Consensus Head Acceleration Measurement Practices (CHAMP): Laboratory Validation of Wearable Head Kinematic Devices

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.

Head impact exposure in popular contact sports is not well understood, especially in the youth population, despite recent advances in impact-sensing technology which has allowed widespread collection of real-time head impact data. Previous studies indicate that a custom-instrumented mouthpiece is a superior method for collecting accurate head acceleration data. The objective of this study was to evaluate the efficacy of mounting a sensor device inside an acrylic retainer form factor to measure six-degrees-of-freedom (6DOF) head kinematic response. This study compares 6DOF mouthpiece kinematics at the head center of gravity (CG) to kinematics measured by an anthropomorphic test device (ATD). This study found that when instrumentation is mounted in the rigid retainer form factor, there is good coupling with the upper dentition and highly accurate kinematic results compared to the ATD. Peak head kinematics were correlated with r2 > 0.98 for both rotational velocity and linear acceleration and r2 = 0.93 for rotational acceleration. These results indicate that a rigid retainer-based form factor is an accurate and promising method of collecting head impact data. This device can be used to study head impacts in helmeted contact sports such as football, hockey, and lacrosse as well as nonhelmeted sports such as soccer and basketball. Understanding the magnitude and frequency of impacts sustained in various sports using an accurate head impact sensor, such as the one presented in this study, will improve our understanding of head impact exposure and sports-related concussion.

Wearable devices are developed to measure head impact kinematics but are intrinsically noisy because of the imperfect interface with human bodies. This study aimed to improve the head impact kinematics measurements obtained from instrumented mouthguards using deep learning to enhance traumatic brain injury (TBI) risk monitoring. We developed one-dimensional convolutional neural network (1D-CNN) models to denoise mouthguard kinematics measurements for tri-axial linear acceleration and tri-axial angular velocity from 163 laboratory dummy head impacts. The performance of the denoising models was evaluated on three levels: kinematics, brain injury criteria, and tissue-level strain and strain rate. Additionally, we performed a blind test on an on-field dataset of 118 college football impacts and a test on 413 post-mortem human subject (PMHS) impacts. On the dummy head impacts, the denoised kinematics showed better correlation with reference kinematics, with relative reductions of 36% for pointwise root mean squared error and 56% for peak absolute error. Absolute errors in six brain injury criteria were reduced by a mean of 82%. For maximum principal strain and maximum principal strain rate, the mean error reduction was 35% and 69%, respectively. On the PMHS impacts, similar denoising effects were observed and the peak kinematics after denoising were more accurate (relative error reduction for 10% noisiest impacts was 75.6%). The 1D-CNN denoising models effectively reduced errors in mouthguard-derived kinematics measurements on dummy and PMHS impacts. This study provides a novel approach for denoising head kinematics measurements in dummy and PMHS impacts, which can be further validated on more real-human kinematics data before real-world applications.

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.

ObjectiveAssess utility of wearable impact sensors to monitor and reduce cumulative brain injury risks in athletic and military environments.DesignAnalysis of results generated in multiple laboratory and on-field cohort studies.SettingYouth, college,...

&lt;div&gt;Athletes may sustain numerous head impacts during sport, leading to potential neurological consequences. Wearable sensors enable real-world head impact data collection, offering insight into sport-specific brain injury mechanisms. Most instrumented mouthguard studies focus on a single sport, lacking a quantitative comparison of head impact biomechanics across sports. Additionally, direct comparison of prior studies can be challenging due to variabilities in methodology and data processing. Therefore, we gathered head impact data across multiple sports and processed all data using a uniform processing pipeline to enable direct comparisons of impact biomechanics. Our aim was to compare peak kinematics, impulse durations, and head impact directionality across ice hockey, American football, rugby, and soccer. We found that American football had the highest magnitude of head impact kinematics and observed directionality differences in linear and angular kinematics between sports. On the other hand, there were no significant differences in impulse durations, which was unexpected given the different impacting objects and protective equipment across sports. In future work, we aim to expand our dataset to better match sports for understanding the influence of sex, equipment, and playstyle on head impact biomechanics.&lt;/div&gt;

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 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.

With the concern of concussion risk and repetitive head impacts in youth football, organizations have adopted rules that limit contact during practice. However, rule changes are not ubiquitous among organizations and are challenging to monitor and enforce. Ultimately, football practice activities are determined by coaches, but it is unknown whether providing objective data to coaches relating activities to their athletes' head impact exposure (HIE) would alter practice structure or help reduce HIE. This study evaluated the effect of coach awareness of HIE on practice structure over time. Head impact data from three intervention (56 players) and three control (38 players) teams were collected over two youth football seasons. Athletes were instrumented with the Head Impact Telemetry (HIT) System and time-synchronized video was recorded for practices and games. Impact frequencies and head accelerations were compiled into weekly HIE practice and game reports and shared with the head coach of each intervention team. Time per drill, impact rate, and impact magnitude were compared across three time frames (pre-season, mid-season, and late-season) using generalized linear models. Control teams had higher impact rates than intervention teams in all drills across time frames. Among all teams, 95th percentile linear and rotational accelerations were highest during mid-season. Among intervention teams, more time was spent on scrimmage and skill development from pre-season to late-season, with less time spent on tackling. This study suggests that receiving objective data informing HIE in practice may contribute to changes in practice structure and help inform intervention efforts to improve head impact safety in football.

