The primary purpose of this study was to determine the association between Apolipoprotein E (APOE) genotype and head impact response in high school athletes. The secondary purpose was to determine if quality of life (QoL) and cognitive functioning scores significantly differ between Apolipoprotein (APOE) rare allele carriers versus non-carriers within a poor head impact response (PHIR) group of high school athletes. Thirty (28 males, 2 females) high school athletes playing high head impact sports participated in the study. A between-subjects design was used. Primary aim one independent variable was genotype (i.e., APOE E4 carriers vs. non-carriers and APOE G-219T carriers vs. non-carriers) and dependent variable was group [i.e., normal head impact response (NHIR) vs. PHIR]. Statistical analysis consisted of Fisher's exact tests. Alpha level was set at p p p = .002) in the overall QoL scores between APOE G-219T promoter rare allele carriers versus non-carriers within the PHIR group. No other statistically significant differences were found; however, there was a trend (p = .007) found in the psychosocial subscores in the APOE G-219T promoter rare allele carriers versus non-carriers within the PHIR group. Carrying an APOE rare G-219T rare allele was associated with significantly lower QoL scores within the PHIR group, these results indicate that athletes with intrinsic (e.g., genotype) risk factors may need more education and different treatment following head impacts. / Kinesiology

Post-concussion syndrome (PCS) is a poorly understood sequela of mild traumatic brain injury (mTBI), more commonly referred to as concussion. While PCS is known to affect a subset of individuals following injury, it remains unclear how and why specific individuals incur chronic symptoms. Concussions disrupt normal neurophysiologic function within the brain, however the neurophysiologic underpinnings of PCS are unclear. Using transcranial magnetic stimulation (TMS), it is possible to non-invasively investigate neurotransmission in clinical populations such as those with PCS by stimulating the primary motor cortex (M1) and recording motor outputs in a contralateral hand muscle. A study was conducted using TMS to measure corticospinal excitability, intracortical facilitation and inhibition, and transcallosal inhibition in M1 of a group with PCS and a non-injured, healthy control group. Greater corticospinal excitability, and specific reductions in intracortical and transcallosal inhibition were observed in the PCS group, providing evidence of impaired neurotransmitter receptor activity. Importantly, these findings differed from previous observations in recovered concussion groups using similar stimulation techniques. Furthermore, it was observed that these neurophysiological differences may relate specifically to the presence of depression symptoms rather than general concussion symptoms. The physiologic and clinical implications of the findings of this thesis are discussed, and novel research avenues warranting investigation are identified. / Thesis / Master of Science in Kinesiology

Background: Sleep is commonly disrupted following pediatric concussion. Recently, post-concussion sleep quality has been identified as a potential factor that may influence recovery length. However, few studies have examined this relationship using objective sleep measures in a pediatric population. Nor, have any studies examined the trajectory of objective sleep parameters after pediatric concussion. Objectives: The purpose of this thesis is to: 1) Provide a review of current literature regarding pediatric concussion, healthy sleep quality, and sleep quality in the context of concussion and recovery from concussion; 2) Examine how objective sleep outcomes are affected and change post-concussion in children and adolescents; 3). Explore how post-concussion sleep quality parameters are related to length of recovery, quality of life (QOL), and depression symptomatology; and 4) Discusses the results from the two studies in the context of current literature and of each other. Methods: Sleep quality was inferred from the outcomes of five objective sleep parameters. Sleep parameters were measured using actigraphy in children and adolescents with concussion following return to school (RTA) and return to activity (RTA) protocols. Sleep data during the initial 4 weeks of recovery was assessed as an outcome, as a predictor of recovery length, and as a correlate of quality of life (QOL) and depression symptomatology Results: Most objective post-concussion sleep quality parameters were adversely affected by concussion but show trajectories indicating improvement throughout the initial 4 weeks of recovery. Sleep quality parameters were not associated with time to complete return to school or activity protocols. Sleep parameters were not strongly correlated with QOL or depression symptomatology outcomes. Conclusions: These results indicate that objective post-concussion sleep quality is impaired following concussion, but these outcomes do not appear to be associated with recovery, QOL or depression symptomatology. Other factors, or improvements in sleep quality may better explain recovery outcomes. / Thesis / Master of Science (MSc) / Children and adolescents are at risk for experiencing changes in sleep following concussion that result in poor sleep quality. Given the important role of sleep in maintaining our overall health, sleep likely plays a role in recovery. However, this relationship is poorly understood. The purpose of this dissertation is to identify how sleep changes following concussion and how these changes affect sleep quality and recovery. Study results reveal that the sleep parameters in the initial 4 weeks following concussion are significantly affected by concussion, suggesting that the sleep quality of children and adolescents is poorer than healthy youth. However, sleep quality does appear to improve with time. Further analyses found sleep quality does not appear to be related to recovery length or outcomes. Thus, the sleep quality of youth may be negatively impacted by concussion, but this may not directly influence recovery.

