Consensus Head Acceleration Measurement Practices (CHAMP): Origins, Methods, Transparency and Disclosure.

The use of head kinematic measurement devices has recently proliferated owing to technology advances that make such measurement more feasible. In parallel, demand to understand the biomechanics of head impacts and injury in sports and the military has increased as the burden of such loading on the brain has received focused attention. As a result, the field has matured to the point of needing methodological guidelines to improve the rigor and consistency of research and reduce the risk of scientific bias. To this end, a diverse group of scientists undertook a comprehensive effort to define current best practices in head kinematic measurement, culminating in a series of manuscripts outlining consensus methodologies and companion summary statements. Summary statements were discussed, revised, and voted upon at the Consensus Head Acceleration Measurement Practices (CHAMP) Conference in March 2022. This manuscript summarizes the motivation and methods of the consensus process and introduces recommended reporting checklists to be used to increase transparency and rigor of future experimental design and publication of work in this field. The checklists provide an accessible means for researchers to apply the best practices summarized in the companion manuscripts when reporting studies utilizing head kinematic measurement in sport and military settings.

Best Practices for Conducting Physical Reconstructions of Head Impacts in Sport.

Physical reconstructions are a valuable methodology for quantifying head kinematics in sports impacts. By recreating the motion of human heads observed in video using instrumented test dummies in a laboratory, physical reconstructions allow for in-depth study of real-world head impacts using well-established surrogates such as the Hybrid III crash test dummy. The purpose of this paper is to review all aspects of the physical reconstruction methodology and discuss the advantages and limitations associated with different choices in case selection, study design, test surrogate, test apparatus, text matrix, instrumentation, and data processing. Physical reconstructions require significant resources to perform and are therefore typically limited to small sample sizes and a case series or case-control study design. Their accuracy may also be limited by a lack of dummy biofidelity. The accuracy, repeatability, and sensitivity of the reconstruction process can be characterized and improved by good laboratory practices and iterative testing. Because wearable sensors have their own limitations and are not available or practical for many sports, physical reconstructions will continue to provide a useful and complementary approach to measuring head acceleration in sport for the foreseeable future.

Video Analysis and Verification of Direct Head Impacts Recorded by Wearable Sensors in Junior Rugby League Players.

BACKGROUND: Rugby league is a high-intensity collision sport that carries a risk of concussion. Youth athletes are considered to be more vulnerable and take longer to recover from concussion than adult athletes. PURPOSE: To review head impact events in elite-level junior representative rugby league and to verify and describe characteristics of X-patchTM-recorded impacts via video analysis. STUDY DESIGN: Observational case series. METHODS: The X-patchTM was used on twenty-one adolescent players (thirteen forwards and eight backs) during a 2017 junior representative rugby league competition. Game-day footage, recorded by a trained videographer from a single camera, was synchronised with X-patchTM-recorded timestamped events. Impacts were double verified by video review. Impact rates, playing characteristics, and gameplay situations were described. RESULTS: The X-patchTM-recorded 624 impacts ≥ 20g between game start and finish, of which 564 (90.4%) were verified on video. Upon video review, 413 (73.2%) of all verified impacts ≥ 20g where determined to be direct head impacts. Direct head impacts ≥ 20g occurred at a rate of 5.2 impacts per game hour; 7.6 for forwards and 3.0 for backs (range = 0-18.2). A defender's arm directly impacting the head of the ball carrier was the most common event, accounting for 21.3% (n = 120) of all impacts, and 46.7% of all "hit-up" impacts. There were no medically diagnosed concussions during the competition. CONCLUSION: The majority (90.4%) of head impacts ≥ 20g recorded by the X-patchTM sensor were verified by video. Double verification of direct head impacts in addition to cross-verification of sensor-recorded impacts using a secondary source such as synchronised video review can be used to ensure accuracy and validation of data.

Injury deaths in Australian sport and recreation: Identifying and assessing priorities for prevention.

