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Mixed martial arts (MMA) is a sport where the fighters are at high risk of brain trauma, with characteristics, such as the frequency, magnitude, and interval of head impacts influencing the risk of developing short- and long-term negative brain health outcomes. These characteristics may be influenced by weight class as they may have unique fighting styles. The purpose of this research was to compare frequency, magnitude, and interval of head impacts between lightweight and heavyweight fighters in professional MMA. Frequency, interval, event type, velocity, and location of head impacts were documented for 60 fighters from 15 Lightweight and 15 Heavyweight professional MMA fights. Head impact reconstructions of these events were performed using physical and finite element modelling methods to determine the strain in the brain tissues. The results found that LW and HW fighters sustained similar head impact frequencies and intervals. The LW fighters sustained a significantly higher frequency of very low and high magnitude impacts to the head from punches; HW a larger frequency of high category strains from elbow strikes. These brain trauma profiles reflect different fight strategies and may inform methods to manage and mitigate the long-term effects of repetitive impacts to the head.

Rugby league has been identified as a contact sport with a high incidence of concussion. Research has been conducted to describe incidence and mechanisms of concussion in rugby league, however the risks associated with injury events (shoulder, hip, head to head) are unknown. The purpose of this study was to describe the common injury events leading to concussion in the National Rugby League and compare these events through analysis of dynamic response and brain tissue deformation. Twenty-seven impact videos of concussive injuries were physically reconstructed to obtain linear and rotational accelerations of the head. Dynamic response data were input into the University College Dublin Brain Trauma Model (UCDBTM) to calculate maximum principal strain (MPS). Head-to-head events produced a short duration event with an average peak linear and peak rotational acceleration of 205 g and 15,890 rad/s2, respectively, which were significantly greater than the longer duration hip-to-head (24.7 g and 2650 rad/s2) and shoulder-to-head (24.2 g and 3280 rad/s2) impacts. There were no differences in MPS between events. These results suggest that risk of strain to the brain may be produced by short and long duration acceleration events. Thus, both of these accelerations need to be accounted for in the development of improved head and body protection in rugby. In addition, this data demonstrates that these events cause a risk of concussion requiring efforts to limit or modify how energy is transferred to the head.

Compared to adults, it has been documented that children are at elevated risk for concussion, repeated concussions, and experience longer recovery times. What is unknown, is whether the developing brain may be injured at differing strain levels. This study examined peak and cumulative brain strain from 20 cases of concussion in both young children and adults using physical reconstructions and finite element modelling of the brain response to impacts. The child group showed lower impact kinematics as well as strain metrics. Results suggest children may suffer concussive injuries with lower brain strains compared to adults.

Objective Impacts to the head are the primary cause of concussive injuries in sport and can occur in a multitude of different environments. Each event is composed of combinations of impact characteristics (striking velocity, impact mass, and surface compliance) that present unique loading conditions on the head and brain. The purpose of this study was to compare falls, collisions, and punches from accident reconstructions of sports-related head impacts using linear, rotational accelerations and maximal principal strain of brain tissue from finite element simulation. Methods This study compared four types of head impact events through reconstruction. Seventy-two head impacts were taken from medical reports of accidental falls and game video of ice hockey, American football, and mixed-martial arts. These were reconstructed using physical impact systems to represent helmeted and unhelmeted falls, player-to-player collisions, and punches to the head. Head accelerations were collected using a Hybrid III headform and were input into a finite element brain model used to approximate strain in the cerebrum associated with the external loading conditions. Results Significant differences ( p 2) and pulse durations between all impact event types characterized by unique impact parameters. The only exception was found where punch impacts and helmeted falls had similar rotational durations. Regression analysis demonstrated that increases to strain from unhelmeted falls were significantly influenced by both linear and rotational accelerations, meanwhile helmeted falls, punches, and collisions were influenced by rotational accelerations alone. Conclusion This report illustrates that the four distinct impact events created unique peak head kinematics and brain tissue strain values. These distinct patterns of head acceleration characteristics suggest that it is important to keep in mind that head injury can occur from a range of low to high acceleration magnitudes and that impact parameters (surface compliance, striking velocity, and impact mass) play an important role on the duration-dependent tolerance to impact loading.