Yes / This article discusses the current evidence for the short- and long-term effects of concussion in sport and how occurrences of concussion should be managed. The article also considers the potential role of medical imaging in terms of assessing both acute and chronic head injuries. Greater awareness of when medical imaging could be used will aid the practitioner's understanding of its potential contribution while still maintaining the fundamental importance of clinical judgement.

The research presented herein is an analysis of acceleration measurements of the head during helmet-helmet impacts, where a player's helmet impacts another player's helmet, and with a youth population in football. This research is aimed at advancing current understanding of impact biomechanics for two specialized groups. The first study is an observational analysis focusing on helmet-helmet impacts, and the difference in effective mass and head acceleration measurements between the striking player and the struck player. The study involved working with football players outfitted with a sensor integrated into their helmets containing a 6 accelerometer array, capable of measuring linear accelerations and estimating angular accelerations. To evaluate helmet-helmet impacts, video analysis of past NCAA football competitions between Virginia Tech and University of North Carolina (UNC) were utilized to identify these impacts between instrumented players. A force balance was then carried out for the observed impacts and their respective acceleration measurements to compute the effective mass of the players. It was determined that the total mass recruited by the striking player was 28% to 77% more than that of the struck player. The second study focused on documenting the head impact biomechanics of a youth population. To accomplish this objective, unique accelerometer arrays, capable of measuring linear and angular accelerations, were integrated into existing youth football helmets for 7 players on a local team. Acceleration data were collected for every practice and game during the 2011 season to amass a total of 748 impacts. No instrumented player sustained a concussion during the 2011 season. Results of the study indicated impacts of greater magnitudes were more likely to occur in practices, and can be minimized by augmenting practice activities. / Master of Science

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. / Master of Science / 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. Another aim of this thesis is to evaluate helmet performance and its relationship with design changes in football helmets manufactured between 1980 and 2018.

