Bodychecking Rules and Concussion in Elite Hockey

Athletes participating in contact sports such as ice hockey are exposed to a high risk of suffering a concussion. We determined whether recent rule changes regulating contact to the head introduced in 2010–11 and 2011–12 have been effective in reducing the incidence of concussion in the National Hockey League (NHL). A league with a longstanding ban on hits contacting the head, the Ontario Hockey League (OHL), was also studied. A retrospective study of NHL and OHL games for the 2009–10 to 2011–12 seasons was performed using official game records and team injury reports in addition to other media sources. Concussion incidence over the 3 seasons analyzed was 5.23 per 100 NHL regular season games and 5.05 per 100 OHL regular season games (IRR 1.04; 95% CI 1.01, 1.50). When injuries described as concussion-like or suspicious of concussion were included, incidences rose to 8.8 and 7.1 per 100 games respectively (IRR 1.23; 95% CI 0.81, 1.32). The number of NHL concussions or suspected concussions was lower in 2009–10 than in 2010–11 (IRR 0.61; 95% CI 0.45, 0.83), but did not increase from 2010–11 to 2011–12 (IRR 1.05; 95% CI 0.80, 1.38). 64.2% of NHL concussions were caused by bodychecking, and only 28.4% of concussions and 36.8% of suspected concussions were caused by illegal incidents. We conclude that rules regulating bodychecking to the head did not reduce the number of players suffering concussions during NHL regular season play and that further changes or stricter enforcement of existing rules may be required to minimize the risk of players suffering these injuries.     

A comparison of the magnitude and duration of linear and rotational head accelerations generated during hand-, elbow- and shoulder-to-head checks delivered by hockey players

Ice hockey has the highest rates for concussion among team sports in Canada. In elite play, the most common mechanism is impact to the head by an opposing player’s upper limb, with shoulder-to-head impacts accounting for twice as many concussions as elbow- and hand-to-head impacts combined. Improved understanding of the biomechanics of head impacts in hockey may inform approaches to prevention. In this study, we measured the magnitude and duration of linear and rotational head accelerations when hockey players (n = 11; aged 21–25) delivered checks “as hard as comfortable” to the head of an instrumented dummy with their shoulder, elbow and hand. There were differences in both peak magnitude and duration of head accelerations across upper limb impact sites, based on repeated-measures ANOVA (p < 0.005). Peak linear head accelerations averaged 1.9-fold greater for hand and 1.3-fold greater for elbow than shoulder (mean values = 20.35, 14.23 and 10.55 g, respectively). Furthermore, peak rotational head accelerations averaged 2.1-fold greater for hand and 1.8-fold greater for elbow than shoulder (1097.9, 944.1 and 523.1 rad/s², respectively). However, times to peak linear head acceleration (a measure of the duration of the acceleration impulse) were 2.1-fold longer for shoulder than elbow, and 2.5-fold longer for shoulder than hand (12.26, 5.94 and 4.98 ms, respectively), and there were similar trends in the durations of rotational head acceleration. Our results show that, in body checks to the head delivered by varsity-level hockey players, shoulder-to-head impacts generated longer durations but lower magnitude of peak head acceleration than elbow- and hand-to-head impacts.     

Risk of injury associated with bodychecking experience among youth hockey players

Background:

In a previous prospective study, the risk of concussion and all injury was more than threefold higher among Pee Wee ice hockey players (ages 11–12 years) in a league that allows bodychecking than among those in a league that does not. We examined whether two years of bodychecking experience in Pee Wee influenced the risk of concussion and other injury among players in a Bantam league (ages 13–14) compared with Bantam players introduced to bodychecking for the first time at age 13.

Methods:

We conducted a prospective cohort study involving hockey players aged 13–14 years in the top 30% of divisions of play in their leagues. Sixty-eight teams from the province of Alberta (n = 995), whose players had two years of bodychecking experience in Pee Wee, and 62 teams from the province of Quebec (n = 976), whose players had no bodychecking experience in Pee Wee, participated. We estimated incidence rate ratios (IRRs) for injury and for concussion.