Despite young children being a high-risk population for sustaining concussive injuries in sport, few studies have investigated head impact biomechanics from sporting impacts using physical models and finite element models of the brain. Physical reconstructions are often used in concussive research, using the recorded kinematics to load finite element models of the brain to obtain better information of real-life head injuries. For children, scaling adult models is a common method used to study the youth population. However, this method does not capture age-dependent material properties or the unique geometry of the developing brain. To address these deficiencies, a novel three-dimensional finite element model of a 6-year-old child was developed and compared to a scaled adult model, for use with physical reconstructions. With the lack of intracranial validation data for the youth population, adult cadaveric data for brain motion was used for comparison. The new brain model showed unique responses in motion and strain compared to the scaled adult model. Using the normalized integral square error method, the new model was classified to have ‘fair’ to ‘excellent’ biofidelity. The new model is proposed as more appropriate for conducting concussion and brain injury research in young children near 6 years of age.

American football players are frequently exposed to head impacts, which can cause concussions and may lead to neurodegenerative diseases such as chronic traumatic encephalopathy (CTE). Player position appears to influence the risk of concussion but there is limited work on its effect on the risk of CTE. Computational modelling has shown that large brain deformations during head impacts co-localise with CTE pathology in sulci. Here we test whether player position has an effect on brain deformation within the sulci, a possible biomechanical trigger for CTE. We physically reconstructed 148 head impact events from video footage of American Football games. Players were separated into 3 different position profiles based on the magnitude and frequency of impacts. A detailed finite element model of TBI was then used to predict Green-Lagrange strain and strain rate across the brain and in sulci. Using a one-way ANOVA, we found that in positions where players were exposed to large magnitude and low frequency impacts (e.g. defensive back and wide receiver), strain and strain rate across the brain and in sulci were highest. We also found that rotational head motion is a key determinant in producing large strains and strain rates in the sulci. Our results suggest that player position has a significant effect on impact kinematics, influencing the magnitude of deformations within sulci, which spatially corresponds to where CTE pathology is observed. This work can inform future studies investigating different player-position risks for concussion and CTE and guide design of prevention systems.

Brain injuries are prevalent in the sport of American football. Helmets have been used which effectively have reduced the incidence of traumatic brain injury, but have had a limited effect on concussion rates. In an effort to improve the protective capacity of American football helmets, a standard has been proposed by National Operating Committee on Standards for Athletic Equipment that may better represent helmet-to-helmet impacts common to football concussions. The purpose of this research was to examine the National Operating Committee on Standards for Athletic Equipment standard and a new impact method similar to the proposed National Operating Committee on Standards for Athletic Equipment standard to examine the information these methods provide on helmet performance. Five National Operating Committee on Standards for Athletic Equipment–certified American football helmets were impacted according to the National Operating Committee on Standards for Athletic Equipment standard test and a new method based on the proposed standard test. The results demonstrated that the National Operating Committee on Standards for Athletic Equipment test produced larger linear accelerations than the new method, which were a reflection of the stiffer compliance of the standard meant to replicate traumatic brain injury mechanisms of injury. When the helmets were impacted using a new helmet-to-helmet method, the results reflected significant risk of concussive injury but showed differences in rotational acceleration responses between different helmet models. This suggests that the new system is sensitive enough to detect the effect of different design changes on rotational acceleration, a metric more closely associated with risk of concussion. As only one helmet produced magnitudes of response lower than the National Operating Committee on Standards for Athletic Equipment pass/fail using the new system, and all helmets passed the National Operating Committee on Standards for Athletic Equipment standard, these results suggest that further development of helmet technologies must be undertaken to reduce this risk in the future. Finally, these results show that it would be prudent to use both standards together to address risk of injury from traumatic brain injury and concussion.

Objective Like many sports involving high speeds and body contact, head injuries are a concern for short track speed skating athletes and coaches. While the mandatory use of helmets has managed to nearly eliminate catastrophic head injuries such as skull fractures and cerebral haemorrhages, they may not be as effective at reducing the risk of a concussion. The purpose of this study was to evaluate the performance characteristics of speed skating helmets with respect to managing peak linear and peak rotational acceleration, and to compare their performance against other types of helmets commonly worn within the speed skating sport. Materials and methods Commercially available speed skating, bicycle and ice hockey helmets were evaluated using a three-impact condition test protocol at an impact velocity of 4 m/s. Results and discussion Two speed skating helmet models yielded mean peak linear accelerations at a low-estimated probability range for sustaining a concussion for all three impact conditions. Conversely, the resulting mean peak rotational acceleration values were all found close to the high end of a probability range for sustaining a concussion. A similar tendency was observed for the bicycle and ice hockey helmets under the same impact conditions. Conclusion Speed skating helmets may not be as effective at managing rotational acceleration and therefore may not successfully protect the user against risks associated with concussion injuries.