INTRODUCTION: Sport and recreation is beneficial for health and wellbeing but comes with a probability of loss, including occasional fatal injuries. Following high-profile injury deaths in Australia, concerns are raised regarding the safety of sport participation. To understand the scale and scope of injury deaths, and identify potential prevention opportunities, the aim of this investigation was to describe the number and nature of fatal injuries in Australian sport and recreation. METHODS: This is a retrospective cohort study of injury deaths reported between 1 July 2000 to 31 December 2019 using data from the National Coronial Information System, Australia. Unintentional deaths with an external cause, where the activity was recorded as sport and exercise during leisure time were included. Drowning deaths were excluded. Presented are the number and % of cases by age, sex, sport, broad cause and annual crude death rate (population). RESULTS: There were 1192 deaths, averaging 63 per year. Deaths were mostly in males (84.4%), with the largest proportion in people aged 15-24 years (23.1%). Wheeled motor (26.9%) and non-motor (16.2%) sports accounted for the highest proportion of cases. The primary mechanism of death was most commonly blunt force (85.4%), followed by piercing/penetrating force (5.0%). The years 2001 and 2005 recorded the highest crude injury death rate (2001, n = 92, 0.47 per 100,000 population; 2005, n = 95, 0.47 per 100,000 population). CONCLUSIONS: On average, there is more than one injury death per week in a sport or recreation setting in Australia. Cases occurred in many sports and recreation activities, including those generally considered to be safe (e.g. individual athletic activities, team ball sports.) Detailed investigation of the coronial recommendations that are present within each case is now needed to understand and identify potential prevention opportunities.

Vertebral artery dissection in sport: Expert opinion of mechanisms and risk-reduction strategies.

Experiential knowledge was collated to improve understanding of the mechanism of vertebral artery dissection (VAD) and inform recommendations for risk-reduction strategies in sport. Fourteen experts from fields of neurology, forensic pathology, biomedical engineering, radiology, physiotherapy, and sport and exercise medicine participated in semi-structured interviews. Experts were asked to provide their hypothesised mechanism of VAD, and suggest strategies to reduce the risk of VAD in non-motorised sports. Experts agreed that there is no single mechanism of VAD. Factors relating to predisposition, susceptibility, and an inciting event exist on a spectrum, as does the severity of the resulting VAD. Particularly concerning inciting events which may occur during sports participation include blunt force impact to the specific area behind and below the ear; and extreme movement of the neck, which may be facilitated by impact to the head or neck. Risk reduction strategies must be feasible within the particular sporting context. Strategies include rules, personal protective equipment, and education to reduce the risk of impact to the head or neck. Education may also serve to improve early recognition of VAD. VAD is a risk (low frequency, severe consequence) in sports in which athletes are exposed to head or neck impact from an object or opponent. Best practice risk management suggests that sports governing bodies should assess VAD risk and consider risk controls.

An assessment of the utility and functionality of wearable head impact sensors in Australian Football.

OBJECTIVES: To assess the utility and functionality of the X-Patch® as a measurement tool to study head impact exposure in Australian Football. Accuracy, precision, reliability and validity were examined. DESIGNS: Laboratory tests and prospective observational study. METHODS: Laboratory tests on X-Patch® were undertaken using an instrumented Hybrid III head and neck and linear impactor. Differences between X-Patch® and reference data were analysed. Australian Football players wore the X-Patch® devices and games were video-recorded. Video recordings were analysed qualitatively for head impact events and these were correlated with X-Patch® head acceleration events. Wearability of the X-Patch® was assessed using the Comfort Rating Scale for Wearable Computers. RESULTS: Laboratory head impacts, performed at multiple impact sites and velocities, identified significant correlations between headform-measured and device-measured kinematic parameters (p<0.05 for all). On average, the X-Patch®-recorded peak linear acceleration (PLA) was 17% greater than the reference PLA, 28% less for peak rotational acceleration (PRA) and 101% greater for the Head Injury Criterion (HIC). For video analysis, 118 head acceleration events (HAE) were included with PLA ≥30g across 53 players. Video recordings of X-Patch®-measured HAEs (PLA ≥30g) determined that 31.4% were direct head impacts, 9.3% were indirect impacts, 44.1% were unknown or unclear and 15.3% were neither direct nor indirect head impacts. The X-Patch® system was deemed wearable by 95-100% of respondents. CONCLUSIONS: This study reinforces evidence that use of the current X-Patch® devices should be limited to research only and in conjunction with video analysis.

