National Operating Committee On Standards For Athletic Equipment Research Articles

Advancing Commotio cordis Safety Standards Using the Total Human Models for Safety (THUMS).

Commotio cordis is one of the leading causes of sudden cardiac death in youth baseball. Currently, there are chest protector regulations regarding the prevention of Commotio cordis in baseball and lacrosse; however, they are not fully optimized. For the advancement of Commotio cordis safety, it is vital to include various age groups and a variety of impact angles in the testing process. This study employed finite element models and simulated Commotio cordis-inducing baseball collisions for different velocities, impact angles, and age groups. Commotio cordis risk response was characterized in terms of left ventricular strain and pressure, chest band and rib deformation, and force from impact. Normalized rib and chest band deformation when correlated with left ventricular strain resulted in R2 = 0.72, and R2 = 0.76, while left ventricular pressure resulted in R2 = 0.77, R2 = 0.68 across all velocities and impact angles in the child models. By contrast, the resultant reaction force risk metric as used by the National Operating Committee on Standards for Athletic Equipment (NOCSAE) demonstrated a correlation of R2 = 0.20 in the child models to ventricular strain, while illustrating a correlation to pressure of R2 = 0.74. When exploring future revisions to Commotio cordis safety requirements, the inclusion of deformation-related risk metrics at the level of the left ventricle should be considered.

The effect of the head surrogate on the performance of bicycle helmets

Inconsistent results have been reported for helmeted impact responses between the two most commonly used headforms: The National Operating Committee on Standards for Athletic Equipment (NOCSAE) and the Hybrid III (HIII). There is a need to understand the reasons for the different responses of the headforms so that helmet protection may be discerned independent of the headform. In this study, the kinematic response and brain injury measures of the NOCSAE and HIII headforms at three impact orientations with three helmet models on an inclined anvil were compared. The results showed that the peak linear acceleration from the two headforms were within 6.3% on average for all impacts. However, despite the higher moment of inertia of the HIII headform, it did not have a consistently lower rotational acceleration compared to the NOCSAE headform. The differing headform rotational responses were primarily due to differences in the headforms’ center of gravity location. This led to differences in couples and accelerations, which tended to be most severe in frontal impact orientations. The variation in rotational responses of the headforms seems to be also dependent on the helmet type, with helmet A having greater variation compared to helmets B and C. Differences in the rotational kinematics of the two headforms led to a 47% average difference in their brain injury measures.

A destructible headform for the assessment of sports impacts

Commercially available headforms, such as the Hybrid-III and EN 960 headforms, have been used effectively to investigate the mechanics of head impacts. These headforms may result in accelerations that are unrepresentative of a human head in some impact scenarios. This may be important when considering impacts that produce areas of high pressure, since skull deformation and resonance excitation may influence the dynamic response. The National Operating Committee on Standards for Athletic Equipment (NOCSAE) headform may produce a more suitable response during these types of impacts due to the more representative skull component. However, permanent deformation may occur in some unprotected impact scenarios, resulting in the entire headform needing to be replaced. This paper outlines the development of a novel, modular and destructible headform (LU headform) that can be used in potentially destructive testing, where individual components can be replaced. The LU headform was modelled after a UK 50th percentile male. The inertial properties of the LU headform were within 6% of those observed in humans. The skull simulant properties were within the range of values reported for human tissue in two build orientations, but lower in one build orientation. The lowest and highest resonance frequencies observed in the headform model were within 5% of those observed in humans. Drop and projectile tests were conducted in line with previous cadaver tests with the observed accelerations within the range reported for post-mortem human subjects. The LU headform offers a practical means of simulating head dynamics during localised unprotected impacts or in protected impacts where local deformation and/or resonance frequency excitation remains possible.

Reduction of High School Ice Hockey Injuries With Implementation of New Checking/Boarding Rules.

