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Present polo helmet testing methods only assess linear acceleration, neglecting the evaluation of a helmet's ability to reduce rotational acceleration. Both linear and rotational accelerations are key predictors of brain injuries. Therefore, understanding these measures is crucial for gauging the risk associated with each helmet. This report describes the results of a test series requested by the United States Polo Association Safety Committee that evaluated current polo helmets under rotational loading conditions.

This document details the protocol used by the Virginia Tech Helmet Ratings to rate snow sport helmets based on concussion risk.

When football originated in the 1800s, players wore no protective equipment. Between 1869 and 1905, there were 18 deaths and 159 serious injuries attributed to the sport. Following this, players began to wear protective equipment. The first use of a football helmet was in 1893, made of leather and designed to reduce the risk of skull fracture. Initially, football helmets were intended to protect a player against the most severe hits they would experience on the field. More recently, it has been shown that mild traumatic brain injuries, such as concussions, can induce long-term neurodegenerative processes. Since their introduction, helmets have transformed into plastic shells with padding designed to mitigate accelerations on the brain. With the growing concern for player safety, regulating bodies, like the National Operating Committee on Standards for Athletic Equipment, have implemented standards for protective equipment, including football helmets. On top of these standards, there have been multiple methods developed to assess helmet performance with different testing apparatuses. Manufacturers are interested in how their helmet performs according to multiple testing methods. This could be costly if they do not have the proper testing equipment that a protocol utilizes. This thesis assesses the interchangeability of different test equipment to reproduce a testing protocol. The desire to perform well in testing standards has driven the improvement of helmet performance and continued design innovation. The second aim of this thesis is to evaluate helmet performance and its relationship with design changes in football helmets manufactured between 1980 and 2018.

More than 19 million children participate in youth baseball and softball annually. Although baseball and softball are not commonly depicted as contact sports in the, according to the U.S. CPSC baseball and softball were responsible for 11.6% of all head injuries treated in emergency rooms in 2009; third most behind only cycling and football. Ball impact has been identified as the leading cause of injury in baseball and softball, with the most frequent injury resulting from a ball impacting the head. Reduced injury factor balls, infield softball masks, batter's helmets, and catcher's masks have all been integrated into baseball and softball as a means for preventing serious head injury from ball impact. The research in this thesis had four objectives: to compare the responses of the Hybrid III and NOCSAE headforms during high velocity projectile impacts, to compare head injury risk across a range of baseball stiffness designed for different age groups, to evaluate the effectiveness of infielder softball masks' ability to attenuate facial fracture risk, and to describe a novel methodology to evaluate the performance of batter's helmets and catcher's masks. Results of these research objectives determined the most suitable ATD headform to evaluate head injury risk for high velocity projectile impacts, provided a framework for determining the optimal age-specific ball stiffness and optimal infield mask design, and disseminated STAR ratings for batter's helmets and catcher's masks to the public. The research presented in this thesis can be used to further improve safety in baseball and softball.

Fit is often pointed to as the most important factor to consider when selecting a helmet. However, there is no published biomechanical evidence suggesting that of helmet fit effects concussion risk. The objectives of this study were to quantify helmet fit on a headform and to determine the effect fit has on helmet performance. An impact pendulum was used to strike a helmeted NOCSAE headform mounted on a Hybrid III neck. Helmets were impacted at 4 locations at 3 energies representing a range of concussive to sub-concussive impacts. The fit conditions evaluated in this study represent fitting scenarios in which an athlete is provided a helmet that is properly or improperly sized and cases in which a properly sized helmet is too loose, too tight, or properly adjusted. A custom pressure sensor was developed and used to characterize helmet fit in each condition with a quantitative fit metric representative of a variation from zero pressure on the headform. All helmets produced significant differences in both peak linear and peak angular acceleration due to fit. Differences were generally small with some exceptions. Furthermore, air bladder inflation generated significant differences in both peak linear and peak angular acceleration, but these were generally small in magnitude. While fit associated with size and air bladder inflation significantly affected linear and rotational head acceleration for most impact conditions, the best fit condition did not always generate the lowest accelerations. Differences can be attributed to varying helmet characteristics between and within helmet models.