Verifying Head Impacts Recorded by a Wearable Sensor using Video Footage in Rugby League: a Preliminary Study.

BACKGROUND: Rugby league is a full-contact collision sport with an inherent risk of concussion. Wearable instrumented technology was used to observe and characterize the level of exposure to head impacts during game play. PURPOSE: To verify the impacts recorded by the x-patch™ with video analysis. STUDY DESIGN: Observational case series. METHODS: The x-patch™ was used on eight men's semi-professional rugby league players during the 2016 Newcastle Rugby League competition (five forwards and three backs). Game day footage was recorded by a trained videographer using a single camera located at the highest midfield location to verify the impact recorded by the x-patch™. Videographic and accelerometer data were time synchronized. RESULTS: The x-patch™ sensors recorded a total of 779 impacts ≥ 20 g during the games, of which 732 (94.0%) were verified on video. In addition, 817 impacts were identified on video that did not record an impact on the sensors. The number of video-verified impacts ≥ 20 g, per playing hour, was 7.8 for forwards and 4.8 for backs (range = 3.9-19.0). Impacts resulting in a diagnosed concussion had much greater peak linear acceleration (M = 76.1 g, SD = 17.0) than impacts that did not result in a concussion (M = 34.2g, SD = 18.0; Cohen's d = 2.4). CONCLUSIONS: The vast majority (94%) of impacts ≥ 20 g captured by the x-patch™ sensor were video verified in semi-professional rugby league games. The use of a secondary source of information to verify impact events recorded by wearable sensors is beneficial in clarifying game events and exposure levels.

Vertebral Artery Dissection in Sport: A Systematic Review.

BACKGROUND: Vertebral artery dissection (VAD) is a potentially catastrophic injury that may occur during sports participation. A comprehensive review is needed to collate documented cases to improve understanding and inform future preventative approaches. OBJECTIVE: This review aimed to understand the extent of VAD in sport and characterise trends suggestive of mechanisms of injury. METHODS: Electronic databases were searched using terms related to VAD and sport. Records were included if they described one or more cases of VAD attributed to sport. RESULTS: A total of 79 records described 128 individual cases of VAD in sport, of which 118 were confirmed by imaging or autopsy and included in analyses. Cases were attributed to 43 contact and non-contact sports. The median age of cases was 33 years (IQR 22-44), and 75% were male. There were 22 cases of fatal injury, of which ten involved an impact to the mastoid region and seven involved an impact to the head or neck. Non-fatal cases of VAD were attributed to impact to the head or neck (not mastoid region), movement or held position without impact, and in some cases no reported incident. CONCLUSIONS: VAD attributed to sports participation is uncommonly reported and the mechanisms are varied. Impact to the mastoid region is consistently implicated in fatal cases and should be the focus of injury prevention strategies in sport. Efforts may also be directed at improving the prognosis of cases with delayed presentation through clinical recognition and imaging. The review was registered on the international prospective register for systematic reviews ( http://www.crd.york.ac.uk/PROSPERO ) (CRD42018090543).

Evaluation of an In-Ear Sensor for Quantifying Head Impacts in Youth Soccer.