Evaluate whether rule changes by the National Federation of State High School Associations (NFHS) were associated with reduced injury rates in US high school ice hockey players. We compared injury rates for the 3 seasons before the rule changes (2011-2012, 2012-2013, and 2013-2014) with the 2 subsequent seasons (2014-2015 and 2015-2016) using data from the High School Reporting Information Online (RIO) database. Convenience sample of US high schools. High school ice hockey athletes. The sports injury surveillance system that supplied the data for this study was funded in part by the Centers for Disease Control and Prevention (grant Nos. R49/CE000674-01, R49/CE001172-01, and R49/CE002106-01) as well as research funding contributions of the NFHS, National Operating Committee on Standards for Athletic Equipment (NOCSAE), DonJoy Orthotics, and EyeBlack. The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention or any other funding agency. In the 2014 to 2015 ice hockey season, the NFHS increased the penalty for boarding (illegally causing opponent to be thrown violently into the boards) and for checking from behind. Injury rates and mechanism of injury. There was a statistically significant 40% reduction in rates of injury attributed to being checked in the 2 seasons after the rule changes (5.0 injuries per 10 000 athlete exposures) compared with the 3 previous seasons (8.3) (rate ratio = 0.60, P = 0.002). There were no significant differences in overall injury rates (P = 0.12) or injury rates due to checking (P = 0.27), contact with the boards (P = 0.31), or contact with another player (P = 0.55). Among US high school ice hockey athletes, implementation of stricter penalties for boarding and checking from behind was associated with a significant decrease in injury rate due to being checked. Rates of injury due to other mechanisms were not significantly altered, suggesting the rule changes achieved their targeted effect.

Relating on-field youth football head impacts to pneumatic ram laboratory testing procedures.

A youth-specific football helmet testing standard has been proposed to address the physical and biomechanical differences between adult and youth football players. This study sought to relate the proposed youth standard-defined laboratory impacts to on-field head impacts collected from youth football players. Head impact data from 112 youth football players (ages 9-14) were collected through the use of helmet-mounted accelerometer arrays. These head impacts were filtered to only include those that resided in corridors near prescribed National Operating Committee on Standards for Athletic Equipment (NOCSAE) impact locations. Peak linear head acceleration and peak rotational head acceleration magnitudes collected from pneumatic ram impactor tests as specified by the proposed NOCSAE youth standard were compared to the distribution of on-field head impacts. All laboratory impact tests were among the top 10% in terms of magnitude for Severity Index and peak rotational acceleration of matched location head impacts experienced by youth football players. As concussive head impacts are among the most severe impacts experienced on the field, a safety standard geared toward mitigating concussion should assess the most severe on-field head impacts. This proposed testing standard may be refined as more becomes known regarding the biomechanics of concussion among youth athletes.

Determinants Of Head Impact Exposure In Youth Football

Concussions are on the minds of many football players, parents and coaches; but attention has increased toward the potentially damaging effects of repetitive, subconcussive head impacts, particularly among youth football players. Advocates of the sport are looking for ways to improve player safety and reduce the potential risk of long-term brain abnormalities. PURPOSE: To identify intrinsic and extrinsic characteristics of play associated with head impact exposure in youth football. METHODS: Head impacts from one youth football team (7th & 8th grade) were measured during every practice and game during the 2018 & 2019 football seasons via a sideline head impact telemetry system and subsequently evaluated using video collected during each session. Each verified head impact was scored using a validated rubric consisting of up to 12 discrete characteristics of play (5 intrinsic, 7 extrinsic). The mean, median and 95th percentile linear acceleration (LA) was calculated for each play characteristic. RESULTS: Over two seasons, 1202 practice (median LA: 19.90 g) and 1571 game (median LA: 21.00 g) head impacts (2773 total) were examined. The “kickoff” (n = 95 impacts; 6% of all game impacts) had the highest 95th percentile LA (69.89 g) among all game play types (e.g., “run”, “pass”, “punt”, etc.). Impacts that occurred “outside the hash marks” (61.75 g) and in the “redzone” (59.40 g) had the highest 95th percentile LA rankings among horizontal and vertical field positions, respectively. When players did not anticipate being hit (n = 53; 1.9% of all impacts), head impacts had a 95th percentile LA of 69.52 g, compared to 47.02 g when they anticipated the impact. Head impacts resulting from players’ helmets hitting the ground (95th percentile LA: 72.94 g) accounted for 11.6% of all impacts (n = 323). CONCLUSIONS: These data indicate that certain, modifiable characteristics of play are associated with higher magnitude head impacts in youth football. Additional research is warranted to continue to examine practice and game situations (extrinsic characteristics) that produce higher magnitude head impacts, which could assist football-governing bodies in developing or modifying policy guidelines to help make the game safer. Supported by a grant from The National Operating Committee on Standards for Athletic Equipment (NOCSAE).