Concussions are diffuse injuries that affect areas of the brain responsible for a person's physical, cognitive, and emotional health. Although concussions were once thought only to present transient symptoms, mounting evidence suggests potential for long-term neurological impairments. The deleterious effects of concussion can be from a single, high severity impact event or the accumulation of lower severity impacts. Clinical changes that can result from concussion include an elevated symptom presentation and changes in gait, or an individual's walking pattern. It is not well understood if similar deficits result after an accumulation of subconcussive impacts. The majority of research on human tolerance to head injury has been based on American football, using helmet-mounted sensors in male athletes. Limited studies have attempted to quantify biomechanical tolerance in women, despite the sex-specific nature of presentation and outcome of concussion. Biomechanical, physiologic, and psychosocial factors differ between males and females, likely contributing to this difference. The research presented in this dissertation was aimed at describing sex-specific outcomes of subconcussion in a matched cohort of male and female athletes to gain a better sense of unhelmeted, sex-specific tolerance to head impacts. On-field data were collected from collegiate rugby players using instrumented mouthguards. Rugby involves high energy, frequent head impacts, does not require protective headgear, and is played the same for both men and women. The females in our study sustained fewer impacts per session than the males, but their impacts had similar linear acceleration magnitudes. The kinematics of the concussive male impacts were higher than the kinematics of the concussive female impacts. Both sexes reported concussion-like symptoms in the absence of diagnosed concussion during a season. Females reported more symptoms with a higher severity in-season compared to males after subconcussive and concussive impacts. Female athletes saw deficits in cadence, double support time, gait speed, and stride length post-concussion. The majority of athletes improved in their dual-task gait assessment by the end of the season, suggesting there may not be a negative effect on gait after an accumulation of subconcussive impacts. This work assessed the biomechanics of head impacts and concussions of this population, and evaluated changes in symptom presentation through weekly graded symptom surveys and dual-task gait assessments both after a concussion and as an effect of subconcussive impacts. Understanding the sex-specific clinical effects of head impacts is critical, and can provide insight into concussion diagnostic, management, and prevention tools that are appropriate and effective. / Doctor of Philosophy / Concussions are injuries that affect many areas of the brain, including those responsible for a person's physical, cognitive, and emotional health. Although concussions were once thought only to present transient symptoms, mounting evidence suggests potential for long-term neurological impairments. The harmful effects of concussion can be from a single, high intensity impact event or the build-up of lower intensity impacts. Clinical changes that can result from concussion include an elevated symptom presentation and changes in gait, or an individual's walking pattern. It is not well understood if similar side effects result after an accumulation of subconcussive impacts. The majority of research on human tolerance to head injury has been based on American football, using helmet-mounted sensors in male athletes. Limited studies have attempted to quantify concussion tolerance in women, despite the differences in men and women's symptoms and recovery time after a concussion. Female's neck strength, hormones, and increased honesty in reporting concussion differ from males, likely contributing to this difference. The research presented in this dissertation was aimed at describing how sex affects the results of subconcussion in a group of male and female athletes to gain a better sense of unhelmeted, sex-specific tolerance to head impacts. On-field data were collected from collegiate rugby players using sensor-embedded mouthguards. Rugby involves high energy, frequent head impacts, does not require protective headgear, and is played the same by both men and women. The females in our study sustained fewer impacts per session than the males, but their impacts were similar in magnitude. The impact energies of the concussive male impacts were higher than those of the concussive female impacts. Both sexes reported concussion-like symptoms in the absence of diagnosed concussion during a season. Females reported more symptoms with a higher severity in-season compared to males after subconcussive and concussive impacts. Female athletes had a slower walking pace and walking speed, a shorter stride length, and spent more time with both feet on the ground post-concussion. The majority of athletes improved in their dual-task gait assessment by the end of the season, suggesting there may not be a negative effect on gait after an accumulation of subconcussive impacts. This work assessed the biomechanics of head impacts and concussions of this population, and evaluated changes in symptom presentation through weekly graded symptom surveys and dual-task gait assessments both after a concussion and as an effect of subconcussive impacts. Understanding the sex-specific clinical effects of head impacts is critical, and can provide insight into concussion diagnostic, management, and prevention tools that are appropriate and effective.

Cycling is an increasingly popular mode of transportation and a preferred form of exercise worldwide. From 1990 to 2015, commuting via bicycle increased as much as four-fold in cities across North America and Europe. However, this increase in cycling is associated with an increase in cycling related fatalities and head injuries. The best way to prevent severe head injury while cycling is to wear a bike helmet. Bike helmets are designed to decrease the linear acceleration of the head, decreasing the rider's risk of severe head injuries, such as skull fracture. In order to sell a bike helmet, it must meet a minimum standard of protection based on linear acceleration of the head upon impact. However, bike helmet impacts are not completely linear in nature and experience a tangential component through angled impacts of the helmet, resulting in rotational accelerations and shear-strain at the skull-brain interface. This strain cause brain injuries such as concussion. Therefore, recent helmet advancements have aimed to decrease rotational acceleration of the head. To continue the advancement of helmet technology and the subsequent decrease of brain injury risk to riders, investigating the impact conditions of real-world impacts is pertinent. This thesis aimed to increase the current body of knowledge of cycling related head impacts. The first aim was to quantify real-world impact locations and analyze how impact location may influence helmet performance. The second aim of this thesis was to investigate the impact velocities and resulting kinematics of real-world crashes based on the magnitude of corresponding damage conditions. Additionally, this aim analyzed the impact conditions from cases which resulted in concussion. Together these studies aim to provide valuable real-world data to be used for the advancement of helmet technologies and design. / Master of Science / Cycling is an increasingly popular mode of transportation and a preferred form of exercise worldwide. From 1990 to 2015, commuting via bicycle increased as much as four-fold in cities across North America and Europe. However, this increase in cycling is associated with an increase in cycling related fatalities and head injuries. The best way to prevent severe head injury while cycling is to wear a bike helmet. Bike helmets are designed to decrease the linear acceleration of the head, decreasing the rider's risk of severe head injuries, such as skull fracture. In order to sell a bike helmet, it must meet a minimum standard of protection based on linear acceleration of the head upon impact. However, bike helmet impacts are not completely linear in nature and experience a tangential component through angled impacts of the helmet, resulting in rotational accelerations and shear-strain at the skull-brain interface. This strain cause brain injuries such as concussion. Therefore, recent helmet advancements have aimed to decrease rotational acceleration of the head. To continue the advancement of helmet technology and the subsequent decrease of brain injury risk to riders, investigating the impact conditions of real-world impacts is pertinent. This thesis aimed to increase the current body of knowledge of cycling related head impacts. The first aim was to quantify real-world impact locations and analyze how impact location may influence helmet performance. The second aim of this thesis was to investigate the impact velocities and resulting kinematics of real-world crashes based on the magnitude of corresponding damage conditions. Additionally, this aim analyzed the impact conditions from cases which resulted in concussion. Together these studies aim to provide valuable real-world data to be used for the advancement of helmet technologies and design.

