No description available.

Horse riding is a popular global activity involving a wide range of sporting events including dressage, endurance riding, eventing, show jumping, horse racing and rodeo. Unfortunately, horse riding and equestrian sporting events, report a high prevalence of concussion. The most common mechanism for brain injury in equestrian events involve high levels of linear and rotational acceleration during head impacts when falling from a horse. These accelerations create injurious brain tissue strain. While both linear and rotational accelerations occur during head impacts, the rotational components of acceleration are closely linked to brain tissue strain. To reduce brain strain, helmet technologies have been developed with the aim to reduce head rotational accelerations during an impact. The most common rotational managing technology, multi-directional impact protection system (MIPS), employs a low friction layer to reduce the amount of rotational acceleration sustained by the brain during head impacts. MIPS tests equestrian helmets using a monorail drop rig with a 45-degree steel anvil covered in 80 grit sandpaper at 6.2 m/s. The surface experiencing impact in the MIPS test method is a very low compliant surface (steel). It is impacted at a velocity of 6 m/s, and an anvil angle of 45-degrees. In contrast, most impacts in equestrian involve high compliant material such as sand or turf with an average impact velocity is 9 m/s, and the average angle of impact of 27 degrees. The proposed rotational testing method employed by MIPS may not fully represent the most common accidents involving equestrian events. The objective of this research was to evaluate the effectiveness of a helmet with rotational technology to reduce linear and rotational acceleration, rotational velocity, and maximum principal strain (MPS) in equestrian helmets. An equestrian specific test protocol was developed using the common impact conditions for concussive events for equestrian riders. Nine m/s impact velocity, with an angle of 26.5 degrees to the horizontal axis, and an anvil compliance consisting of 66 mm of 602 vinyl nitrile foam with synthetic grass to represent turf impacts was reported as the most common impact characteristics. Using a Rail Guided Launcher, a helmeted Hybrid III headform was launched and impacted a low and high compliance anvil using the defined velocity and angle parameters. Two equestrian helmet types were impacted, a conventional helmet with no rotational technology and the same helmet model with rotational technology. The impact locations tested included front, side, and rear boss, as these were the most common impact locations reported for concussive events in equestrian. Linear and rotational acceleration and rotational velocity were measured using a DTS SLICE sensor installed inside the headform. The linear and rotational acceleration curves were then used as input to the University College Dublin Brain Trauma Model (V2.0) to calculate MPS. Statistical analysis included four t-tests, two 2x2x3 ANOVA's with 8 pairwise Tukey post-hoc test, significance set to α=0.05. The results were not uniform across impact locations and anvil compliances, the rear boss impact location in helmets with rotational technology revealed significantly lower rotational accelerations and rotational velocity. The results revealed helmets with rotational technology should be designed to perform under these high-energy conditions. If the rotational technology was designed with these considerations, it would be possible to investigate the potential of rotational technologies to decrease dynamic head response and the brain tissue strain.

The studies presented in this dissertation investigated biomechanical factors associated with sports-related brain injuries on the field and in the laboratory. In the first study, head impact exposure in youth football was observed using a helmet mounted accelerometer system to measure head kinematics. The results suggest that restriction on contact in practice at the youth level can translate into reduced head impact exposure over the course of a season. A second study investigated the effect of measurement error in the head impact kinematic data collected by the helmet mounted system have on subsequent analyses. The objective of this study was to characterize the propagation of random measurement error through data analyses by quantifying descriptive statistic uncertainties and biases for biomechanical datasets with random measurement error. For distribution analyses, uncertainties tend to decrease as sample sizes grow such that for a typical player, the uncertainties would be around 5% for peak linear acceleration and 10% for peak angular (rotational) acceleration. The third and fourth studies looked at comparisons between two headforms commonly used in athletic helmet testing, the Hybrid III and NOCSAE headforms. One study compared the headform shape, particularly looking at regions that are likely to affect helmet fit. Major differences were found at the nape of the neck and in the check/jaw regions that may contribute to difficulty with fitting a helmet to the Hybrid III headform. For the final study, the impact responses of the two headforms were compared. Both headforms were mounted on a Hybrid III neck and impacted at various magnitudes and locations that are representative of impacts observed on the football field. Some condition-specific differences in kinematic parameters were found between the two headforms though they tended to be small. Both headforms showed reasonable repeatability. / Ph. D.

Recent applications of medical imaging, advanced polymers, and composites have led to the development of new equipment for athletes and soldiers. A desire to understand the performance of headgear that resists impacts ongoing since the 1970’s has found more traction in recent years with the usage experimental models that have a greater degree of bio-fidelity. In order to determine which features of helmets from different sports (Soccer, Lacrosse, Football, and Hockey) were tested on a Hybrid III 50th Percentile Male headform with an accelerometer rig at the center of mass.Testing was performed by administering impacts to the headform with an impulse hammer that provides transient force data in order to quantify inputs and outputs of the system to develop a non-dimensional transfer function. Helmet performance is compared by sport worn in order to determine desirable manufacturing features and develop prototype helmets that outperforms current athletic equipment.

Preservation and protection of the head segment is of upmost importance due to the criticality of the functions entailed in this section of the body by the brain and the nervous system. Numerous events in daily life situations such as transportation and sports pose threats of injuries that may end or change a person’s life. In the European Union, statistics report that almost 4.2 million of road users are injured non-fatally, out of which 18% is represented by motorcyclist and 40% by cyclists, being head injuries 34% for bicyclists, and 24% for two-wheeled motor vehicles. Not only vehicles, are a source of injuries for the human head according to the injury report, 6,1 million people are admitted in hospitals for sports related injuries, where sports such as hockey, swimming, cycling presented head injuries up to 28%, 25% and 16% respectively (European Association for Injury Prevention and Safety Promotion, 2013).  According to records the vast majority of head crashes result in an oblique impact (Thibault & Gennarelli, 1985). These types of impacts are characterized for involving a rotation of the head segment which is correlated with serious head injuries. Even though there is plenty of evidence suggesting the involvement of rotational forces current helmet development standards and regulations fail to recognize their importance and account only for translational impact tests. This thesis contains an evaluation for a different developed method for testing oblique impacts. In consequence a new test rig was constructed with basis on a guided free fall of a helmeted dummy head striking an oblique (angled) anvil which will induce rotation. The results obtained are intended to be subjected to a comparison with another oblique test rig that performs experiments utilizing a movable sliding plate which when impacted induces the rotation of a dropped helmeted dummy head. The outcome will solidify the presence of rotational forces at head-anvil impact and offer an alternative testing method. After setting up the new test rig; experiments were conducted utilizing bicycle helmets varying the velocities before impact from 5m/s to 6m/s crashing an angled anvil of 45°. Results showed higher peak resultant values for rotational accelerations and rotational velocities in the new test rig compared to the movable plate impact test, indicating that depending on the impact situation the “Normal Force” has a direct effect on the rotational components. On the other hand a performed finite element analysis predicted that the best correlation between both methods is when the new angled anvil impact test is submitted to crashes with a velocity before impact of 6 m/s at 45° and the movable sliding impact test to a resultant velocity vector of 7,6m/s with an angle of 30° . In conclusion the new test method is meant to provide a comparison between two different test rigs that will undoubtedly have a part in the analysis for helmet and head safety improvements.