Results:

There were 272 injuries (51 concussions) among the Bantam hockey players who had bodychecking experience in Pee Wee and 244 injuries (49 concussions) among those without such experience. The adjusted IRRs for game-related injuries and concussion overall between players with bodychecking experience in Pee Wee and those without it were as follows: injury overall 0.85 (95% confidence interval [CI] 0.63 to 1.16); concussion overall 0.84 (95% CI 0.48 to 1.48); and injury resulting in more than seven days of time loss (i.e., time between injury and return to play) 0.67 (95% CI 0.46 to 0.99). The unadjusted IRR for concussion resulting in more than 10 days of time loss was 0.60 (95% CI 0.26 to 1.41).

Interpretation:

The risk of injury resulting in more than seven days of time loss from play was reduced by 33% among Bantam hockey players in a league where bodychecking was allowed two years earlier in Pee Wee compared with Bantam players introduced to bodychecking for the first time at age 13. In light of the increased risk of concussion and other injury among Pee Wee players in a league where bodychecking is permitted, policy regarding the age at which hockey players are introduced to bodychecking requires further consideration.Rates of participation in youth-level ice hockey are high in North America.^1,2 There is growing concern regarding the impact of concussion in this population.^3–5 Body-checking is the reported mechanism for 45%–86% of injuries in youth ice hockey.^5–11 Internationally, the age group at which bodychecking is introduced varies. In Canada, bodychecking is introduced in Pee Wee leagues (ages 11–12 years), except in the province of Quebec, where it is introduced in Bantam (ages 13–14).¹²The age at which bodychecking should be introduced is controversial. We recently reported that the risk of injury and concussion in a Pee Wee league that allows bodychecking was more than threefold higher than in a Pee Wee league that does not allow bodychecking.⁹ Findings from systematic reviews support these findings.^13,14Injury rates may increase when players begin to learn bodychecking, because it is a new skill. If so, injury rates would be expected to be higher among players without bodychecking experience in Pee Wee (i.e., those in Quebec) than among players introduced to body-checking two years earlier in Pee Wee (e.g., in Alberta). We examined whether the risk of concussion and other injury among hockey players in Bantam leagues differed between players with and those without bodychecking experience in Pee Wee.     

Biomechanical correlates of symptomatic and asymptomatic neurophysiological impairment in high school football

Concussion is a growing public health issue in the United States, and chronic traumatic encephalopathy (CTE) is the chief long-term concern linked to repeated concussions. Recently, attention has shifted toward subconcussive blows and the role they may play in the development of CTE. We recruited a cohort of high school football players for two seasons of observation. Acceleration sensors were placed in the helmets, and all contact activity was monitored. Pre-season computer-based neuropsychological tests and functional magnetic resonance imaging (fMRI) tests were also obtained in order to assess cognitive and neurophysiological health. In-season follow-up scans were then obtained both from individuals who had sustained a clinically-diagnosed concussion and those who had not. These changes were then related through stepwise regression to history of blows recorded throughout the football season up to the date of the scan. In addition to those subjects who had sustained a concussion, a substantial portion of our cohort who did not sustain concussions showed significant neurophysiological changes. Stepwise regression indicated significant relationships between the number of blows sustained by a subject and the ensuing neurophysiological change. Our findings reinforce the hypothesis that the effects of repetitive blows to the head are cumulative and that repeated exposure to subconcussive blows is connected to pathologically altered neurophysiology.     