BACKGROUND: Wearable sensor systems have the potential to quantify head kinematic responses of head impacts in soccer. However, on-field use of sensors (eg, accelerometers) remains challenging, owing to poor coupling to the head and difficulties discriminating low-severity direct head impacts from inertial loading of the head from human movements, such as jumping and landing. PURPOSE: To test the validity of an in-ear sensor for quantifying head impacts in youth soccer. STUDY DESIGN: Descriptive laboratory study. METHODS: First, the sensor was mounted to a Hybrid III headform and impacted with a linear impactor or a soccer ball. Peak linear acceleration (PLA), peak rotational acceleration (PRA), and peak rotational velocity (PRV) were obtained from both systems; random and systematic errors were calculated with Hybrid III as reference. Then, 6 youth soccer players wore sensors and performed a structured training protocol, including heading and nonheading exercises; they also completed 2 regular soccer sessions. For each accelerative event recorded, PLA, PRA, and PRV outputs were compared with video recordings. Receiver operating characteristic curves were used to determine the sensor's discriminatory capacity in both on-field settings, establishing cutoff values for predicting outcomes. RESULTS: For the laboratory tests, the random error was 11% for PLA, 20% for PRA, and 5% for PRV; the systematic error was 11%, 19%, and 5%, respectively. For the structured training protocol, heading events resulted in higher absolute values (PLA = 15.6 g± 11.8 g) than nonheading events (PLA = 4.6 g± 1.2 g); the area under the curve was 0.98 for PLA. In regular training sessions, the area under the curve was >0.99 for PLA. A 9 g cutoff value yielded a positive predictive value of 100% in the structured training protocol versus 65% in the regular soccer sessions. CONCLUSION: The in-ear sensor displayed considerable random error and substantially overestimated head impact exposure. Despite the sensor's excellent on-field accuracy for discriminating headings from other accelerative events in youth soccer, absolute values must be interpreted with caution, and there is a need for secondary means of verification (eg, video analysis) in real-life settings. CLINICAL RELEVANCE: Wearable sensor systems can potentially provide valuable insights into head impact exposures in contact sports, but their limitations require careful consideration.

Manual Handling in Aged Care: Impact of Environment-related Interventions on Mobility.

The manual handling of people (MHP) is known to be associated with high incidence of musculoskeletal disorders for aged care staff. Environment-related MHP interventions, such as appropriate seated heights to aid sit-to-stand transfers, can reduce staff injury while improving the patient's mobility. Promoting patient mobility within the manual handling interaction is an endorsed MHP risk control intervention strategy. This article provides a narrative review of the types of MHP environmental controls that can improve mobility, as well as the extent to which these environmental controls are considered in MHP risk management and assessment tools. Although a range of possible environmental interventions exist, current tools only consider these in a limited manner. Development of an assessment tool that more comprehensively covers environmental strategies in MHP risk management could help reduce staff injury and improve resident mobility through auditing existing practices and guiding the design of new and refurbished aged care facilities.

Head impact velocities in FIS World Cup snowboarders and freestyle skiers: Do real-life impacts exceed helmet testing standards?

INTRODUCTION: Prior to the 2013-2014 season, the International Ski Federation (FIS) increased the helmet testing speed from a minimum requirement of 5.4 to 6.8 m/s for alpine downhill, super-G and giant slalom and for freestyle ski cross, but not for the other freestyle disciplines or snowboarding. Whether this increased testing speed reflects impact velocities in real head injury situations on snow is unclear. We therefore investigated the injury mechanisms and gross head impact biomechanics in four real head injury situations among World Cup (WC) snowboard and freestyle athletes and compared these with helmet homologation laboratory test requirements. The helmets in the four cases complied with at least European Standards (EN) 1077 (Class B) or American Society for Testing and Materials (ASTM) F2040. METHODS: We analysed four head injury videos from the FIS Injury Surveillance System throughout eight WC seasons (2006-2014) in detail. We used motion analysis software to digitize the helmet's trajectory and estimated the head's kinematics in two dimensions, including directly preimpact and postimpact. RESULTS: All four impacts were to the occiput. In the four cases, the normal-to-slope preimpact velocity ranged from 7.0(±SD 0.2) m/s to 10.5±0.5 m/s and the normal-to-slope velocity change ranged from 8.4±0.6 m/s to 11.7±0.7 m/s. The sagittal plane helmet angular velocity estimates indicated a large change in angular velocity (25.0±2.9 rad/s to 49.1±0.3 rad/s). CONCLUSION: The estimated normal-to-slope preimpact velocity was higher than the current strictest helmet testing rule of 6.8 m/s in all four cases.

A systematic review of prospective epidemiological research into injury and illness in Olympic combat sport.

