Peak Resultant Linear Acceleration Research Articles

Head Kinematics Associated with Off-Field Head Injury Assessment (HIA1) Events in a Season of English Elite-Level Club Men's and Women's Rugby Union Matches.

The purpose of this study was to investigate head kinematic variables in elite men's and women's rugby union and their ability to predict player removal for an off-field (HIA1) head injury assessment. Instrumented mouthguard (iMG) data were collected for 250 men and 132 women from 1865 and 807 player-matches, respectively, and synchronised to video-coded match footage. Head peak resultant linear acceleration (PLA), peak resultant angular acceleration (PAA) and peak change in angular velocity (dPAV) were extracted from each head acceleration event (HAE). HAEs were linked to documented HIA1 events, with ten logistical regression models for men and women, using a random subset of non-case HAEs, calculated to identify kinematic variables associated with HIA1 events. Receiver operating characteristic curves (ROC) were used to describe thresholds for HIA1 removal. Increases in PLA and dPAV were significantly associated with an increasing likelihood of HIA1 removal in the men's game, with an OR ranging from 1.05-1.12 and 1.13-1.18, respectively. The optimal values to maximise for both sensitivity and specificity for detecting an HIA1 were 1.96krad⋅s-2, 24.29 g and 14.75 rad⋅s-1 for PAA, PLA and dPAV, respectively. Only one model had any significant variable associated with increasing the likelihood of a HIA1 removal in the women's game-PAA with an OR of 8.51 (1.23-58.66). The optimal values for sensitivity and specificity for women were 2.01 krad⋅s-2, 25.98 g and 15.38rad⋅s-1 for PAA, PLA and dPAV, respectively. PLA and dPAV were predictive of men's HIA1 events. Further HIA1 data are needed to understand the role of head kinematic variables in the women's game. The calculated spectrum of sensitivity and specificity of iMG alerts for HIA1 removals in men and women present a starting point for further discussion about using iMGs as an additional trigger in the existing HIA process.

Does pad displacement correlate to impact severity metrics in football helmets?

As efforts to reduce sport-related head injuries continue, there is a need to better understand the mechanisms of an impact that influence the risk of sustaining a concussion. This study presents a method which can be used to separate football helmet pad displacement into normal and rotational components. Finite element models of three popular football helmets were used to simulate a variety of impacts per the National Football League (NFL) helmet testing protocol. Pad displacement components were evaluated for correlation with impact severity metrics including Head Injury Criterion (HIC), Diffuse Axonal Multi-Axis General Evaluation (DAMAGE), and Head Acceleration Response Metric (HARM). When combining all locations, displacement was not found to correlate well with severity metrics ( R2 < 0.44). However, trends did exist with normal displacement when evaluating data by impact location. Normal displacement was found to correlate strongly with HARM, HIC, and Peak Resultant Linear Acceleration (PRLA) at the side upper (SU) location ( R2 = 0.79–0.8). Overall, it was observed that helmets which maximize normal displacement without bottoming out performed better. Tangential displacement was not found to correlate well with any impact severity metrics even when evaluated by location. This study has provided a method to evaluate components of helmet pad normal displacement during simulations which may help guide design and optimization efforts for helmets under impact in critical locations.

Player and match characteristics associated with head acceleration events in elite-level men’s and women’s rugby union matches

ObjectiveTo examine the likelihood of head acceleration events (HAEs) as a function of previously identified risk factors: match time, player status (starter or substitute) and pitch location in elite-level men’s...

On-Field Evaluation of Mouthpiece-and-Helmet-Mounted Sensor Data from Head Kinematics in Football

