell from standing onto a 30cm thick gymnastics mat while wearing a helmet. Participants were instructed to fall backward and (a) prevent their head from impacting the mat ("no head impact" trials); (b) allow their head to impact the mat, but with minimal impact severity ("soft impact" trials); and (c) allow their head to impact the mat, while inhibiting efforts to reduce impact severity ("hard impact" trials). Trial type associated with peak magnitude of electromyographic activity of the sternocleidomastoid (SCM) muscles (p<0.017), and with the vertical and horizontal velocity of the head at impact (p<0.001). Peak SCM activations, expressed as percent maximal voluntary isometric contraction (%MVIC), averaged 75.3, 67.5, and 44.5%MVIC in "no head impact", "soft impact", and "hard impact" trials, respectively. When compared to "soft impact" trials, vertical impact velocities in "hard impact" trials averaged 87% greater (3.23 versus 1.73m/s) and horizontal velocities averaged 83% greater (2.74 versus 1.50m/s). For every 10% increase in SCM %MVIC, vertical impact velocity decreased 0.24m/s and horizontal velocity decreased 0.22m/s. We conclude that SCM activation contributes to the prevention and modulation of head impact severity during backward falls.

Head and neck size and neck strength predict linear and rotational acceleration during purposeful soccer heading

There is increasing societal concern about the long-term effects of repeated impacts from soccer heading, but there is little information about ways to reduce head impact severity. The purpose of this study was to identify factors that contribute to head acceleration during soccer heading. One-hundred soccer players completed 12 controlled soccer headers. Peak linear (PLA) and rotational (PRA) accelerations were measured using a triaxial accelerometer and gyroscope. Head acceleration contributing factors were grouped into 3 categories: size (head mass, neck girth), strength (sternocleidomastoid, upper trapezius) and technique [kinematics (trunk, head-to-trunk range-of-motion), sternocleidomastoid and upper trapezius activity]. Multiple regression analyses indicated size variables explained 22.1% of the variance in PLA and 23.3% of the variance in PRA; strength variables explained 13.3% of the variance in PLA and 17.2% of the variance in PRA; technique variables did not significantly predict PLA or PRA. These findings suggest that head and neck size and neck strength predict PLA and PRA. Anthropometric and neck strength measurements should be considered when determining an athlete's readiness to begin soccer heading.