Browsing by Author "Brolinson, P. Gunnar"
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- Analysis of Force-Limiting Capabilities of Football Neck CollarsMcNeely, David Eugene (Virginia Tech, 2006-05-01)The purpose of this study was to examine football neck collars and determine their effectiveness at preventing transient brachial plexopathy and other neck injuries due to football impacts. Transient brachial plexopathy, commonly called a stinger or burner, is an injury to the brachial plexus. As many as 65% of collegiate football players will receive suffer such an injury. Accessory neck collars are worn to mitigate the risk of stingers, although little research has been performed to test their effectiveness. In addition to the standard shoulder pad and helmet combination, three collars were tested: the McDavid Cowboy Collar, a collar designed by a Virginia Tech physician called the Bullock Collar, and a prototype device called the Kerr Collar. This study utilized a Hybrid-III 50th percentile male outfitted with a standard collegiate football helmet and shoulder pads, and impacted with a linear pneumatic impactor. Forty eight total impacts were performed; impacts were performed at side, front, and axial loading impact locations, with low and high speed impacts, and normal and raised shoulder pad configurations. Each collar was effective at some positions, but no collar was effective at all impact locations. The Cowboy Collar reduced lower neck bending moments in the front position, but raised upper neck bending moments. It also reduced lower neck bending moments in the side position, but only in the raised configuration. The Bullock Collar was effective at reducing lower neck bending moment in the side position. The Kerr Collar was effective at reducing lower neck bending moments in the side impact location, and provided a larger percent reduction in impactor force in the axial loading position, compared to the shoulder pads alone. Further testing is needed at lower impact velocities that more closely represent injurious impacts in the field.
- Analysis of Linear Head Accelerations From Collegiate Football ImpactsManoogian, Sarah Jeanette (Virginia Tech, 2005-04-22)Sports related concussions result in 300,000 brain injuries in the United States each year. The purpose of this study was to utilize an in-helmet system that measures and records linear head accelerations to analyze head impacts from collegiate football. The Head Impact Telemetry (HIT) System is an in-helmet system with six spring mounted accelerometers and an antenna that transmits data via radio frequency to a sideline receiver and laptop computer system. The data reported by the HIT System includes the time of impact, location of impact, and linear acceleration resultant of the head center of gravity. The algorithm and in-helmet application for this system were validated in five series of tests. In particular, the validation emphasized that the HIT System measurements are of the player's head and not helmet accelerations as evidenced by the helmet acceleration being 16.6 (± 3.2) times greater than the peak head accelerations measured by the HIT System and dummy cg accelerometers. Using 130 head impacts in five different test configurations, the mean error in measuring peak linear acceleration was 0.01% (±18%). A total of 11,604 head impacts were recorded from the Virginia Tech football team throughout the 2003 and 2004 football seasons during 22 games and 62 practices from a total of 52 players. The acceleration data distribution was right skewed with a mean impact acceleration magnitude of 20.9 g and maximum value of 172.6 g. The HIC determined for each impact from a 15 millisecond time period was similarly distributed with the mean equal to 17.9, and the maximum equal to 969.6. A total of three impacts with three different players resulted in concussions. These impacts had peak linear accelerations of 55.7 g, 136.7 g, and 117.6 g with HIC values of 120.6, 518.4, and 355.6 respectively. Each of these hits was among the highest recorded for each respective player. Although the incidence of injury data is limited, this study presents an extremely large data set from human head impacts that provides valuable insight into the lower bounds of mild traumatic brain injuries.
- Assessing Symmetry in Landing Mechanics During Single-Leg and Bilateral Tasks in Healthy Recreational AthletesMcConnell, Evan Paul (Virginia Tech, 2017-07-14)INTRODUCTION: ACL-reconstructed (ACL-R) patients exhibit side-to-side asymmetries in movement and loading patterns after surgery, some of which are predictive of a secondary ACL injury. These asymmetries have not been fully assessed in healthy athletes. PURPOSE: To quantify side-to-side symmetry in secondary injury predictors in healthy athletes and compare these metrics to those measured in previous cohorts of ACL-R patients, as well as to assess differences in these metrics between two landing tasks and between sexes. METHODS: 60 healthy recreational athletes performed seven trials of a stop-jump task and seven trials of a single-leg hop for distance on each limb. The kinematics and kinetics of the first landing of the stop-jump and the landing of the single-leg hop were analyzed with a 10-camera motion analysis system (240Hz) and 2 embedded force plates (1920Hz). Limb symmetry indices (LSIs) were calculated for each variable and compared between subject groups, tasks, and sexes with Wilcoxon Signed Rank tests (p<0.05). RESULTS: Control subjects exhibited asymmetry in hop distance (p=0.006). ACL-R subjects displayed greater asymmetry in knee flexion variables, peak forces, and peak knee extension moments during the bilateral landing (p<0.001) and in hop distance (p<0.001). Control subjects showed greater asymmetry in knee flexion variables during the single-leg hop (p<0.001). Males and females showed similar symmetry in both tasks. CONCLUSIONS: Symmetry cannot be assumed in control subjects in all metrics. Asymmetries are more prevalent in ACL-R athletes than in healthy controls. Future work will continue to examine the usefulness of each metric in assessing ACL-R rehabilitation.
