A comparison of sub-concussive impact attenuating capabilities of ice hockey helmets with and without XRD foam

Proper evaluation of ski helmet designs and safety standards should rely on head impact conditions involved in skiing and snowboarding head injuries. To study these impacts, main crash scenarios involving head injuries are numerically replicated. Multibody models of skiers and snowboarders were developed to investigate five common crash scenarios involved in traumatic brain injury: forward and sideways skiing falls, snowboarding backward falls, collisions between users and collisions with obstacles. For each scenario, the influence of crash conditions on head impact (location, speed, linear and rotational accelerations) and risk of injury are evaluated. Crash conditions were initial velocity, user height, position and approach angle, slope steepness, obstacles, and snow stiffness. One thousand one hundred forty-nine crashes were simulated and three significant levels of impact conditions were discriminated over the investigated crash scenarios: 1) the smallest normal-to-slope impact velocities (6 km·h; 22 km·h) and peak linear accelerations (42g; 75g) were obtained during forward and sideways skiing falls; 2) snowboarding backward falls and collisions between users were associated with high normal-to-surface impact velocities (26 km·h; 32 km·h) and head accelerations (80g; 149g) above one published threshold for mild traumatic brain injury but below the pass/fail criteria of helmet standard tests; 3) collisions with obstacles were associated with high normal-to-surface impact velocities (19 km·h; 35 km·h) and the highest head accelerations (626g; 1885g). Current impact conditions of helmet standard evaluations consistently replicate collisions with obstacles, but need to be revised to better reflect other significant crash scenarios leading to traumatic brain injury.

A pilot study was performed to measure head impact accelerations in collegiate men’s ice hockey during the 2005–2007 seasons using helmets instrumented with Head Impact Telemetry System technology to monitor and record linear head accelerations and impact locations in situ. The objectives of this study were (1) to quantify the relationship between resultant peak linear head acceleration and impact location for in situ head impacts in collegiate men’s ice hockey, (2) to quantify the frequency and severity of impacts to the facemask, and (3) to determine if in situ impacts occurred such that the peak resultant linear head acceleration was higher than the peak resultant linear headform acceleration from a 40-in. linear drop (as in ASTM F1045–99) on the same helmet at a similar impact location. Voluntary participants (n=5 and 7 for years 1 and 2, respectively) wore instrumented helmets which monitored head impact accelerations sustained by each player during all games and practices. Head impact data were grouped by impact location into five bins representing top, back, side, forehead, and facemask. Forehead impacts represented impacts to the helmet shell as distinguished from facemask impacts. Additionally, a sample instrumented helmet was impacted in the laboratory at forehead, side, rear, and top impact locations (40-in. drop, three trials per location, test setup as specified in ASTM F1045-99). The mean peak resultant linear headform acceleration for each impact location was determined for analysis. Of the 4,393 recorded head impacts, 33.2 % were to the back of the helmet. This percentage increased to 59.2 % for impacts above 70 g. Facemask impacts accounted for 12.2 % of all impacts but only 2.4 % of impacts above 70 g. Over two seasons, five in situ impacts occurred such that the peak resultant linear head acceleration was greater than the mean peak resultant linear headform acceleration for a corresponding impact location in the laboratory. This study found that the most common impact location in ice hockey, particularly for impacts with higher peak linear accelerations, was the back of the head and demonstrated that facemask impacts were typically of a lower magnitude. The five impacts or ∼0.4 per player/season that exceeded the peak linear acceleration associated with 40-in. laboratory drops suggested that the impact energy specified in ASTM F1045 may not reflect the highest energy impacts seen in situ.

The purpose of this study was to investigate if the impact attenuation properties of ice hockey helmets change after being used for one season in a professional ice hockey league. Eighteen helmets from a male team and 10 helmets from a female team were compared to 13 new helmets. Every helmet was impact tested three times for two impact locations, side and front. The median peak linear acceleration for all front impacts were significantly higher ( p < 0.05) for the helmets from the female team compared to the helmets from the male team. Compared to the new helmets, both men’s and women’s helmets had significantly lower median peak angular acceleration ( p < 0.01) and peak angular velocity ( p< 0.001). For side impacts, the women’s helmets had significantly higher peak linear acceleration compared to the men’s and new helmets ( p < 0.001). Both men’s and women’s helmets had significantly higher peak angular acceleration compared to the new helmets ( p < 0.001), and women’s helmets also had significantly higher peak angular acceleration compared to men’s helmets. Compared to men’s and new helmets, the results show that women’s helmets have worse impact attenuation properties after one season. However, all used helmets satisfied the passing threshold for test standards and the differences in calculated injury risk were small. This information may assist in establishing recommendations for the expected lifetime usage for ice hockey helmets and support manufacturers to develop safer ice hockey helmets.