Consequences of Repeated Blood-Brain Barrier Disruption in Football Players

The acknowledgement of risks for traumatic brain injury in American football players has prompted studies for sideline concussion diagnosis and testing for neurological deficits. While concussions are recognized etiological factors for a spectrum of neurological sequelae, the consequences of sub-concussive events are unclear. We tested the hypothesis that blood-brain barrier disruption (BBBD) and the accompanying surge of the astrocytic protein S100B in blood may cause an immune response associated with production of auto-antibodies. We also wished to determine whether these events result in disrupted white matter on diffusion tensor imaging (DT) scans. Players from three college football teams were enrolled (total of 67 volunteers). None of the players experienced a concussion. Blood samples were collected before and after games (n = 57); the number of head hits in all players was monitored by movie review and post-game interviews. S100B serum levels and auto-antibodies against S100B were measured and correlated by direct and reverse immunoassays (n = 15 players; 5 games). A subset of players underwent DTI scans pre- and post-season and after a 6-month interval (n = 10). Cognitive and functional assessments were also performed. After a game, transient BBB damage measured by serum S100B was detected only in players experiencing the greatest number of sub-concussive head hits. Elevated levels of auto-antibodies against S100B were elevated only after repeated sub-concussive events characterized by BBBD. Serum levels of S100B auto-antibodies also predicted persistence of MRI-DTI abnormalities which in turn correlated with cognitive changes. Even in the absence of concussion, football players may experience repeated BBBD and serum surges of the potential auto-antigen S100B. The correlation of serum S100B, auto-antibodies and DTI changes support a link between repeated BBBD and future risk for cognitive changes.     

Disorders of the Menstrual Cycle in Elite Female Ice Hockey Players and Figure Skaters

The purpose of this study was to assess and compare the incidence of delayed menarche and menstrual dysfunction among elite ice hockey players and figure skaters. Forty-three ice hockey players (23.5 ± 4.8 years, 68.2 ± 1.2 kg, 1.68 ± 0.01 m) and 39 figure skaters (17.5 ± 3.4 years, 53.7 ± 5.8 kg, 1.64 ± 0.05 m) completed a self-administered questionnaire on their menstrual status and history, training regimens and lifestyle. Age at menarche did not differ significantly between ice hockey players (13.3 ± 1.3 years) and figure skaters (13.7 ± 1.4 years). Menarche was unrelated to nationality, vigorous training premenarche or age at which the athlete began her sport, but was correlated with the age at menarche of the athletes’ mothers (r = 0.39, p &lt; 0.05). Hormonal contraceptives were used by 35% of ice hockey players and 15% of the figure skaters. Amenorrhea and oligomenorrhea were experienced by 7.1% and 38.7% of postmenarcheal, ice hockey players and figure skaters respectively not using hormonal contraceptives. Menstrual dysfunction was associated with both age and age at menarche in the ice hockey players only. Training factors, and psychological pressure were perceived by the athletes to contribute to menstrual dysfunction. A greater training volume, younger age at commencing sport, lower body mass, greater subjective body image pressure and younger biological and gynaecological age were reported among the figure skaters, and were proposed to explain the higher incidence of menstrual dysfunction among the figure skaters compared with the ice hockey players. Figure skaters appear at increased risk of amenorrhea and oligomenorrhea compared with ice hockey players, which may be linked to training and physical characteristics of the sports.     

An algorithm for estimating acceleration magnitude and impact location using multiple nonorthogonal single-axis accelerometers

Accelerations of the head are the likely cause of concussion injury, but identifying the specific etiology of concussion has been difficult due to the lack of a valid animal or computer model. Contact sports, in which concussions are a rising health care concern, offer a unique research laboratory environment. However, measuring head acceleration in the field has many challenges including the need for large population sampling because of the relatively low incidence of concussions. We report a novel approach for calculating linear acceleration that can be incorporated into a head-mounted system for on-field use during contact sports. The advantages of this approach include the use of single-axis linear accelerometers, which reduce costs, and a nonorthogonal arrangement of the accelerometers, which simplifies the design criteria for a head-mounted and helmet compatible system. The purpose of this study was to describe the algorithm and evaluate its accuracy for measuring linear acceleration magnitude and impact location using computer simulation and experimental tests with various accelerometer configurations. A 10% error in magnitude and a 10 deg error in impact location were achieved using as few as six single-axis accelerometers mounted on a hemispherical headform.     