Development and Multi-Scale Validation of a Finite Element Football Helmet Model

Head injury is a growing concern within contact sports, including American football. Computational tools such as finite element (FE) models provide an avenue for researchers to study, and potentially optimize safety tools, such as helmets. The goal of this study was to develop an accurate representative helmet model that could be used in further study of head injury to mitigate the toll of concussions in contact sports. An FE model of a Schutt Air XP Pro football helmet was developed through three major steps: geometry development, material characterization, and model validation. The fully assembled helmet model was fit onto a Hybrid III dummy head–neck model and National Operating Committee on Standards for Athletic Equipment (NOCSAE) head model and validated through a series of 67 representative impacts similar to those experienced by a football player. The kinematic and kinetic response of the model was compared to the response of the physical experiments, which included force, head linear acceleration, head angular velocity, and carriage acceleration. The outputs between the model and the physical tests were quantitatively evaluated using CORelation and Analysis (CORA), amounting to an overall averaged score of 0.76. The model described in this study has been extensively validated and can function as a building block for innovation in player safety.

Comparison of head impact attenuation capabilities between a standard American football helmet and novel protective equipment that couples a helmet and shoulder pads

Concussive and subconcussive sports-related head impacts are common in the United States, particularly in American football. Football helmets are constantly improving upon their predecessors and are proven to reduce head impact kinematics and the risk of sports-related head injury. All football helmets are required to pass certification testing overseen by the National Operating Committee on Standards for Athletic Equipment (NOCSAE) before they are permitted for use. A new advance in protective equipment involves coupling a helmet and shoulder pads as one connected piece of protective equipment. These protective gears cannot be tested using the standard NOCSAE method as they are worn over a user’s head, neck, and upper torso. We aimed to test the effectiveness of a prototype of a coupled, one-piece design, relative to a standard football helmet, using a custom drop tower method of testing. Relative to the standard football helmet, the coupled design reduced measures of peak linear acceleration at front, side, and rear impacts (p < .001) and peak rotational acceleration at all tested head locations (p < .004). The coupled design was also more effective than the standard helmet in attenuating the resultant upper neck force (p < .004) at all tested head impact locations and resultant upper neck moment at rear and side impact locations (p < .048). Future iterations of coupled, one-piece designs should use the results of this study to make improvements to the device, and further investigations on the effectiveness and safety implications of the protective gear are necessary.

Influence of ATD versus PMHS reference sensor inputs on computational brain response in frontal impacts to advanced combat helmet (ACH)

ABSTRACTObjective: This study analyzed the influence of reference sensor inputs from anthropomorphic test devices (ATDs) versus postmortem human subjects (PMHSs) on simulations of frontal blunt impacts to the advanced combat helmet (ACH).Methods: A rigid-arm pendulum was used to generate frontal impacts to ACHs mounted on ATDs and PMHS. An appropriately sized ACH was selected according to standard fitting guidelines. The National Operating Committee on Standards for Athletic Equipment (NOCSAE) head was selected for ATD tests due to shape features that enabled a realistic helmet fit. A custom procedure was used to mount a reference sensor internally near the center of gravity (CG) of the PMHS. Reference sensor data from the head CG were used as inputs for the Simulated Injury Monitor (SIMon). Brain responses were assessed with the cumulative strain damage measure set at 10%, or CSDM(10).Results: Compared to ATD tests, PMHS tests produced 18.7% higher peak linear accelerations and 5.2% higher peak angular velocities. Average times to peak for linear accelerations were relatively similar between ATDs (5.5 ms) and PMHSs (5.8 ms). However, times to peak for angular velocities were higher by a factor of up to 3.4 for PMHSs compared to ATDs. Values for were also higher by a factor of up to 13.1 when PMHS inputs were used for SIMon.Conclusions: The preliminary findings of this work indicate that small differences in ATD versus PMHS head kinematics could lead to large differences in strain-derived brain injury metrics such as CSDM.

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.

Inertial Properties of Football Helmets.

The inertial properties of a helmet play an important role in both athletic performance and head protection. In this study, we measured the inertial properties of 37 football helmets, a National Operating Committee on Standards for Athletic Equipment (NOCSAE) size 7¼ headform, and a 50th percentile male Hybrid III dummy head. The helmet measurements were taken with the helmets placed on the Hybrid III dummy head. The center of gravity and moment of inertia were measured about six axes (x, y, z, xy, yz, and xz), allowing for a complete description of the inertial properties of the head and helmets. Total helmet mass averaged 1834±231 g, split between the shell (1377±200 g) and the facemask (457±101 g). On average, the football helmets weighed 41±5% as much as the Hybrid III dummy head. The center of gravity of the helmeted head was 1.1±3.0 mm anterior and 10.3±1.9 mm superior to the center of gravity of the bare head. The moment of inertia of the helmeted head was approximately 2.2±0.2 times greater than the bare head about all axes.