This research was undertaken to examine a new method for assessing the performance of ice hockey helmets. It has been proposed that the current centric impact standards for ice hockey helmets, measuring peak linear acceleration, have effectively eliminated traumatic head injuries in the sport, but that angular acceleration and brain tissue deformation metrics are more sensitive to the conditions associated with concussive injuries, which continue to be a common injury. Ice hockey helmets were impacted using both centric and non-centric impact protocols at 7.5 m/s using a linear impactor. Dynamic impact responses and brain tissue deformations from the helmeted centric and non-centric head form impacts were assessed with respect to proposed concussive injury thresholds from the literature. The results of the helmet impacts showed that the method used was sensitive enough to distinguish differences in performance between helmet models. The results have shown that peak linear acceleration yielded low magnitudes of response to an impact, but peak angular acceleration and brain deformation metrics consistently reported higher magnitudes, reflecting a high risk for incurring a mild traumatic brain injury.

Although there are currently no standard tests measuring rotational head motion for ice hockey, researchers have proposed test methods which induce rotational head motion from an impact and may reflect more closely how concussions occur in the sport. Recently, Meehan et al. developed a test method for ice hockey helmets to represent concussive injuries associated with ice hockey. While that provided a method that used impact parameters closer to what may be experienced, the research did not evaluate if different helmets would produce differing results under those loading conditions. The purpose of this study is to use the methods developed by Meehan et al. to evaluate the protective capacity of three different ice hockey helmet designs. This research used monorail drop rig and pneumatic ram systems to follow the protocol of Meehan with a bare headform condition and three different helmet designs, allowing for differences in linear and rotational acceleration, rotational velocity, and maximum principal strain to be determined. The results of this research found that the test method developed by Meehan et al. does result in significant differences between different helmets and helmet designs under identical impact conditions. However, these differences were limited which may be a reflection of the test method as well as commonality in terms of how ice hockey helmets are designed; the different models may not be sufficiently different enough to provide different results under these loading conditions.

Ice hockey helmets are certified to standards that include drop tests that limit linear acceleration imparted to a surrogate headform. Historically, this test has been successful as a measure of a helmet's ability to absorb energy and mitigate serious to severe head injury. However, new interest in concussions has demanded new test methods to address these brain injuries. Evolving research shows the importance of rotational kinematics in concussion and hence the desire for a rotational helmet impact test. The standard drop test simulates hard, flat surfaces in hockey such as the ice, boards, and glass. However, open ice collisions involving shoulder and elbow impacts are poorly defined in terms of surface stiffness, impact speed, and responding head kinematics. In this present work, we explore the feasibility of measuring these factors directly in a series of on-ice experiments using a Hybrid III pedestrian crash test dummy setup to resemble a hockey player. The dummy head was instrumented for linear and rotational accelerations. A special test fixture simulated a realistic hockey posture and head elevation. Two experienced adult male hockey players delivered a series of increasingly aggressive shoulder and elbow strikes to the helmeted dummy head at elevated skating speeds. Results showed that elbow strike acceleration and time duration were similar to a standard drop test at a lower drop height. Shoulder impacts were of longer time duration and could be simulated by a padded strike face added to a linear impactor helmet test apparatus. The linear impactor was set up with the same Hybrid III head and helmet from the on-ice experiments. Iterative tests were run to converge on the design of a padded face to match the shoulder response from the on-ice tests. This pilot program was shown to be a feasible approach toward developing a shoulder impact simulator, although limitations are discussed. These on-ice head impact data provide insight into the unique character of shoulder-to-head and elbow-to-head impacts. This new test method may provide a foundation for future ice hockey test standards.