PurposeWearable sensors are used to measure head impact exposure in sports. The Head Impact Telemetry (HIT) System is a helmet-mounted system that has been commonly utilized to measure head impacts in American football. Advancements in sensor technology have fueled the development of alternative sensor methods such as instrumented mouthguards. The objective of this study was to compare peak magnitude measured from high school football athletes dually instrumented with the HIT System and a mouthpiece-based sensor system.MethodsData was collected at all contact practices and competitions over a single season of spring football. Recorded events were observed and identified on video and paired using event timestamps. Paired events were further stratified by removing mouthpiece events with peak resultant linear acceleration below 10 g and events with contact to the facemask or body of athletes.ResultsA total of 133 paired events were analyzed in the results. There was a median difference (mouthpiece subtracted from HIT System) in peak resultant linear and rotational acceleration for concurrently measured events of 7.3 g and 189 rad/s2. Greater magnitude events resulted in larger kinematic differences between sensors and a Bland Altman analysis found a mean bias of 8.8 g and 104 rad/s2, respectively.ConclusionIf the mouthpiece-based sensor is considered close to truth, the results of this study are consistent with previous HIT System validation studies indicating low error on average but high scatter across individual events. Future researchers should be mindful of sensor limitations when comparing results collected using varying sensor technologies.

The Incidence and Propensity of Head Acceleration Events in a Season of Men’s and Women’s English Elite-Level Club Rugby Union Matches

ObjectivesTo describe and compare the incidence and propensity of head acceleration events (HAEs) using instrumented mouthguards (iMG) by playing position in a season of English elite-level men’s and women’s rugby union matches.MethodsiMG data were collected for 255 men and 133 women from 1,865 and 807 player-matches, respectively, and synchronised to video-coded match footage. Head peak resultant linear acceleration (PLA) and peak resultant angular acceleration (PAA) were extracted from each HAE. Mean incidence and propensity values were calculated across different recording thresholds for forwards and backs in addition to positional groups (front row, second row, back row, half backs, centres, back three) with 95% confidence intervals (CI) estimated. Significance was determined based on 95% CI not overlapping across recording thresholds.ResultsFor both men and women, HAE incidence was twice as high for forwards than backs across the majority of recording thresholds. HAE incidence and propensity were significantly lower in the women’s game compared to the men’s game. Back-row and front-row players had the highest incidence across all HAE thresholds for men’s forwards, while women’s forward positional groups and men’s and women’s back positional groups were similar. Tackles and carries exhibited a greater propensity to result in HAE for forward positional groups and the back three in the men’s game, and back row in the women’s game.ConclusionThese data offer valuable benchmark and comparative data for future research, HAE mitigation strategies, and management of HAE exposure in elite rugby players. Positional-specific differences in HAE incidence and propensity should be considered in future mitigation strategies.

Choosing Optimal Cutoff Frequencies for Filtering Linear Acceleration and Angular Velocity Signals Associated with Head Impacts Measured by Instrumented Mouthguards

Head impact sensors worn in the mouth are popular because they couple directly to the teeth and provide six-degree-of-freedom head measurements. Mouthpiece signal filters have conventionally used cutoff frequencies lower than recommended practices (Society of Automotive Engineers, SAE J211-1) to eliminate extraneous noise when measuring with live subjects. However, there is little information about the effects of filter choice on the accuracy of signals measured by instrumented mouthpieces. Lack of standardization in head impact measurement device post-processing techniques can result in data that are not comparable across studies or device brands. This study sought optimal filter cutoff frequencies for six-degree-of-freedom measurements made at the teeth using instrumented mouthguards. We collected linear acceleration and angular velocity signals at the head center of gravity (CG) using laboratory-grade instrumentation. We also collected and filtered similar six-degree-of-freedom measurements from an instrumented mouthguard using 24 cutoff frequencies, from 25 to 600 Hz. We transformed the measurements to linear acceleration at the center of gravity of the head (CG) using all kinematic variables at the teeth, optimizing linear and angular mouthguard cutoff frequencies with one equation. We calculated the percent error in transformed peak resultant linear acceleration and minimized the mean and standard deviation in error. The optimal cutoff frequencies were 175 Hz for linear acceleration and 250 Hz for angular velocity. Rigid impacts (3–5 ms duration) had higher optimal cutoff frequencies (175 Hz linear acceleration, 275 Hz angular velocity) than padded impacts (10–12 ms duration; 100 Hz linear acceleration, 175 Hz angular velocity), and all impacts together (3–12 ms duration; 175 Hz linear acceleration, 250 Hz angular velocity). Instrumented mouthpiece manufacturers and researchers using these devices should consider these optimal filter cutoff frequencies to minimize measurement error. Sport-specific filter criteria for teeth-based sensors may be warranted to account for the difference in optimal cutoff frequency combination by impact duration.