Background: A fall is the most common falsely reported injury scenario when a young child presents for medical care and the caregiver is concealing abuse. There is a lack of reliably witnessed falls with known outcomes to aid in the distinction between accidental and abusive injuries. Objectives: The objectives of this study were to characterize video-recorded short distance falls involving young children in a childcare setting, to identify body regions most commonly impacted in these short distance falls, to characterize the head biomechanics of these falls, and describe fall characteristics. Additionally, physics-based models were used to predict fall biomechanics in a subset of these falls. Methods: This study included children aged 12-25 months. Two childcare classrooms and a playground were each equipped with 3 digital video cameras. Video recordings involving falls were extracted for analysis. Falls were characterized by various factors (such as fall type; initial condition; fall dynamics; etc.), and these were analyzed for frequency. Descriptive statistics were performed on outcome measures. The distribution of impacted/contacted body regions was described and projected onto a child body map. Falls with biomechanical data from wearable devices were characterized by head impact and analyzed. It was hypothesized that head accelerations and velocities will be greater in falls with head impact than in falls without head impact. To analyze the accuracy and usefulness of physics-based biomechanical models, lumped mass, single rod, and inverted pendulum physics-based models were developed for previously conducted ATD falls and falls involving head impact from the childcare center. It was hypothesized that these models could accurately predict head biomechanical measures. Results: 100 video-recorded falls involving 8 children, age 17-25 months (mean ± SD: 20 ± 2 months) were characterized. 65% of falls involved boys, and 64% of falls occurred indoors in a classroom. No injuries occurred in any fall. The most common first contact body regions were the soles of the feet. The most common primary impact body region was the palms of the hands; bilateral shins, bilateral knees, and buttocks were also commonly impacted. Replicated ATD falls and select childcare center falls with SIM G outputs were mathematically modelled, and it was determined that mathematical physics-based models could reasonably predict biomechanical outcomes from short-distance falls. Conclusions: This study resulted in a dataset of 100 reliably witnessed video-recorded falls involving young children in a childcare center setting. Body region contact/impact maps for first contact, primary impact, and secondary impact

Wearable devices for tracking physical activity in the community after an acquired brain injury: A systematic review.

The objective of this research was to characterize head impacts with a validated mouthpiece sensor in competitive youth female soccer players during a single season with a validated mouthpiece sensor. Participants included 14 youth female soccer athletes across 2 club-level teams at different age levels (team 1, ages 12-13y; team 2, ages 14-15y). Head impact and time-synchronized video data were collected for 66 practices and games. Video data were reviewed to characterize the type and frequency of contact experienced by each athlete. A total of 2216 contact scenarios were observed; heading the ball (n = 681, 30.7%) was most common. Other observed contact scenarios included collisions, dives, falls, and unintentional ball contact. Team 1 experienced a higher rate of headers per player per hour of play than team 2, while team 2 experienced a higher rate of collisions and dives. A total of 935 video-verified contact scenarios were concurrent with recorded head kinematics. While headers resulted in a maximum linear acceleration of 56.1g, the less frequent head-to-head collisions (n = 6) resulted in a maximum of 113.5g. The results of this study improve the understanding of head impact exposure in youth female soccer players and inform head impact exposure reduction in youth soccer.

ObjectiveTo compare the severity of head impacts between professional and Division I (D-I) collegiate football games for the purpose of improving protective equipment.MethodsA total of 243 football players from the...

The aim of this study was to quantify head impact exposure for a collegiate women's soccer team over the course of the 2014 season. Observational and prospective study. Virginia Tech women's soccer games and practices. Twenty-six collegiate level women's soccer players with a mean player age of 19 ± 1. Participating players were instrumented with head impact sensors for biomechanical analysis. Video recordings of each event were used to manually verify each impact sustained. Head impact counts by player position and impact situation. The sensors collected data from a total of 17 865 accelerative events, 8999 of which were classified as head impacts. Of these, a total of 1703 impacts were positively identified (19% of total real impacts recorded by sensor), 90% of which were associated with heading the ball. The average number of impacts per player per practice or game was 1.86 ± 1.42. Exposure to head impact varied by player position. Head impact exposure was quantified through 2 different methods, which illustrated the challenges associated with autonomously collecting acceleration data with head impact sensors. Users of head impact data must exercise caution when interpreting on-field head impact sensor data.

BackgroundHead impacts in sports produce brain deformation, which can damage brain white matter leading to short/long-term effects. Quantifying white matter deformation (strain) in different sports allows developing tailored prevention and...