Player-to-player contact is the most frequent head impact mechanism in collegiate ice hockey. Training with three-dimensional multiple object tracking (3D-MOT) could potentially reduce the quantity and severity of head impacts by enhancing player anticipation of these impacts. PURPOSE: The purpose of this study was to utilize 3D-MOT training as a tool to reduce the quantity and severity of head impacts in NCAA Division III men’s and women’s ice hockey players. METHODS: Collegiate men’s and women’s ice hockey players (N = 33; men = 17, women = 16) were randomly assigned to a 3D-MOT group (3D-MOT = 17) or control group (C = 16). 3D-MOT training occurred twice per week for 12 weeks throughout one regular season. Quantity, location, linear acceleration, and rotational velocity of head impacts were measured in practices and games. Independent samples t-tests compared peak linear acceleration and peak rotational velocity between groups. Pearson chi square analysis compared the quantity of impacts between groups. Independent groups ANOVAs compared peak linear acceleration and peak rotational velocity of impacts between player positions and peak linear acceleration and peak rotational velocity at five different helmet locations between groups. RESULTS: 3D-MOT forwards sustained head impacts with greater mean peak linear acceleration (3D-MOT = 41.33 + 28.54g; C = 38.03 + 24.30g) and mean peak rotational velocity (3D-MOT = 13.59 + 8.18 rad.sec-1; C = 12.47 + 7.69 rad.sec-1) in games, and greater mean peak rotational velocity in practices versus control forwards (3D-MOT = 11.96 + 6.77 rad.sec-1; C = 10.22 + 6.95 rad.sec-1). Conversely, 3D-MOT defensemen sustained fewer in-game head impacts (3D-MOT = 181 head impacts; C = 282 head impacts) and head impacts with a mean peak rotational velocity less than control defensemen (3D-MOT = 11.54 + 6.76 rad.sec-1; C = 13.65 + 8.43 rad.sec-1). There was no significant difference for all other parameters analyzed between 3D-MOT and control groups. CONCLUSION: 3D-MOT training reduced the quantity and severity of head impacts for defensemen in games, but not for forwards. Player position may play an important role in future interventions to reduce quantity and severity of head impacts in collegiate ice hockey.

IntroductionWhile protective headwear products (PHP) are designed to protect older adults from fall-related head injuries, there are limited data on their protective capacity. This study’s goal was to assess the impact attenuation provided by commercially available PHP during simulated head impacts.MethodsA drop tower and Hybrid III headform measured the decrease in peak linear acceleration (gatten) provided by 12 PHP for front- and back-of-head impacts at low (clinically relevant: 3.5 m/s) and high (5.7 m/s) impact velocities.ResultsThe range of gatten across PHP was larger at the low velocity (56% and 41% for back and frontal impacts, respectively) vs. high velocity condition (27% and 38% for back and frontal impacts, respectively). A significant interaction between impact location and velocity was observed (p < .05), with significantly greater gatten for back-of-head compared to front-of-head impacts at the low impact velocity (19% mean difference). While not significant, there was a modest positive association between gatten and product padding thickness for back-of-head impacts (p = .095; r = 0.349).ConclusionThis study demonstrates the wide range in impact attenuation across commercially available PHP, and suggests that existing products provide greater impact attenuation during back-of-head impacts. These data may inform evidence-based decisions for clinicians and consumers and help drive industry innovation.

USA Football established five levels-of-contact to guide the intensity of high school football practices. The objective of this study was to examine head impact frequency and magnitude by levels-of-contact to determine which drills had the greatest head impact exposure. Our primary hypothesis was that there would be an incremental increase in season-long head impact exposure between levels-of-contact: air<bags<control<thud<live. This observational study included 24 high-school football players during all 46 practices, 1 scrimmage, 9 junior varsity and 10 varsity games in the 2019 season. Players wore a sensor-installed mouthguard that monitored head impact frequency, peak linear acceleration (PLA), and rotational acceleration (PRA). Practice/game drills were filmed and categorized into five levels-of-contact (air, bags, control, thud, live), and head impact data were assigned into one of five levels-of-contact. Player position was categorized into lineman, hybrid, and skill. A total of 6016 head impacts were recorded during 5 levels-of-contact throughout the season. In the overall sample, total number of impacts, sum of PLA, and PRA per player increased in a near incremental manner (air<bags<control = thud<live), where live drills had significantly higher cumulative frequency (113.7±17.8 hits/player) and magnitude [2,657.6±432.0 g (PLA), and 233.9 ± 40.1 krad/s2 (PRA)] than any other levels-of-contact, whereas air drills showed the lowest cumulative frequency (7.7±1.9 hits/player) and magnitude [176.9±42.5 g (PLA), PRA 16.7±4.2 krad/s2 (PRA)]. There was no significant position group difference in cumulative head impact frequency and magnitude in a season. Although there was no difference in average head impact magnitude across five levels-of-contact and by position group PLA (18.2–23.2g) and PRA (1.6–2.3krad/s2) per impact], high magnitude (60-100g and >100g) head impacts were more frequently observed during live and thud drills. Level-of-contact influences cumulative head impact frequency and magnitude in high-school football, with players incurring frequent, high magnitude head impacts during live, thud, and control. It is important to consider level-of-contact to refine clinical exposure guidelines to minimize head impact burden in high-school football.