Myelin Water Fraction Is Transiently Reduced after a Single Mild Traumatic Brain Injury – A Prospective Cohort Study in Collegiate Hockey Players

Impact-related mild traumatic brain injuries (mTBI) are a major public health concern, and remain as one of the most poorly understood injuries in the field of neuroscience. Currently, the diagnosis and management of such injuries are based largely on patient-reported symptoms. An improved understanding of the underlying pathophysiology of mTBI is urgently needed in order to develop better diagnostic and management protocols. Specifically, dynamic post-injury changes to the myelin sheath in the human brain have not been examined, despite ‘compromised white matter integrity’ often being described as a consequence of mTBI. In this preliminary cohort study, myelin water imaging was used to prospectively evaluate changes in myelin water fraction, derived from the T2 decay signal, in two varsity hockey teams (45 players) over one season of athletic competition. 11 players sustained a concussion during competition, and were scanned at 72 hours, 2 weeks, and 2 months post-injury. Results demonstrated a reduction in myelin water fraction at 2 weeks post-injury in several brain areas relative to preseason scans, including the splenium of the corpus callosum, right posterior thalamic radiation, left superior corona radiata, left superior longitudinal fasciculus, and left posterior limb of the internal capsule. Myelin water fraction recovered to pre-season values by 2 months post-injury. These results may indicate transient myelin disruption following a single mTBI, with subsequent remyelination of affected neurons. Myelin disruption was not apparent in the athletes who did not experience a concussion, despite exposure to repetitive subconcussive trauma over a season of collegiate hockey. These findings may help to explain many of the metabolic and neurological deficits observed clinically following mTBI.     

TRAINING-INDUCED CHANGES IN DRAG-FLICK TECHNIQUE IN FEMALE FIELD HOCKEY PLAYERS

The penalty corner is one of the most important goal plays in field hockey. The drag-flick is used less by women than men in a penalty corner. The aim of this study was to describe training-induced changes in the drag-flick technique in female field hockey players. Four female players participated in the study. The VICON optoelectronic system (Oxford Metrics, Oxford, UK) measured the kinematic parameters of the drag-flick with six cameras sampling at 250 Hz, prior to and after training. Fifteen shots were captured for each subject. A Wilcoxon test assessed the differences between pre-training and post-training parameters. Two players received specific training twice a week for 8 weeks; the other two players did not train. The proposed drills improved the position of the stick at the beginning of the shot (p < 0.05), the total distance of the shot (p < 0.05) and the rotation radius at ball release (p < 0.01). It was noted that all players had lost speed of the previous run. Further studies should include a larger sample, in order to provide more information on field hockey performance.     

The influence of impact source on variables associated with strain for impacts in ice hockey

Concussion can occur from a variety of events (falls to ice, collisions etc) in ice hockey, and as a result it is important to identify how these different impact sources affect the relationship between impact kinematics and strain that has been found to be associated to this injury. The purpose of this research was to examine the relationship between kinematic variables and strain in the brain for impact sources that led to concussion in ice hockey. Video of professional ice hockey games was analyzed for impacts that resulted in reported clinically diagnosed concussions. The impacts were reconstructed using physical models/ATDs to determine the impact kinematics and then simulated using finite element modelling to determine maximum principal strain and cumulative strain damage measure. A stepwise linear regression was conducted between linear acceleration, change in linear velocity, rotational acceleration, rotational velocity, and strain response in the brain. The results for the entire dataset was that rotational acceleration had the highest r² value for MPS (r² = 0.581) and change in rotational velocity for cumulative strain damage measure (r² = 450). When the impact source (shoulder, elbow, boards, or ice impacts) was isolated the rotational velocity and acceleration r² value increased, indicating that when evaluating the relationships between kinematics and strain based metrics the characteristics of the impact is an important factor. These results suggest that rotational measures should be included in future standard methods and helmet innovation and design in ice hockey as they have the highest association with strain in the brain tissues.     