BACKGROUND: Combat sports involve body contact through striking, kicking and/or throwing. They are anecdotally referred to as 'dangerous', yet long-term investigation into specific injury rates is yet to be explored. OBJECTIVE: To describe incidence and prevalence of injury and illness within Olympic combat sports and to investigate risk of bias of prospective injury and illness research within these sports. METHODS: We systematically searched literature published up until May 2016. We included prospective studies of injury/illness in elite combat athletes lasting more than 12 weeks. Risk of bias was assessed using a modified version of the Downs and Black checklist for methodological quality. Included studies were mapped to the Oxford Centre for Evidence-Based Medicine levels of evidence. RESULTS: Nine studies were included, and most (n=6) had moderate risk of bias. Studies provided level 1/2b evidence that the most frequently injured areas were the head/face (45.8%), wrist (12.0%) and lower back (7.8%) in boxing; the lower back (10.9%), shoulder (10.2%) and knee (9.7%) in judo; the fingers (22.8%) and thigh (9.1%) in taekwondo; and the knee (24.8%), shoulder (17.8%) and head/face (16.6%) in wrestling. Heterogeneity of injury severity classifications and inconsistencies inexposure measures prevented any direct comparisons of injury severity/incidence across combat sports. CONCLUSIONS: There is currently a lack of consensus in the collection of injury/illness data, limiting the development of prevention programmes for combat sport as a whole. However, sport-specific data that identify body areas with high injury frequency can provide direction to clinicians, enabling them to focus their attention on developing pathologies in these areas. In doing so, clinicians can enhance the practical elements of their role within the integrated combat sport performance team and assist in the regular update of surveillance records.

Reconstruction of head impacts in FIS World Cup alpine skiing.

INTRODUCTION: Prior to the 2013/2014 season, the International Ski Federation (FIS) increased the helmet testing speed from 5.4 to 6.8 m/s for alpine downhill, super-G and giant slalom. Whether this increased testing speed reflects head impact velocities in real head injury situations on snow is unclear. We therefore investigated the injury mechanisms and gross head impact biomechanics in seven real head injury situations among World Cup (WC) alpine skiers. METHODS: We analysed nine head impacts from seven head injury videos from the FIS Injury Surveillance System, throughout nine WC seasons (2006-2015) in detail. We used commercial video-based motion analysis software to estimate head impact kinematics in two dimensions, including directly preimpact and postimpact, from broadcast video. The sagittal plane angular movement of the head was also measured using angle measurement software. RESULTS: In seven of nine head impacts, the estimated normal to slope preimpact velocity was higher than the current FIS helmet rule of 6.8 m/s (mean 8.1 (±SD 0.6) m/s, range 1.9±0.8 to 12.1±0.4 m/s). The nine head impacts had a mean normal to slope velocity change of 9.3±1.0 m/s, range 5.2±1.1 to 13.5±1.3 m/s. There was a large change in sagittal plane angular velocity (mean 43.3±2.9 rad/s (range 21.2±1.5 to 64.2±3.0 rad/s)) during impact. CONCLUSION: The estimated normal to slope preimpact velocity was higher than the current FIS helmet rule of 6.8 m/s in seven of nine head impacts.

SCAT3 changes from baseline and associations with X2 Patch measured head acceleration in amateur Australian football players.

OBJECTIVES: To investigate changes from baseline on SCAT3 as a result of football game exposure, and association with X2 Patch measured head acceleration events in amateur Australian footballers. DESIGN: Prospective cohort. METHODS: Peak linear acceleration (PLA) of the head (>10 g) was measured by wearable head acceleration sensor X2 Biosystems X-Patch in male (n=34) and female (n=19) Australian footballers. SCAT3 was administered at baseline (B) and post-game (PG). RESULTS: 1394 head acceleration events (HEA) >10 g were measured. Mean and median HEA PLA were recorded as 15.2 g (SD=9.2, range=10.0-115.8) and 12.4 g (IQR=11.0-15.6) respectively. No significant difference in median HEA PLA (g) was detected across gender (p=0.55), however, more HEAs were recorded in males (p=0.03). A greater number (p=0.004) and severity (p<0.001) of symptoms were reported PG than at B. No significant association between number of HEA or median PLA, and SCAT3 change scores (p>0.05 for all), was identified for either gender. CONCLUSIONS: Increase in symptom severity post game was not associated with X2 measured HEA. Males sustained more HEA, however HEA PLA magnitude did not differ across gender. Further work on the validation of head acceleration sensors is required and their role in sports concussion research and medical management.