Investigating the influence of head kinematics on head injury metrics and factors to consider for football helmet design

There is a need to understand the relationship between head kinematics, impact severity metrics, and overall helmet performance as sports-related concussions continue to be prevalent. This study evaluates these relationships, emphasizing newly developed severity metrics that consider both translational and rotational contributions. Impact tests were performed following the NFL testing protocol on four prominent football helmets. The resulting data was used to determine Head Acceleration Response Metric (HARM), Diffuse Axonal Multi-Axis General Evaluation (DAMAGE), and Head Injury Criterion (HIC). HARM scores, a combination of HIC and DAMAGE, were ultimately used to solve for a Helmet Performance Score. When analyzing all impacts, DAMAGE showed a stronger correlation to HARM than HIC ( R2 = 0.76 vs R2 = 0.57); however, the strongest correlation existed between peak resultant angular velocity (PRAV) and HARM ( R2 = 0.87). When examining impacts at only the side, side upper (SU), and oblique front (OF) locations grouped together, HIC demonstrated the strongest correlation to HARM in the study ( R2 = 0.96). PRAV was the best predictor for HARM over peak resultant linear acceleration (PRLA) and peak resultant angular acceleration for four of the six impact locations (C, D, FMCO, and FMS) when analyzing the sites individually. The remaining locations (SU and OF) best predicted HARM using PRLA. These results are presented and discussed to aid in the research, design, and development of football helmets.

Driver head kinematics in grassroots dirt track racing crashes: A pilot analysis

Motorsport athletes experience head acceleration loading during crashes; however, there is limited literature quantifying the frequency and magnitude of these loads, particularly at the grassroots level of the sport. Understanding head motion experienced during crash events in motorsport is necessary to inform interventions to improve driver safety. This study aimed to quantify and characterize driver head and vehicle kinematics during crashes in open-wheel grassroots dirt track racing. Seven drivers (ages 16–22, n = 2 female) competing in a national midget car series were enrolled in this study over two racing seasons and were instrumented with custom mouthpiece sensors. Drivers’ vehicles were outfitted with an incident data recorder (IDR) to measure vehicle acceleration. Forty-one crash events were verified and segmented into 139 individual contact scenarios via film review. Peak resultant linear acceleration (PLA) of the vehicle and PLA, peak rotational acceleration (PRA), and peak rotational velocity (PRV) of the head were quantified and compared across the part of the vehicle contacted (i.e., tires or chassis), the vehicle location contacted (e.g., front, left, bottom), the external object contacted (i.e., another vehicle, wall, or the track), and the principal direction of force (PDOF). The median (95th percentile) PLA, PRA, and PRV of the head and PLA of the vehicle were 12.3 (37.3) g, 626 (1799) rad/s2, 8.92 (18.6) rad/s, and 23.2 (88.1) g, respectively. Contacts with a non-horizontal PDOF (n = 98, 71%) and contact with the track (n = 96, 70%) were common in the data set. Contact to the left side of the vehicle, with the track, and with a non-horizontal PDOF tended to have the greatest head kinematics compared to other factors in each sub-analysis. Results from this pilot study can inform larger studies of head acceleration exposure during crashes in the grassroots motorsports environment and may ultimately support evidence-based driver safety interventions.

Neurophysiological Effects of Repeated Soccer Heading in Youth.

