As many as 1.9 million sports-related concussions occur annually in youth sports in the United States (U.S.). Often considered a transient injury, research has begun to relate sports-related concussions to long-term neurodegeneration. Youth athletes are considered to be more vulnerable to concussion than their adult counterparts. The research presented in this dissertation was aimed at promoting player safety in youth football as it relates to concussion. Balance dysfunction is often cited as one of the most common symptoms associated with a concussion. Several postural control assessments were assessed in order to develop a youth-specific testing protocol. A cognitive, dual-task assessment was presented for clinician use in the management of sports-related concussion. On-field data collected from youth football players wearing instrumented helmets allowed for characterization of the biomechanics of head impacts and concussions for this population. A youth concussion risk function was developed using head impact data collected from youth football players with medically diagnosed concussions. The proposed testing standard for youth football helmets was assessed in the laboratory and related to on-field head impact data to determine how representative the standard is of youth football head impacts. Helmet safety standards and certifications operate on a pass-fail threshold that does not allow consumers to weigh the relative performance of helmets. A modification of the Summation of Tests for the Analysis of Risk (STAR) evaluation system was developed for youth football helmets. Data presented in this dissertation have direct application to the development of future helmet safety standards and potentially other safety applications as well. / Doctor of Philosophy / As many as 1.9 million sports-related concussions occur annually in youth sports in the United States (U.S.). Often considered a short-term injury, research has begun to relate sports-related concussions to long-term breakdowns in neurological processes. Youth athletes are considered to be more vulnerable to concussion than their adult counterparts. The research presented in this dissertation was aimed at informing player safety in youth football as it relates to concussion. Abnormal balance is often cited as one of the most common symptoms associated with a concussion. Several balance assessments were assessed in order to develop a youth-specific testing protocol. An assessment involving quiet standing while being subjected to a cognitive task was presented for clinician use in the management of sports-related concussion. On-field data collected from youth football players wearing instrumented helmets allowed for characterization of the biomechanics of head impacts and concussions for this youth population. A youth concussion risk function was developed that related linear and rotational head acceleration to risk of concussion. The proposed testing standard for youth football helmets was assessed in the laboratory and observed to assess the most severe head impacts a youth player may experience during participation in football. A modification of the Summation of Tests for the Analysis of Risk (STAR) evaluation system was developed for youth football helmets in order to give consumers more information about helmet performance beyond the pass-fail criteria of the helmet standards. Data presented in this dissertation have direct application to the development of future helmet safety standards and potentially other safety applications as well.