Assessing women's lacrosse head impacts using finite element modelling.

While studies indicate that females experience a higher concussion risk and more severe outcomes in soccer heading compared to males, comprehensive data on the underlying factors contributing to these sex-based differences are lacking. This study investigates the sex differences in the head-to-ball impact kinematics among college-aged soccer headers in a laboratory-controlled setting. Forty subjects (20 females, 20 males) performed ten headers, and impact kinematics, including peak angular acceleration and velocity (PAA, PAV) and peak linear acceleration (PLA), were measured using mouthguards. Video recordings verified impacts and impact locations. Participants' head mass was estimated from their weights. The relationship between head mass and kinematic parameters was analyzed using Pearson correlation. The effects of head mass, sex, and impact location on kinematic parameters were assessed using MANOVA with and without head mass as a covariate. Results showed that head mass, larger in males than females, significantly affects PAA and PLA, the greater the head mass, the lower PAA and PLA. However, head mass has no effect on PAV. Females showed significantly higher PAA and PLA components but no significant differences in PAV. Impact location significantly influenced PAV, showing higher magnitudes for frontal impacts compared to top-front impacts, with no significant effects on PAA and PLA. Our results agree with epidemiological evidence that female soccer players face greater concussion risks than males, which can be attributed to their higher header-induced PAA. Future research could consider interventions like changing ball pressure, using protective headgear, and improving heading techniques to reduce high-magnitude accelerations in females.

The purpose of this study was to investigate the extent to which ice hockey facial protectors can decrease overall head acceleration during blunt impacts, as well as to identify whether attenuation differences exist between visors and cages. Commercial models of three cages and three visors were assessed. Blunt impacts were simulated, permitting the measurement of peak accelerations (PA) within the surrogate headform. Results indicated that face protectors, in combination with helmets, substantially reduced PA during blunt impacts within threshold safety limits (below 300g). In general, cages showed lower PA than visors. Differences between models were also observed during repeated impacts and impact site. In conclusion, this study demonstrates that facial protectors function beyond their role in solely preventing facial injuries, complementing the role of the helmet in attenuating head deceleration during impact. Consequently, the utilisation of facial protectors may reduce the severity and incidence of head injuries.

This study used a multidisciplinary approach to examine the brains of pediatric road trauma fatalities in the Sydney area over a 3-year period. The brains of 32 children (0-16 years) were examined: 20 pedestrians, nine passengers, and three cyclists. The extent and distribution of brain injury was assessed, peak linear head acceleration determined, and the severity of brain damage was compared to that previously reported for adults using the same scoring method. Skull fractures (20/32) and subarachnoid haemorrhage (22/32) were the commonest head injuries. In general, the neuropathology was similar to that seen in adults, with a high percentage of damage in the corpus callosum and gliding contusions within the subcortical white matter. Intracerebral hemorrhage was relatively rare. For frontal and occipital head impacts, the corpus callosum was the most injured part of the brain, followed by the deep central structures and the temporal lobes, whereas for lateral impacts, the injuries were more evenly distributed. Comparison of the current data for children with the vascular injury sector scores reported for adults suggests that the brains of children are more severely damaged for the same peak linear head acceleration.

As advanced helmet testing methodologies are developed, the effect headform selection may have on the biomechanical impact response must be considered. This study sought to assess response differences between two of the most commonly used headforms, the Hybrid III and National Operating Committee on Standards for Athletic Equipment headforms, through a series of helmeted impact tests. A total of 180 pendulum impact tests were conducted with three impactor velocities and six impact locations. Test condition–specific significant differences were found between the two headforms for peak linear and angular accelerations (α = 0.05), although differences tended to be small. On average, the National Operating Committee on Standards for Athletic Equipment headform experienced higher peak linear (3.7 ± 7.8%) and angular (12.0 ± 21.6%) accelerations, with some of the largest differences associated with impacts to the facemask. Without the facemask impacts, the average differences in linear (1.8 ± 6.0%) and angular (9.6 ± 15.9%) acceleration would be lower. No significant differences were found in coefficient of variation values for linear (Hybrid III: 2.6 ± 2.3%, National Operating Committee on Standards for Athletic Equipment: 2.0 ± 1.4%) or angular (Hybrid III: 4.9 ± 4.0%; National Operating Committee on Standards for Athletic Equipment: 5.2 ± 5.8%) acceleration. These data have application toward development and validation of future helmet evaluation protocols and standards.

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