Repeated head loading in sports is associated with negative long-term brain health, and there is growing evidence of short-term neurophysiological changes after repeated soccer heading. The objective of this study was to quantify the head kinematics and effects of repetitive soccer headers in adolescents using an instrumented mouthguard. Adolescent soccer players aged 13-18 years were randomly assigned to a kicking control, frontal heading, or oblique heading group. Participants completed neurophysiological assessments at three-time points: immediately prior to, immediately after, and approximately 24 h after completing 10 headers or kicks. The suite of assessments included the Post-Concussion Symptom Inventory, visio-vestibular exam, King-Devick test, modified Clinical Test of Sensory Interaction and Balance with force plate sway measurement, pupillary light reflex, and visual evoked potential. Data were collected for 19 participants (17 male). Frontal headers resulted in significantly higher peak resultant linear acceleration (17.4 ± 0.5 g) compared to oblique headers (12.1 ± 0.4 g, p < 0.001), and oblique headers resulted in significantly higher peak resultant angular acceleration (frontal: 1147 ± 45 rad/s2, oblique: 1410 ± 65 rad/s2, p < 0.001). There were no neurophysiological deficits for either heading group or significant differences from controls at either post-heading timepoint, and therefore, a bout of repeated headers did not result in changes in the neurophysiological measures evaluated in this study. The current study provided data regarding the direction of headers with the goal to reduce the risk of repetitive head loading for adolescent athletes.

Characterizing Exposure to Head Acceleration Events in Youth Football Using an Instrumented Mouthpiece.

Understanding characteristics of head acceleration events (HAEs) in youth football is vital in developing strategies to improve athlete safety. This study aimed to characterize HAEs in youth football using an instrumented mouthpiece. Youth football athletes (ages 11-13) participating on two teams were enrolled in this study for one season. Each athlete was instrumented with a mouthpiece-based sensor throughout the season. HAEs were verified on film to ensure that mouthpiece-based sensors triggered during contact. The number of HAEs, peak resultant linear and rotational accelerations, and peak resultant rotational velocity were quantified. Mixed effects models were used to evaluate differences in mean kinematic metrics among all HAEs for session type, athlete position, and contact surface. A total of 5,292 HAEs were collected and evaluated from 30 athletes. The median (95th percentile) peak resultant linear acceleration, rotational acceleration, and rotational velocity was 9.5g (27.0g), 666.4rads-2 (1863.3rads-2), and 8.5rads-1 (17.4rads-1), respectively. Athletes experienced six (22) HAEs per athlete per session (i.e., practice, game). Competition had a significantly higher mean number of HAEs per athlete per session and mean peak rotational acceleration. Peak resultant rotational kinematics varied significantly among athlete positions. Direct head impacts had higher mean kinematics compared to indirect HAEs, from body collisions. The results of this study demonstrate that session type, athlete position, and contact surface (i.e., direct, indirect) may influence HAE exposure in youth football.

Head Kinematics in Youth Ice Hockey by Player Speed and Impact Direction

Hockey is a fast-paced sport known for body checking, or intentional collisions used to separate opponents from the puck. Exposure to these impacts is concerning, as evidence suggests head impact exposure (HIE), even if noninjurious, can cause long-term brain changes. Currently, there is limited understanding of the effect of impact direction and collision speed on HIE. Video analysis was used to determine speed and direction for 162 collisions from 13 youth athletes. These data were paired with head kinematic data collected with an instrumented mouthpiece. Relationships between peak resultant head kinematics and speeds were evaluated with linear regression. Mean athlete speeds and relative velocity between athletes ranged from 2.05 to 2.76m/s. Mean peak resultant linear acceleration, rotational velocity, and rotational acceleration were 13.1g, 10.5rad/s, and 1112rad/s2, respectively. Significant relationships between speeds and head kinematics emerged when stratified by contact characteristics. HIE also varied by direction of collision; most collisions occurred in the forward-oblique (ie,offset from center) direction; frontal collisions had the greatest magnitude peak kinematics. These findings indicate that HIE in youth hockey is influenced by speed and direction of impact. This study may inform future strategies to reduce the severity of HIE in hockey.

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

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. Examine neck training effects with minimal equipment on neck strength and head kinematics following chest perturbations in youth athletes. Single-group, pretest-posttest case series. Athlete training center. Twenty-five (14 men and 11 women) youth soccer athletes (9.8 [1.5]y). Sixteen weeks of twice-weekly neck-focused resistance training utilizing bands, body weight, and manual resistance. 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. Neck extension (increase in median values for all: +4.5kg, +100%, P < .001; females: +4.5kg, +100%, P = .002; males: +2.2kg, +36%, P = .003) and flexion (all: +3.6kg, +114%, P < .001; females: +3.6kg, +114%, P = .004; males: +3.6kg, +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. 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.