Equines have been used for utilized for manual labor, recreation, and companionship amongst many other valuable conveniences since their domestication. As the modern horse progressed from livestock to athlete, attention was paid to the body conformation to be used as an indicator of biomechanics and can dictate equine performance. Poor conformation can put physical limitations on the body and predispose the horse to injury and chronic disease. When not managed properly, these flaws can lead to injury, lameness, and premature retirement in sport horses. The distal limb is composed of tendons and ligaments that are all susceptible to tear or rupture. Protective wraps or boots are typically applied to the distal limb prior to exercise to prevent superficial injury from the environment or interference. However, these preventatives can trap heat against the skin which can have detrimental effects on the fibroblasts which can lead to failure. It was not until the early twentieth century that the idea of equine physiotherapy was adopted, and practices changed to meet remedial needs and create a sustainable, healthy equine athlete. Equine physiotherapy is a broad-spectrum term used to describe the therapeutic efforts made to keep the body in good health by means of prevention of injury to improve or maintain performance. Traditionally, therapeutics are administered by a veterinarian or trained professional in the event of an existing injury. In recent years therapeutics have been commercialized and are readily available for everyday preventative use. The most common readily available treatments being variations of pulsating electromagnetic fields (PEMF), vibration therapy, cryotherapy, and thermotherapy. When used prior to or after exercise, the therapeutics are designed to prepare the body for exercise and improve recovery by increasing circulation and down regulating the inflammatory response. The studies performed evaluate the efficacy of Rambo®Ionic (Horseware, Dundalk,Ireland), Lux Ceramic Therapy® (Schneider Saddlery Co., Inc., Ohio, USA), and Ice-Vibe® (Horseware, Dundalk,Ireland) therapeutic boots when applied to the distal limb as per manufacturer recommendation. The first study evaluated the therapeutic boots ability to alter performance performing gait analysis using the ALOGO™ MovePro (Alogo Technologies, Switzerland) stride sensor, blood analysis measuring serum concentrations of C reactive protein (CRP), basic fibroblast growth factor (bFGF) and tenascin-C (TN-C), and capturing thermal images of the distal limb using an HT-19 thermal imaging camera (HTI, La Vergne, TN). In this study, eight healthy horses were exercised for approximately ten minutes per day for five consecutive days. There was a ten-day washout period where the horse received no treatment between each period; there was a total of four periods. The second study only evaluated Rambo®Ionic (Horseware, Dundalk,Ireland) and Ice-Vibe® (Horseware, Dundalk,Ireland) therapeutic boots on seventeen healthy horses in the Virginia Tech equitation lesson program. There were three periods with five days of consecutive data collection and a ten-day washout period in between where the horses received no treatment. Gait analysis was measured using the ALOGO™ MovePro (Alogo Technologies, Switzerland) stride sensor and a blind behavioral analysis was performed to analyze behavioral changes under saddle in response to a rider. / Master of Science / Equines have been used for utilized for manual labor, recreation, and companionship amongst many other valuable conveniences since their domestication. As the modern horse progressed from livestock to athlete, attention was paid to the structure of the horse, otherwise known as conformation. Conformation is an indicator of physical movement and can dictate what uses the horse is best suited for. In undesirable cases, poor conformation can put physical limitations on the body and predispose the horse to injury and chronic disease. When not managed properly, these flaws can lead to injury, lameness, and premature retirement in sport horses. The distal limb is a particularly vulnerable structure. It is free of muscle and is comprised of tendons, ligaments, and mobile joints. A protective wrap or boot is typically applied to the distal limb prior to exercise which can have detrimental effects on the cellular components of the associated structures which can lead to failure. It was not until the early twentieth century that the idea of equine physiotherapy was adopted, and practices changed to meet remedial needs and create a sustainable, healthy equine athlete. Equine physiotherapy is a broad-spectrum term used to describe the therapeutic efforts made to keep the body in good health by means of prevention of injury to improve or maintain performance. Traditionally, therapeutics are administered by a veterinarian or trained professional in the event of an existing injury. In recent years therapeutics have been commercialized and are readily available for everyday preventative use. The most common readily available treatments being variations of pulsating electromagnetic fields (PEMF), vibration therapy, cryotherapy, and thermotherapy. When used prior to or after exercise, the therapeutics are designed to prepare the body for exercise and improve recovery by increasing circulation and down regulating the inflammatory response. The studies performed evaluate the efficacy of Rambo®Ionic (Horseware, Dundalk,Ireland), Lux Ceramic Therapy® (Schneider Saddlery Co., Inc., Ohio, USA), and Ice-Vibe® (Horseware, Dundalk,Ireland) therapeutic boots when applied to the distal limb as per manufacturer recommendation. The first study evaluated the therapeutic boots ability to alter performance performing gait analysis using the ALOGO™ MovePro (Alogo Technologies, Switzerland) stride sensor, blood analysis measuring serum concentrations of C reactive protein (CRP), basic fibroblast growth factor (bFGF) and tenascin-C (TN-C), and capturing thermal images of the distal limb using an HT-19 thermal imaging camera (HTI, La Vergne, TN). In this study, eight healthy horses were exercised for approximately ten minutes per day for five consecutive days. There was a ten-day washout period where the horse received no treatment between each period; there was a total of four periods. The second study only evaluated Rambo®Ionic (Horseware, Dundalk,Ireland) and Ice-Vibe® (Horseware, Dundalk,Ireland) therapeutic boots on seventeen healthy horses in the Virginia Tech equitation lesson program. There were three periods with five days of consecutive data collection and a ten-day washout period in between where the horses received no treatment. Gait analysis was measured using the ALOGO™ MovePro (Alogo Technologies, Switzerland) stride sensor and a blind behavioral analysis was performed to analyze behavioral changes under saddle in response to a rider.

Gait biomechanics have been studied extensively. Many existing studies, though, have been performed in a controlled laboratory setting, and assumed that measures obtained are representative of gait in a naturalistic environment (e.g., outdoors). Several environmental and psychological factors may contribute to differences between these environments, and identifying any such differences is important for generalizing results outside the laboratory. The purpose of this study was to test the implicit assumption that gait inside a research laboratory does not differ from gait outdoors, when a participant is unaware of data collection in the latter. Means and interquartile ranges (IQR) of several spatio-temporal and kinematic gait characteristics were obtained from 19 young adults during several gait conditions both inside a laboratory environment and outdoors. Four comparisons were made between the two environments, including conditions involving: 1) self-selected speeds, 2) matching outdoors self-selected speeds, 3) matching outdoors self-selected speeds while carrying a crate, and 4) matching outdoors hurried speeds. Spatio-temporal variables differed between the two environments in that self-selected walking speed was 1.7% slower inside the lab and cadence was 1.4-2.6% lower for all four comparisons. At heel contact, the foot was 4.4-8.1% more dorsiflexed inside the lab for all comparisons except in matching hurried outdoors walking speed. Minimum toe clearance was 6.5-16.2% lower outdoors for all four comparisons. It is unclear if these differences impair the ability to generalize gait study results to outside the laboratory. Nevertheless, some specific differences exist in gait between environments, and that research should recognize. / Master of Science