The research presented in the thesis explores the biomechanics of the head and neck during impacts in football. The research related to the head is geared towards advancing the current understanding of the mechanisms of mild traumatic brain injury, specifically by investigating head accelerations experienced by football players during impacts. To do this, a six degree of freedom sensor that could be integrated into existing football helmets and is capable of measuring linear and angular acceleration about each axis of the head was developed and validated. This sensor was then installed in the helmets of 10 Virginia Tech football players and data was recorded for every game and practice during the 2007 football season. A total 1712 impacts were recorded, creating a large and unbiased dataset. No instrumented player sustained a concussion during the 2007 season. From 2007 head acceleration dataset, 24 of the most severe impacts were modeled using a finite element head model, SIMon (Simulated Injury Monitor). Besides looking at head acceleration, the force transmitted to the mandible by chin straps in football helmets was investigated through impact testing. Little research has been conducted looking at the mandible-chin strap interface in the helmet, and this may be an area of helmet design that can be improved. The research presented in this thesis related to the neck is based on stingers. Football players wear neck collars to prevent stingers; however, their designs are largely based on empirical data, with little biomechanical testing. The load limiting capabilities of various neck collars were investigated through dynamic impact testing with anthropomorphic test devices. It was found that reductions in loads correlate with the degree to which each collar restricted motion of the head and neck. To investigate the differences in results that using different anthropomorphic test devices may present, the matched neck collar tests were performed with the Hybrid III and THOR-NT 50th percentile male dummies. The dummies exhibited the same trends, in that either a load was reduced or increased; however, each load was affected to a different degree. / Master of Science

In recent years, concussions and the effect this injury has on the human brain has been an area of concern for many people involved in sports. And perhaps rightfully so, as between 1.6 and 3.8 million people each year sustain a sports-related concussion in the United States. In the past, concussions have been solely linked to transient symptoms; however, recent research suggests that the injury can also result in long term neurocognitive impairment. Thus, there is much needed research to better understand concussions and assist in the development of safety techniques that will reduce the occurrence of such injury. Participants of youth football are at an extreme disadvantage as very little research has been conducted on this population. The research presented in this dissertation attempts to characterize head impact exposure of a variable subgroup of youth football, middle school football, in order to better understand concussions in youth. In addition to better understanding concussions, it is imperative that correct laboratory techniques are developed to accurately simulate realistic head impacts. This dissertation also presents results from the evaluation of current testing procedures that can be used for laboratory testing of sports equipment and simulation of actual field impacts. Evaluation of these techniques will further validate their ability to act as methods for both safety and research in sports injury. Thus, the overall goal of this dissertation is to provide results that will both further understanding of concussions and evaluate the realistic performance of laboratory techniques, influencing informed decisions to reduce the risk of concussions. / Ph. D.