Characterization of head impact exposure in boys’ youth ice hockey

ABSTRACT Ice hockey has one of the highest concussion rates among youth sports. Sensor technology has been implemented in contact and collision sports to inform the frequency and severity of head impacts experienced on-ice. However, existing studies have utilized helmet-mounted sensors with limited accuracy. The objective of this study was to characterize head kinematics of contact events in a sample of youth boys’ hockey players using a validated instrumented mouthpiece with improved accuracy. Head kinematics from 892 video-verified events were recorded from 18 athletes across 127 sessions. Median peak resultant linear acceleration, rotational velocity, and rotational acceleration of video-verified events were 7.4 g, 7.7 rad/s, and 576 rad/s2, respectively. Contact events occurred at a higher rate in games (2.48 per game) than practices (1.30 per practice). Scenarios involving head contact had higher peak kinematics than those without head contact. This study improves our understanding of head kinematics in boys’ youth hockey.

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 3.7kg padded impactor at 2m/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 ± 1.8g) and angular velocity (7.3 ± 0.5rad/s). Compared to the passive activation, increasing muscle activation decreased both peak resultant linear acceleration and angular velocity in the co-contracted (12.1 ± 1.5g, 6.8 ± 0.7rad/s) case and significantly decreased in the unilateral contraction (10.7 ± 1.7g, 6.5 ± 0.7rad/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.

An envelope of linear and rotational head motion during everyday activities

Various studies have characterized head kinematics in specific everyday activities by looking at linear and/or rotational acceleration characteristics, but each has evaluated a limited number of activities. Furthermore, these studies often present dissimilar and sometimes incomplete descriptions of the resulting kinematics, so the characteristics of normal everyday activities as a whole are not easily collectively summarized. The purpose of this study was to evaluate the literature investigating head kinematics associated with everyday activities and to generate a comprehensive kinematic boundary envelope describing these motions. The envelope constructed constitutes the current state of published knowledge regarding 'normally occurring' head accelerations. The envelope of kinematics represents activities commonly encountered and posing zero to minimal risk of injury to healthy individuals. Several kinematic measures, including linear accelerations, rotational velocities, and rotational accelerations, one may encounter as a result of normal everyday activities are summarized. A total of 11 studies encompassing 49 unique activities were evaluated. Examples of activities include sitting in a chair, jumping off a step, running, and walking. The peak resultant linear accelerations of the head reported in the literature were all less than 15g, while the peak resultant rotational accelerations and rotational velocities approach 1375rad/s2 and 12.8rad/s, respectively. The resulting design envelope can be used to understand the range of acceleration magnitudes a typical active person can expect to experience. The results are also useful to compare to other activities exposing the head to motion or impact including sports, military, automotive, aerospace and other sub-injurious and injurious events.

Differences in head accelerations and physiological demand between live and simulated professional horse racing

The purpose of this study was to determine if there are differences in mechanical and physiological demand between live and simulated racing. Fifteen male professional jockeys (31.8±9.5 years, 160.78±7.62 cm, 51.2±1.5 kg) were instrumented with inertial measurement units (IMUs) placed on their helmets to measure mechanical stress and a heart rate (HR) monitor. Head accelerations and HR were measured during a live race (between 5.5 and 6.5 furlongs) and a simulated race (equivalent of 6.5 furlongs or 1.5 min) on a race horse simulator. Paired t-tests were used to determine if there were differences between the two racing conditions for each dependent variable. Alpha level was set at P&lt;0.05. Average HR and peak HR were significantly higher during live than simulated racing. The peak resultant linear acceleration, the average resultant linear acceleration, and the peak resultant rotational velocity were significantly higher in live racing than simulated racing. There were no significant differences in average resultant rotational velocity. Simulated racing trials had consistently lower values of head accelerations compared to live racing trials. These results may provide justification for the use of a race horse simulator as a tool capable of use in rehabilitating and returning jockeys to ride following injury as the accelerations and velocities measured on simulated racing trials were lower, suggesting a safer sports-specific exercise, while still approaching the physiological demands of live racing.