Comparison of Impact Performance between Youth and Varsity Football Helmets.

Current youth football helmets, intended for players under the age of 14 years old, are similar in design and are tested under the same standard as varsity football helmets. This study evaluated the impact performance of matched youth and adult varsity football helmets. Eight helmet models were evaluated using an impact pendulum, with a modified National Operating Committee on Standards for Athletic Equipment (NOCSAE) medium sized headform mounted on a Hybrid III 50th percentile neck. Four locations on the helmet shell at three impact velocities were tested for three trials, for a total of 576 impact tests. Linear acceleration, rotational acceleration, and a concussion correlate were recorded for each test and a comparison between the youth and varsity helmets were made. It was found that the age group the helmet is intended for did not have a significant effect on the impact performance of the helmet in either linear acceleration, rotational acceleration, or concussion correlate. These results are likely due to the similarities in helmet design resulting from being tested to the same standard. Although it is unknown how a youth helmet should differ from a varsity helmet, differences in impact exposure, anthropometry, physiology, and injury tolerance are factors to consider. These data serves as a reference point for future youth-specific helmet design and helmet standards.

Quantifying the effect of the facemask on helmet performance

Evaluating and improving helmet design play a crucial role in reducing sports-related concussions. Despite widespread use of facemasks by football and hockey players, no helmet standards currently exist to test helmets equipped with facemasks. The purpose of this study was to determine the effect that attached facial protection has on the head kinematics resulting from impacts to the helmet shell. Helmets were fit to a modified NOCSAE (National Operating Committee on Standards for Athletic Equipment) headform and subjected to blows from a pneumatic impactor. A total of 240 impact tests were performed to evaluate the effect of the facemask on four helmet models (two for football, two for hockey). For each helmet model, one sample was tested with a facemask and another without a facemask. Tests were conducted at two impact velocities (6, 9 m/s) and three impact locations (front, side, and rear boss) for a total of six impact conditions. Five trials were performed for each helmet sample at each condition. Two-factor analyses of variance were used to quantify effects on linear and rotational head acceleration and Severity Index due to impact location and facemask presence. Significant effects varied by helmet model and impact location and were more commonly associated with football helmets. Differences in facemask effects between sports are likely attributed to differences in facemask-shell attachment mechanisms, and differences in the structure of the facemask itself. The effects of the facemask on linear and rotational acceleration were small, approximately 5% for both football and hockey helmets. On average, peak accelerations were decreased with the addition of a facemask, but individual differences were mixed and varied by helmet type and impact location. These small differences would not greatly affect impact performance tests in the lab. The results of this study have direct applications toward helmet standard development.

An Examination of Adolescent Athletes and Non-athletes on Baseline Neuropsychological Test Scores

An estimated 15.3 million adolescent students are enrolled in high school. However, approximately 7.6 million participate in athletics. Research has examined different demographics in high school athletes, however athletic participation may play a larger role in test performance than previously thought. Currently, research involving concussion assessment utilizes non-injured athletes as controls, but due to the intense nature of athletics, this may not be appropriate. PURPOSE: Examine differences between athletes and non-athletes using a common computerized neuropsychological test. METHODS: 662 adolescent high school students (athletes (ATH): n = 383, non-athletes (NON): n = 279) were administered a computerized neuropsychological test battery (ImPACT ®) during baseline concussion assessment. Differences between groups were calculated using a one-way ANOVA. All statistical analyses were conducted using SPSS 23.0. Significance levels were set a priori at p ≤ .05. RESULTS: Statistically significant differences were found between ATH and NON in Composite Verbal Memory (F(1, 660) = 4.653, p = .031), Composite Reaction Time (F(1, 660) = 15.869, p ≤ .001), and Total Symptom Score (F(1, 660) = 38.996, p ≤ .001). Non-athletes performed better on verbal memory and reported more symptoms, while ATH had faster reaction times. No significant differences were found in composite visual memory, composite visual motor, and composite impulse control (p ≥ 0.05). CONCLUSION: Significant differences were found between ATH and NON for symptom reporting, verbal memory, and reaction time. Athletes may have additional training or motivational factors during testing which may affect participation or return to play decisions. Overall, these significant differences in baseline performance should be accounted for when making concussion diagnostic and management decisions. Future research should be conducted to examine the influence of athletic participation on the recovery process to see if non-athletes can be used as healthy controls. Supported by: The National Operating Committee on Standards for Athletic Equipment (NOCSAE).