Falls due to slipping are a serious occupational concern. Slipping is estimated to cause 40-50% of all fall-related injuries. In 2011, falls resulted in 22% of injuries requiring days away from work. Epidemiological data indicates that older and obese adults experience more falls than young, non-obese individuals. An increasingly heavier and older workforce may be exacerbating the problem of slip-induced falls in the workplace. The purpose of this study was to examine the effects of obesity and age on slip severity and fall outcome following an unexpected slip. Four groups of participants (young obese, young non-obese, older obese, older non-obese) were exposed to an unexpected slip perturbation. Slip severity (slip distance, slip duration, average slip velocity and peak slip velocity) and slip outcome (fall or recovery) were compared between groups. Obese individuals experienced 8.25% faster slips than non-obese individuals in terms of average slip velocity (p=0.022). Obesity did not affect slip distance, slip duration or peak slip velocity. Obese individuals also experienced more falls; 33.3% of obese individuals fell compared to 8.6% of non-obese (p=0.005). Obese individuals were 8.24 times more likely to experience a fall than non-obese individuals, when adjusting for age, gender and gait speed. No age effects were found for slip severity or slip outcome. This study revealed that obese participants experienced faster slips and more falls than their non-obese counterparts. These results, along with epidemiological data reporting higher fall rates among the obese, indicate that obesity may be a significant risk factor for experiencing slip-induced fall. / Master of Science

Slips are a leading cause of injury among older adults. Specific slip recovery measures, including slip distance and peak slip speed, have been shown to increase significantly among fallers as compared to non-fallers. Often, slipping kinematics are measured using optoelectronic motion capture (OMC), requiring a laboratory setting and limiting data collection to experimentally-controlled conditions. Inertial measurement units (IMUs) show promise as a portable and wearable form of motion capture. This study had two objectives. First, we investigated whether foot and ankle IMU-derived slip recovery measures could be considered equivalent to the same OMC-derived measures. Second, we investigated if both participant-placed and researcher-placed IMU-derived slip recovery measures could be considered equivalent to the same OMC-derived measures. 30 older adults (ages 65-80) were exposed to a slip while wearing both IMUs and OMC markers. Slip distance and peak slip speed were measured by both systems and compared. Equivalence testing (α = 0.05) showed that IMUs placed on the foot and the ankle were equivalent to OMC in measuring these slip recovery measures. Furthermore, it was shown that researcher and participant-placed IMUs were equivalent (α = 0.05) to OMC in measuring these slip recovery measures. These results confirm that IMUs can be a viable substitute for OMC and have the potential to expand data capture to a real-world environment. / Master of Science / Falls are a major cause of injury among older adults. Slips are a large contributor to falls, so it is important to better understand how slips occur to develop more efficient fall-prevention programs. To understand slips, previous research often utilized optoelectronic motion capture (OMC) to measure slip recovery measures. However, OMC relies on multiple cameras, limiting slip measurement to a laboratory. As we want to understand slips in the real-world, we must use a different form of motion capture. Inertial measurement units (IMUs) are sensors that can afford real-world biomechanical measurement. In this thesis research, 30 older adults (ages 65-80) were exposed to one over-ground slip. Slip recovery measures are compared between OMC and IMUs placed on the foot and ankle. Furthermore, IMU placement is compared between researchers and participants. Equivalence testing showed that IMUs placed on the foot and the ankle were equivalent to OMC in measuring these slip recovery measures. Furthermore, it was shown that researcher and participant-placed IMUs were equivalent to OMC in measuring these slip recovery measures. These results confirm that IMUs can be a viable substitute for OMC and have the potential to expand data capture to a real-world environment.