Field hockey players have different values of ulnar and tibial motor nerve conduction velocity than soccer and tennis players

The aim of this study was to describe motor nerve conduction velocity in upper and lower extremities in sportsmen. Fifteen high-level field hockey players, seventeen soccer players and ten tennis players were recruited from the Polish National Field Hockey League, Polish Soccer League Clubs, and Polish Tennis Association clubs,respectively. The control group comprised of seventeen healthy, non-active young men. Nerve conduction velocities of ulnar and tibial nerve were assessed with NeuroScreen electromyograph (Toennies, Germany) equipped with standard techniques of supramaximal percutaneus stimulation with constant current and surface electrodes. No significant differences in motor nerve conduction velocities were found between dominant and non-dominant limbs in each studied group. Ulnar nerve conduction velocity measured from above elbow to below elbow was significantly lower only in the field hockey players' dominant limb. Tibial conduction velocity of the field hockey players' non-dominant lower limb was higher in comparison to the tennis players and the control group. There was no significant correlation between body mass and NCV as well as between height of subjects and NCV in both athletes or non-athletes. A slight trend towards a lower TCV values in athletes with longer duration of practicing sport was found. It was most pronounced in the non-dominant lower extremity of field hockey players.     

Evaluation of jump protocols to assess leg power and predict hockey playing potential

The purposes of this study were (a) to determine the measurement device and jumping protocol most appropriate for testing the leg power of elite hockey players and (b) to assess the relationship of leg power measurements to hockey playing ability as indicated by draft selection order. Comparisons were made of leg power measurements from the top 95 players entering the National Hockey League Entry Draft using 2 devices (Vertec and Just Jump) and 2 jump protocols (countermovement and squat). Players' leg powers were ranked from highest to lowest power using each device and protocol and were correlated with draft selection order. Vertec leg power measurements were highest (5,511-5,631 W), but there were no significant differences in power between the 2 jumping protocols on either device. Vertec squat jump provided the highest correlation (0.47) between leg power ranking and selection order and was judged to most closely approximate the full-body coordinated movements involved in hockey. The Vertec device using a squat jump protocol is most appropriate for coaches and fitness specialists to use when evaluating hockey potential based on the off-ice leg power measurements of elite hockey players.     

Altered Blood Biomarker Profiles in Athletes with a History of Repetitive Head Impacts

The long-term health effects of concussion and sub-concussive impacts in sport are unknown. Growing evidence suggests both inflammation and neurodegeneration are pivotal to secondary injury processes and the etiology of neurodegenerative diseases. In the present study we characterized circulating brain injury and inflammatory mediators in healthy male and female athletes according to concussion history and collision sport participation. Eighty-seven university level athletes (male, n = 60; female, n = 27) were recruited before the start of the competitive season. Athletes were healthy at the time of the study (no medications, illness, concussion or musculoskeletal injuries). Dependent variables included 29 inflammatory and 10 neurological injury analytes assessed in the peripheral blood by immunoassay. Biomarkers were statistically evaluated using partial least squares multivariate analysis to identify possible relationships to self-reported previous concussion history, number of previous concussions and collision sport participation in male and female athletes. Multiple concussions were associated with increases in peripheral MCP-1 in females, and MCP-4 in males. Collision sport participation was associated with increases in tau levels in males. These results are consistent with previous experimental and clinical findings that suggest ongoing inflammatory and cerebral injury processes after repetitive mild head trauma. However, further validation is needed to correlate systemic biomarkers to repetitive brain impacts, as opposed to the extracranial effects common to an athletic population such as exercise and muscle damage.     