Relative Motion Between the Helmet and the Head in Football Impact Test.

Approximately 1.6-3.8 million sports-related traumatic brain injuries occur each year in the U.S. Researchers track the head motion using a variety of techniques to study the head injury biomechanics. To understand how helmets provide head protection, quantification of the relative motion between the head and the helmet is necessary. The purpose of this study was to compare helmet and head kinematics and quantify the relative motion of helmet with respect to head during experimental representations of on-field American football impact scenarios. Seven helmet-to-helmet impact configurations were simulated by propelling helmeted crash test dummies into each other. Head and helmet kinematics were measured with instrumentation and an optical motion capture system. The analysis of results, from 10 ms prior to the helmet contact to 20 ms after the loss of helmet contact, showed that the helmets translated 12-41 mm and rotated up to 37 deg with respect to the head. The peak resultant linear acceleration of the helmet was about 2-5 times higher than the head. The peak resultant angular velocity of the helmet ranged from 37% less to 71% more than the head, depending on the impact conditions. The results of this study demonstrate that the kinematics of the head and the helmet are noticeably different and that the helmet rotates significantly with respect to the head during impacts. Therefore, capturing the helmet kinematics using a video motion tracking methodology is not sufficient to study the biomechanics of the head. Head motion must be measured independently of the helmet.

The role of cervical muscles in mitigating concussion

ObjectivesIncreased 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. MethodsImpacts 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). ResultsMaximum 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. ConclusionsResults 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.

Event-specific impact test protocol for ice hockey goaltender masks

ABSTRACT Goaltenders in the sport of ice hockey are at high risk for concussions from falls to the ice, player collisions and puck impacts. However, current methods used to certify helmets only consider head accelerations for drop tests which may not describe all common injury mechanisms relating to concussion. The purpose of this study was to describe the characteristics of 3 events associated with concussions for ice hockey goaltenders. A helmeted medium National Operating Committee on Standards for Athletic Equipment (NOCSAE) headform was impacted under conditions representing 3 injury events. Three impact locations’ velocities were selected for each event based on video analysis of real-world concussive events. Peak resultant linear acceleration, rotational acceleration and rotational velocity of the headform were measured. The University College Dublin Brain Trauma Model (UCDBTM) was used to calculate maximum principal strain (MPS) and von Mises stress in the cerebrum. Each impact event produced a unique dynamic response and brain stress and strain values. This demonstrates that a single impact event (i.e. falls) cannot adequately describe all impact events. As a result, impact protocols which assess multiple impact events such as the protocol described in this study should be used to evaluate ice hockey goaltender masks.

Head impact exposure from match participation in women’s rugby league over one season of domestic competition

ObjectivesTo quantify the magnitude, frequency, duration and distribution of head impact exposure in a women’s rugby league competition. DesignProspective cohort study. MethodsTwenty-one players had a wireless impact measuring device (X2Biosystems XPatch) behind their right ear during match participation. Head impact data were collected and downloaded for analysis. Median peak linear and rotational accelerations and impact locations between player positions were assessed using a Friedman repeated measures ANOVA on ranks with a Wilcoxon signed-rank test for post hoc analysis with a Bonferroni correction. ResultsA total of 1659 impacts to the head >10g were recorded (range 10g–91g) over the nine competition matches. There was a mean of 184±18 impacts per-match resulting in a mean of 14±12 impacts per-player per-match. The No. 8 prop recorded a mean of 29±27 impacts per-match, the No. 12 second-row forward recorded the highest median peak resultant linear acceleration (16g) per-match and the No. 11 second-row forward recorded the highest median peak resultant rotational acceleration (3696rad/s2). ConclusionsOur cohort of 21 female rugby league athletes were exposed to repetitive sub-concussive head impact exposure with an average of 14 impacts per-player per-match. Forwards were exposed to more impacts per-match than backs and these impacts were of higher magnitude. Most impacts occurred on the side of the head and were sustained during the second half of the game. Clinicians, coaches and players should be aware of the rates and magnitude of head impacts in female rugby league athletes.