Accelerometers for the Assessment of Concussion in Male Athletes: A Systematic Review and Meta-Analysis.

BACKGROUND: Concussion is common in the sporting arena and is often challenging to diagnose. The development of wearable head impact measurement systems has enabled measurement of head kinematics in contact sports. OBJECTIVES: The objective of this systematic review was to determine the characteristics of head kinematics measured by an accelerometer system among male athletes diagnosed with concussion. METHODS: A systematic search was conducted in July 2015. Inclusion criteria were English-language studies published after 1990 with a study population of male athletes, in any sport, where objectively measured biomechanical forces were reported in the setting of a concussive event. The random effects meta-analysis model was used to combine estimates of biomechanical force measurements in concussed athletes. RESULTS: Thirteen studies met the inclusion criteria, the majority of which were conducted with high school and college football teams in the US. Included studies measured a combination of linear and rotational acceleration. The meta-analysed mean peak linear head acceleration associated with a concussive episode was 98.68 g (95 % CI 82.36-115.00) and mean peak rotational head acceleration was 5776.60 rads/s2 (95 % CI 4583.53-6969.67). The estimates of the biomechanical forces were consistent across studies, with I 2 values of 0 % for both meta-analyses. CONCLUSIONS: Head impact monitoring through accelerometery has been shown to be useful with regard to characterising the kinematic load to the head associated with concussion. Future research with improved clinical outcome measures and head kinematic data may improve accuracy when evaluating concussion, and may assist with both interpretation of biomechanical data and the development and utilisation of implementation strategies for the technology.

Quantifying prosthetic gait deviation using simple outcome measures.

AIM: To develop a subset of simple outcome measures to quantify prosthetic gait deviation without needing three-dimensional gait analysis (3DGA). METHODS: Eight unilateral, transfemoral amputees and 12 unilateral, transtibial amputees were recruited. Twenty-eight able-bodied controls were recruited. All participants underwent 3DGA, the timed-up-and-go test and the six-minute walk test (6MWT). The lower-limb amputees also completed the Prosthesis Evaluation Questionnaire. Results from 3DGA were summarised using the gait deviation index (GDI), which was subsequently regressed, using stepwise regression, against the other measures. RESULTS: Step-length (SL), self-selected walking speed (SSWS) and the distance walked during the 6MWT (6MWD) were significantly correlated with GDI. The 6MWD was the strongest, single predictor of the GDI, followed by SL and SSWS. The predictive ability of the regression equations were improved following inclusion of self-report data related to mobility and prosthetic utility. CONCLUSION: This study offers a practicable alternative to quantifying kinematic deviation without the need to conduct complete 3DGA.

Boxing headguard performance in punch machine tests.

BACKGROUND: The paper presents a novel laboratory method for assessing boxing headguard impact performance. The method is applied to examine the effects of headguards on head impact dynamics and injury risk. METHODS: A linear impactor was developed, and a range of impacts was delivered to an instrumented Hybrid III head and neck system both with and without an AIBA (Association Internationale de Boxe Amateur)-approved headguard. Impacts at selected speeds between 4.1 and 8.3 m/s were undertaken. The impactor mass was approximately 4 kg and an interface comprising a semirigid 'fist' with a glove was used. RESULTS: The peak contact forces were in the range 1.9-5.9 kN. Differences in head impact responses between the Top Ten AIBA-approved headguard and bare headform in the lateral and forehead tests were large and/or significant. In the 8.3 m/s fist-glove impacts, the mean peak resultant headform accelerations for bare headform tests was approximately 130 g compared with approximately 85 g in the forehead impacts. In the 6.85 m/s bare headform impacts, mean peak resultant angular head accelerations were in the range of 5200-5600 rad/s(2) and almost halved by the headguard. Linear and angular accelerations in 45° forehead and 60° jaw impacts were reduced by the headguard. CONCLUSIONS: The data support the opinion that current AIBA headguards can play an important role in reducing the risk of concussion and superficial injury in boxing competition and training.