Reconstruction of real-life events can be used to investigate the relationship between the mechanical parameters of the impact and concussion risk. Striking mass has typically been approximated as being the mass of the body part coming into contact with the head without accounting for the force applied by the striking athlete. Thus, the purpose of this study was to measure the effective impact mass of three common striking techniques in ice hockey. Fifteen participants were instructed to strike a suspended 50th percentile Hybrid III headform at least three times with their elbow or shoulder. Effective impact mass was calculated by measuring the change in velocity of the player and the headform. Mean effective impact mass for the extended elbow, tucked-in elbow, and shoulder check conditions were 4.8, 3.0, and 12.9 kg, respectively. Peak linear accelerations were lower than the values associated with concussion in American football which could be a reflection of the methodology used in this study as well as inherent differences between both sports.

Head injuries, and concussion in particular, have become a source of interest in the sport of ice hockey. This study proposes a monorail test methodology combined with a finite element method to evaluate ice hockey helmets in a centric/non-centric protocol with performance metrics more closely associated with risk of concussion. Two conditions were tested using the protocol: (a) helmeted versus no helmet, and (b) vinyl nitrile lined hockey helmet versus expanded polypropylene lined hockey helmet. The results indicate that the impact velocities and locations produced distinct responses. Also, the protocol distinguished important design characteristics of the two helmet liner types, with the vinyl nitrile lined helmet producing lower strain responses in the cerebrum. Furthermore, it was discovered that low risk of injury peak linear and rotational acceleration values can combine to produce much higher risks of injury when using brain deformation metrics. In conclusion, the use of finite element modeling of the human brain along with a centric/non-centric protocol provides an opportunity for researchers and helmet developers to observe how the dynamic response produced by these impacts influences brain tissue deformation and injury risk. This type of centric/non-centric physical to finite element modeling methodology could be used to guide innovation for new methods to prevent concussion. Deposited by bulk import

When determining head injury risks through event reconstruction, it is important to understand how individual impact characteristics influence the dynamic response of the head and its internal structures. The effect of impactor mass has not yet been analyzed in the literature. The purpose of this study was to determine the effects of impactor mass on the dynamic impact response and brain tissue deformation. A 50th-percentile Hybrid III adult male head form was impacted using a simple pendulum system. Impacts to a centric and a non-centric impact location were performed with six varied impactor masses at a velocity of 4.0 m/s. The peak linear and peak angular accelerations were measured. A finite element model (University College Dublin Brain Trauma Model) was used to determine brain deformation, namely, peak maximum principal strain and peak von Mises stress. Impactor mass produced significant differences for peak linear acceleration for centric (F5,24 = 217.55, p = 0.0005) and non-centric (F5,24 = 161.98, p = 0.0005) impact locations, and for peak angular acceleration for centric (F5,24 = 52.51, p = 0.0005) and non-centric (F5,24 = 4.18, p = 0.007) impact locations. A change in impactor mass also had a significant effect on the peak maximum principal strain for centric (F5,24 = 11.04, p = 0.0005) and non-centric (F5,24 = 5.87, p = 0.001) impact locations, and for peak von Mises stress for centric (F5,24 = 24.01, p = 0.0005) and non-centric (F5,24 = 4.62, p = 0.004) impact locations. These results confirm that the impactor mass of an impact should be considered when determining risks and prevention of head and brain injury. Deposited by bulk import

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. Deposited by bulk import 02/10/13 RB

Helmeted and unhelmeted impacts of Hybrid III 6-year-old and 50th percentile adult head forms were conducted to assess performance of helmets at characteristic falling conditions at three impact sites. The child head form was impacted at 3.3 m/s, and the adult at 5.5 m/s. The child helmet reduced linear and rotational acceleration by 64% and 62%, compared to the adult helmet which reduced levels by 48% and 50% respectively. The child helmet performed well under lower impact velocity conditions than those tested by helmet certification standards, it is hypothesized the soft comfort foam is responsible for this performance.