Comparison of shell-facemask responses in American football helmets during NOCSAE drop tests

This study compares drop tower tests of four commonly used football helmets, under the National Operating Committee on Standards for Athletic Equipment (NOCSAE) football helmet standard, to show that the tests need modification to include the facemask. In our study, the need for a more robust systematic approach to football helmet testing procedures is emphasized by comparing the Head Injury Criterion (HIC), the Gadd Severity Index (SI), and peak acceleration values for different helmets at different locations on the helmet under modified NOCSAE standard drop tower tests. Drop tests were performed on four modern football helmets at eight impact locations (front, front boss, side, rear, rear boss, top, front top, and front top boss), two different impact velocities (5.46 and 4.88 m/s), and two helmet configurations (“with facemasks” and “without facemasks”). Statistically significant differences (p < 0.05) were found in 41% of the comparisons between “with facemasks” and “without facemasks”. Addition of the facemask resulted in an increased HIC, SI, and peak acceleration response measures in 62% of these cases. For example, the stiffening boundary conditions arising from the attached facemask can decrease the helmet performance by up to 50% depending on the impact location when considering the peak acceleration (p < 0.001) as a metric. In terms of location, the top and front top impacts gave the largest HIC, SI, and peak acceleration values. In summary, these comparative drop test results revealed that the current NOCSAE test methods need improvement by attaching the facemasks to helmets and by including two new helmet impact locations (front top and front top boss). The modified NOCSAE football helmet standard test gives a more accurate representation of a helmet’s performance and its ability to mitigate on-field impact.

Modified Drop Tower Impact Tests for American Football Helmets.

A modified National Operating Committee on Standards for Athletic Equipment (NOCSAE) test method for American football helmet drop impact test standards is presented that would provide better assessment of a helmet's on-field impact performance by including a faceguard on the helmet. In this study, a merger of faceguard and helmet test standards is proposed. The need for a more robust systematic approach to football helmet testing procedures is emphasized by comparing representative results of the Head Injury Criterion (HIC), Severity Index (SI), and peak acceleration values for different helmets at different helmet locations under modified NOCSAE standard drop tower tests. Essentially, these comparative drop test results revealed that the faceguard adds a stiffening kinematic constraint to the shell that lessens total energy absorption. The current NOCSAE standard test methods can be improved to represent on-field helmet hits by attaching the faceguards to helmets and by including two new helmet impact locations (Front Top and Front Top Boss). The reported football helmet test method gives a more accurate representation of a helmet's performance and its ability to mitigate on-field impacts while promoting safer football helmets.

Impact attenuation capabilities of football and lacrosse helmets

Although the National Operating Committee on Standards for Athletic Equipment (NOCSAE) standards are similar for football and lacrosse helmets, it remains unknown how helmets for each sport compare on drop tests. Due to the increased concern over head injury in sport and the rapid growth in lacrosse participation, it is useful to compare the performance of various football and lacrosse helmets. Therefore, the goal of this study was to document the impact attenuation properties of football and lacrosse helmets and to identify the relative performance between helmets for the two sports. Six models of football and six models of lacrosse helmets were tested using a drop tower at three prescribed velocities and six locations on the helmets. A repeated measures ANOVA was conducted to determine the effect of sport on Gadd Severity Index (GSI) scores and linear accelerations. The interaction between location and sport was significant at the low (F2.64,89.71=7.68, P<.001, η2=.025), medium (F2.85,96.85=16.78, P<.001, η2=.085), and high (F2.96,100.69=16.67, P<.001, η2=.093) velocities for GSI scores. When comparing peak acceleration results, we found a significant interaction between location and sport for the medium (F3.40,115.616=5.57, P=.001, ω2=.031) and high (F3.46,117.50=6.42, P<.001, ω2=.047) velocities. Features of football helmet design provide superior protection compared to lacrosse helmets. Further investigation of helmet design features across sports will yield insight into how design features influence helmet performance during laboratory testing.

Brain injury in sports.