Finite element modelling of equestrian helmet impacts exposes the need to address rotational kinematics in future helmet designs

Jockey head injuries, especially concussions, are common in horse racing. Current helmets do help to reduce the severity and incidences of head injury, but the high concussion incidence rates suggest that there may be scope to improve the performance of equestrian helmets. Finite element simulations in ABAQUS/Explicit were used to model a realistic helmet model during standard helmeted rigid headform impacts and helmeted head model University College Dublin Brain Trauma Model (UCDBTM) impacts.

Current helmet standards for impact determine helmet performance based solely on linear acceleration. Brain injury-related values (stress and strain) from the UCDBTM showed that a performance improvement based on linear acceleration does not imply the same improvement in head injury-related brain tissue loads. It is recommended that angular kinematics be considered in future equestrian helmet standards, as angular acceleration was seen to correlate with stress and strain in the brain.     

Metabolomics profiling of concussion in adolescent male hockey players: a novel diagnostic method

Introduction

Concussions are a major health concern as they cause significant acute symptoms and in some athletes, long-term neurologic dysfunction. Diagnosis of concussion can be difficult, as are the decisions to stop play.

Objective

To determine if concussions in adolescent male hockey players could be diagnosed using plasma metabolomics profiling.

Methods

Plasma was obtained from 12 concussed and 17 non-concussed athletes, and assayed for 174 metabolites with proton nuclear magnetic resonance and direct injection liquid chromatography tandem mass spectrometry. Data were analysed with multivariate statistical analysis and machine learning.

Results

The estimated time from concussion occurrence to blood draw at the first clinic visit was 2.3 ± 0.7 days. Using principal component analysis, the leading 10 components, each containing 9 metabolites, were shown to account for 82 % of the variance between cohorts, and relied heavily on changes in glycerophospholipids. Cross-validation of the classifier using a leave-one out approach demonstrated a 92 % accuracy rate in diagnosing a concussion (P < 0.0001). The number of metabolites required to achieve the 92 % diagnostic accuracy was minimized from 174 to as few as 17 metabolites. Receiver operating characteristic analyses generated an area under the curve of 0.91, indicating excellent concussion diagnostic potential.

Conclusion

Metabolomics profiling, together with multivariate statistical analysis and machine learning, identified concussed athletes with >90 % certainty. Metabolomics profiling represents a novel diagnostic method for concussion, and may be amenable to point-of-care testing.

     

The biomechanics of concussion for ice hockey head impact events

The purpose of this research was to conduct reconstructions of concussive and non-concussive impacts in ice hockey to determine the biomechanics and thresholds of concussive injury in ice hockey. Videos of concussive and non-concussive impacts in an elite professional ice hockey league in North America were reconstructed using physical and finite element model methods. Eighty concussive and 45 non-concussive events were studied. Logistic regressions indicate significant thresholds for concussion for linear/rotational acceleration and CSDM_10%. Impacts in ice hockey were mostly long duration events, longer than 15?ms. These results have significant implications for helmet standards and development to prevent concussion.     

In your face: facial metrics predict aggressive behaviour in the laboratory and in varsity and professional hockey players

Facial characteristics are an important basis for judgements about gender, emotion, personality, motivational states and behavioural dispositions. Based on a recent finding of a sexual dimorphism in facial metrics that is independent of body size, we conducted three studies to examine the extent to which individual differences in the facial width-to-height ratio were associated with trait dominance (using a questionnaire) and aggression during a behavioural task and in a naturalistic setting (varsity and professional ice hockey). In study 1, men had a larger facial width-to-height ratio, higher scores of trait dominance, and were more reactively aggressive compared with women. Individual differences in the facial width-to-height ratio predicted reactive aggression in men, but not in women (predicted 15% of variance). In studies 2 (male varsity hockey players) and 3 (male professional hockey players), individual differences in the facial width-to-height ratio were positively related to aggressive behaviour as measured by the number of penalty minutes per game obtained over a season (predicted 29 and 9% of the variance, respectively). Together, these findings suggest that the sexually dimorphic facial width-to-height ratio may be an 'honest signal' of propensity for aggressive behaviour.