Post-mortem human surrogate (PMHS) head specimens were subjected to two different angular speed pulses. Each pulse was approximately a half-sine with either a peak angular speed of either 40 or 20 rad/s and duration of either 30 or 60 milliseconds. High-speed biplane x-ray was used to record the motion of the brain and skull via radio-opaque markers implanted at specified locations in the brain, and lead markers on the skull. Specimens were perfused to physiologic conditions throughout preparation and testing to maintain the integrity of the brain tissue and ensure coupling of the brain and skull. Intracranial pressure was measured anteriorly and posteriorly. The test event was controlled by a cam-follower-flywheel mechanism, which facilitated control of pulse parameters and provided a form of "infinite energy" so that the device and therefore the test input would not be influenced by the characteristics of the object under test. This approach kept the independent and dependent variables separated. The brain targets were also deployed in a prescribed manner with two methodologies that were scalable to different specimens. The repeatable input and target deployment schemes helped reduce experimental variation (between tests and subjects) to produce consistent response data. Displacement of the brain was calculated with respect to a body-fixed basis on the skull. The relative motion of the brain with respect to the skull was shown to be dependent on the location of the target in the brain. The major deformation axis of each target followed the contour of the skull or bony landmark to which it was closest. Intracranial pressure was relatively low because the changes were due to inertial effects in the absence of impact. Tests with lower speeds and longer durations produced less deformation, lower intracranial pressures, and longer pressure durations than the tests that were high-speed, short-duration. The response of the brain to rotation of the head was quantified at two test levels and on two PMHS specimens. / Master of Science / Motor-vehicle collisions (MVCs) are the second leading cause of traumatic brain injury (TBI) in the United States and the leading cause of TBI-related death [1a]. Regulations are in place for vehicle design to reduce the occurrence and severity of head injuries during MVCs. The metric used is based on the resultant linear acceleration at the center of gravity of the occupant’s head. However, TBI are still occurring despite the current regulations. This suggests the importance of using additional injury metrics to predict TBI in MVCs. In automotive impact biomechanics, a combination of real world, experimental, and simulation data is used to determine how the human body responds during MVCs. While computer (finite element) simulations can provide extensive information about the kinematic and kinetic response of the human body, these models require experimental data to validate and evaluate their responses. This study focuses on determining the response of the human cadaver brain to angular speed loading without contact of the head. High-speed biplane x-ray and radiopaque markers were used to quantify the displacement of the brain with respect to the skull throughout rotational events. Two angular speed profiles with different peak angular speeds and durations were used. The methods were determined to reduce experimental variation to obtain data that is useful for finite element model validation. The average peak angular speed for the high-speed tests was 41.8 rad/s and the average peak angular speed for the low-speed tests was 22.0 rad/s. The peak angular speed only varied by 10% between similar tests. The motion of the brain lagged behind that of the skull, producing a relative displacement of the brain with respect to the skull. The magnitude and primary direction of the relative displacement was dependent on the location at which it was measured. The location of the radiopaque target with respect the anatomical coordinate system and bony landmarks of the skull are both important in determining the characteristics of the relative displacement profiles. The high-speed tests produced an average displacement of +/-5 mm, while the low-speed tests had an average displacement of +/-2.5 mm in the X-direction. Intracranial pressure (ICP) was also measured at two points in the cranial cavity, and showed the delayed response of the brain to the rotational loading of the head.

The research presented in this thesis focuses on head impact exposure in youth football. The on-field portion of this research investigated high magnitude head impacts that youth football players experience in games and practices. With previously validated data collection methods, linear and rotational head accelerations from head impacts were collected. Over the course of two seasons, 79 total player-seasons resulted in over 13,000 impacts. A small subset of these, 979 impacts exceeding 40 g, represented the focus of this research as these impacts pose the greatest risk of injury to individuals. Some tackling drills in practice were found to have higher acceleration severities than those observed in games. How practice activities are conducted also contributes towards the overall high magnitude head impact exposure for practice, not just the practice drill itself. Within games, players who are running backs and linebackers played most frequently and experienced higher magnitude impacts more often than their teammates. Data were also collected from all players off the field. Each player completed balance assessments at the beginning and end of the season to allow for comparison, even in absence of a clinically-diagnosed concussion. Current balance assessments were observed to fall short for detecting postural control differences in this youth population. Modifications to these assessments were recommended that might allow for further insights. Research presented in this thesis will inform youth football organizations as they continue to develop strategies to enhance player safety and mitigate head impact exposure. / Master of Science / The research presented in this thesis focuses on head impact exposure in youth football. The on-field portion of this research investigated high magnitude head impacts, which are associated with heightened risk of concussion, that youth football players experience in games and practices. With previously validated data collection methods, the specific causation for high risk head impacts in youth football practices and games was determined for the first time. In some practice drills, players were observed to hit harder and more frequently than they would in games. As youth practices occur more often than games do, limiting the time spent in these types of practice drills is recommended. How practice activities are conducted also contributes towards the overall high magnitude head impact exposure for practice, not just the practice drill itself. Events where players had the opportunity to get up to speed prior to impact were more likely to be high risk than events where players essentially impacted from a standstill. Data were also collected from all players off the field. Each player completed balance assessments at the beginning and end of the season to allow for comparison, even in absence of a clinically-diagnosed concussion. Current balance assessments were observed to fall short for detecting balance differences in this youth population. Modifications to these assessments were recommended that might allow for further insights. Research presented in this thesis will inform youth football organizations as they continue to develop strategies to enhance player safety and mitigate head impact exposure.

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