Helmets are used for sports, military, and transportation to protect against impact forces and associated injuries. The common belief among end users is that the helmet protects the whole head, including the brain. However, current consensus among biomechanists and sports neurologists indicates that helmets do not provide significant protection against concussion and brain injuries. In this paper the authors present existing scientific evidence on the mechanisms underlying traumatic head and brain injuries, along with a biomechanical evaluation of 21 current and retired football helmets. The National Operating Committee on Standards for Athletic Equipment (NOCSAE) standard test apparatus was modified and validated for impact testing of protective headwear to include the measurement of both linear and angular kinematics. From a drop height of 2.0 m onto a flat steel anvil, each football helmet was impacted 5 times in the occipital area. Skull fracture risk was determined for each of the current varsity football helmets by calculating the percentage reduction in linear acceleration relative to a 140-g skull fracture threshold. Risk of subdural hematoma was determined by calculating the percentage reduction in angular acceleration relative to the bridging vein failure threshold, computed as a function of impact duration. Ranking the helmets according to their performance under these criteria, the authors determined that the Schutt Vengeance performed the best overall. The study findings demonstrated that not all football helmets provide equal or adequate protection against either focal head injuries or traumatic brain injuries. In fact, some of the most popular helmets on the field ranked among the worst. While protection is improving, none of the current or retired varsity football helmets can provide absolute protection against brain injuries, including concussions and subdural hematomas. To maximize protection against head and brain injuries for football players of all ages, the authors propose thresholds for all sports helmets based on a peak linear acceleration no greater than 90 g and a peak angular acceleration not exceeding 1700 rad/sec(2).

Impact attenuation properties of new and used lacrosse helmets

The National Operating Committee on Standards for Athletic Equipment (NOCSAE) has developed impact attenuation thresholds that protective helmets worn in sport must meet to be commercially available in an attempt to prevent injury. It remains unknown how normal helmet use in athletic activity alters the force attenuation ability of lacrosse helmets. We tested 3 new and 3 randomly selected used helmets from 2 popular lacrosse models (Cascade Pro7, Cascade CPXR). All used helmets had been worn for 3 collegiate seasons prior to testing and had never been refurbished. Helmets were drop-tested using 3 prescribed impact velocities at 6 locations according to the NOCSAE lacrosse helmet standard, and we compared the Gadd Severity Index (GSI) scores between new and used helmets using a repeated measure ANOVA with location as the repeated variable and data separated by impact velocity. All 12 helmets passed the NOCSAE GSI threshold for all testing conditions; however 1 used helmet shell cracked resulting in a failed test. We found a significant main effect for helmet age at the low (F5,50=2.98, P=.02), medium (F5,50=3.71, P=.006), and high (F5,50=2.70, P=.03) velocities. We suspect that helmet use can degrade materials under some conditions, but improve performance in others due to changes in helmet composition from use. The clinical implications of the differences in GSI scores noted remain unclear. Because one helmet shell cracked resulting in a failed test, used helmets should be regularly inspected for cracks or other signs of mechanical fatigue that may weaken helmet integrity.

Simulation, fabrication and impact testing of a novel football helmet padding system that decreases rotational acceleration

Recent studies suggest that concussion may be associated with long-term neurological sequelae. Both linear impact and rotational acceleration have been identified as contributors to concussion and traumatic brain injury (TBI). Modern football helmets are designed according to the National Operating Committee on Standards for Athletic Equipment (NOCSAE) standard for protection from linear impact, without consideration of protection from rotational injury. A multidisciplinary team was assembled with expertise in brain injury, computational modeling, and materials engineering to design, fabricate and impact test a novel helmet padding system. A rotational fixture with magnesium headform and linear impactor was constructed using a rotary encoder to enable measurement of z axis rotational angle, velocity and acceleration. Helmet padding material designs were evaluated using finite element (FE) computational modeling, fabricated to specification and then impact tested. Models from two different manufacturers were retrofit with prototype pads and then compared with unmodified versions for attenuation of rotational acceleration. The helmets were then tested using a standard NOCSAE drop apparatus and headform for linear acceleration performance. Large-size Riddell Revolution and Schutt ION4D helmets retrofit with prototype padding demonstrated 21.6 and 33.6 % decreased peak z axis rotational acceleration following a 3.2 m/s side impact compared with their respective unmodified commercial models (717.7 vs. 914.0 rad/s2 and 768.4 vs. 1,158.6 rad/s2, p < 0.0001, respectively). The improved performance effect appeared consistent over at least 50 impacts without evidence of early material degradation or helmet damage. Compared with unmodified versions, drop test performance for hybridized helmets, measured by Peak G and severity index (SI), were comparable for most, but were worse for rear (Riddell Revolution) and side (Schutt ION4D) impact conditions. Rotational acceleration from side impacts may be attenuated by directed helmet design while maintaining acceptable linear impact performance. Future work will focus on optimization and durability testing of prototype padding for larger impacts.