The impact performance of headguards for combat sports.

BACKGROUND/AIM: To assess the impact energy attenuation performance of a range of headguards for combat sports. METHODS: Seven headguards worn during combat sport training or competition, including two Association Internationale de Boxe Amateur (AIBA)-approved boxing models, were tested using drop tests. An International Organization for Standardization (ISO) rigid headform was used with a 5.6 kg drop assembly mass. Tests were conducted against a flat rigid anvil both with and without a boxing glove section. The centre forehead and lateral headguard areas were tested. Peak headform acceleration was measured. Tests from a selection of drop heights and repeated tests on the same headguard were conducted. RESULTS: Headguard performance varied by test condition. For the 0.4 m rigid anvil tests, the best model headguard was the thickest producing an average peak headform acceleration over 5 tests of 48 g compared with 456 g for the worst model. The mean peak acceleration for the 0.4, 0.5 and 0.6 frontal and lateral rigid anvil impact tests was between 32% and 40% lower for the Top Ten boxing model compared with the Adidas boxing model. The headguard performance deterioration observed with repeat impact against the flat anvil was reduced for impacts against the glove section. The overall reduction in acceleration for the combination of glove and headguard in comparison to the headguard condition was in the range of 72-93% for 0.6 and 0.8 m drop tests. CONCLUSIONS: The impact tests show the benefits of performance testing in identifying differences between headguard models.

The Biomechanical Determinants of Concussion: Finite Element Simulations to Investigate Tissue-Level Predictors of Injury During Sporting Impacts to the Unprotected Head.

Biomechanical studies of concussions have progressed from qualitative observations of head impacts to physical and numerical reconstructions, direct impact measurements, and finite element analyses. Supplementary to a previous study, which investigated maximum principal strain, the current study used a detailed finite element head model to simulate unhelmeted concussion and no-injury head impacts and evaluate the effectiveness of various tissue-level brain injury predictors: strain rate, product of strain and strain rate, cumulative strain damage measure, von Mises stress, and intracranial pressure. Von Mises stress was found to be the most effective predictor of concussion. It was also found that the thalamus and corpus callosum were brain regions with strong associations with concussion. Tentative tolerance limits for tissue-level predictors were proposed in an attempt to broaden the understanding of unhelmeted concussions. For the thalamus, tolerance limits were proposed for a 50% likelihood of concussion: 2.24 kPa, 24.0 s-1, and 2.49 s-1 for von Mises stress, strain rate, and the product of strain and strain rate, respectively. For the corpus callosum, tolerance limits were proposed for a 50% likelihood of concussion: 3.51 kPa, 25.1 s-1, and 2.76 s-1 for von Mises stress, strain rate, and the product of strain and strain rate, respectively.

Factors affecting motorcycle helmet use: size selection, stability, and position.

OBJECTIVES: One of the main requirements of a protective helmet is to provide and maintain appropriate and adequate coverage to the head. A helmet that is poorly fitted or fastened may become displaced during normal use or even ejected during a crash. METHODS: Observations and measurements of head dimensions, helmet position, adjustment, and stability were made on 216 motorcyclists. Helmet details were recorded. Participants completed a questionnaire on helmet usability and their riding history. Helmet stability was assessed quasistatically. RESULTS: Differences between the dimensions of ISO headforms and equivalent sized motorcyclists' heads were observed, especially head width. Almost all (94%) of the helmets were labeled to be compliant with AS/NZS 1698 (2006). The majority of riders were satisfied with the comfort, fit, and usability aspects of their helmets. The majority of helmets were deemed to have been worn correctly. Using quasistatic pull tests, it was found that helmet type (open-face or full-face) and the wearing correctness were among factors that affected the loads at which helmets became displaced. The forces required to displace the helmet were low, around 25 N. CONCLUSIONS: The size of the in-use motorcycle helmets did not correspond well to the predicted size based on head dimensions, although motorcyclists were generally satisfied with comfort and fit. The in vivo stability tests appear to overpredict that helmets will come off in a crash, based on the measured forces, tangential forces measured in the oblique impact tests, and the actual rate of helmet ejection.