- Biomechanical Investigation of Head Kinematics and Skull StiffnessSeimetz, Christina N. (Virginia Tech, 2011-05-31)This thesis presents two studies related to head injury. The study presented in Chapter 1 reviewed findings of cranial movement in animal and human specimens and evaluate the validity of cranial movement due to manual manipulation in humans through engineering analysis. The study had two parts. In Part I, the literature was reviewed to determine the cranial motion in animals and humans. Engineering analysis was done in Part II to determine the amount of force necessary to cause cranial motion in the studies from Part I using skull stiffness values from published studies. Chapter 2 explored data collection methodologies used in frontal sled tests. Several data collection methodologies exist for collecting kinematic data, such as Vicon motion analysis, video analysis, and sensors. Head trajectories from motion data and accelerometer data were plotted up to maximum forward excursion of the head for eight frontal sled tests, four conducted at Virginia Tech and four at the University of Virginia. In addition, the percent difference between maximum forward excursion values from sensor and motion data were calculated. Finally, Chapter 3 discusses the literary contributions of each study and to which journals they will be submitted.
- Biomechanics of Head Impacts in SoccerPress, Jaclyn Nicole (Virginia Tech, 2016-09-22)An estimated 3.8 million sports-related concussions occur every year. Little research has been collected on soccer players, despite women's soccer having the third highest rate of concussion among all popular collegiate sports. The objective of this work was to evaluate multiple interventions that have been introduced to address the high rate of concussions in this population. Wearable head impact sensors were evaluated on their ability to accurately count and measure head impacts during a collegiate women's soccer season. Head impact exposure was quantified using video analysis of this season as well. Sensors were unable to accurately count impacts and reported nonsensical head acceleration measurements, indicating that data reported from head impact sensors should be interpreted with caution. The ability of soccer headgear to reduce linear and rotational head accelerations during common soccer impacts was examined in the laboratory. Ball-to-head and head-to-head impacts were performed at a range of speeds and impact orientations. Headgear resulted in small reductions during ball-to-head tests, which are not likely to be clinically relevant. In head-to-head tests, use of headgear on the struck head provided an overall 35% reduction in linear head acceleration, and a 53% reduction when another headgear was added to the striking head. The ten headgear tested varied greatly in performance. These data suggest that the use of protective headgear could reduce concussion incidence significantly in this population. Research presented in this thesis will inform soccer organizations on best practices for player safety with regard to head impacts.
- The Biomechanics of Thoracic Skeletal ResponseKemper, Andrew R. (Virginia Tech, 2010-03-30)The National Highway Traffic Safety Administration (NHTSA) reported that in 2008 there were a total of 37,261 automotive related fatalities, 26,689 of which were vehicle occupants. It has been reported that in automotive collisions chest injuries rank second only to head injuries in overall number of fatalities and serious injuries. In frontal collisions, chest injuries constitute 37.6% of all AIS 3+ injuries, 46.3% of all AIS 4+ injuries, and 43.3% of all AIS 5+ injuries. In side impact collisions, it has been reported that thoracic injuries are the most common type of serious injury (AIS≥3) to vehicle occupants in both near side and far side crashes which do not involve a rollover. In addition, rib fractures are the most frequent type of thoracic injury observed in both frontal and side impact automotive collisions. Anthropomorphic test devices (ATDs), i.e. crash test dummies, and finite element models (FEMs) have proved to be integral tools in the assessment and mitigation of thoracic injury risk. However, the validation of both of these tools is contingent on the availability of relevant biomechanical data. In order to develop and validate FEMs and ATDs with improved thoracic injury risk assessment capabilities, it is necessary to generate biomechanical data currently not presented in the literature. Therefore, the purpose of this dissertation is to present novel material, structural, and global thoracic skeletal response data as well as quantify thoracic injury timing in both frontal belt loading and side impact tests using cadaveric specimens.
- Chemosensory Evaluation of Training and Oxidative Stress in Long Distance RunnersWhysong, Christan Yvonne (Virginia Tech, 2014-05-28)Athletes complete a balance of training loads and rest periods, risking overtraining when this balance favors excessive training. Diagnostic biomarkers have been suggested but a clear diagnostic method is not available. This preliminary study's objective was to use data standardization to improve an electronic nose's (enose) discrimination model for athletes' breathprints after cumulative and acute training loads. Collegiate long distance runners were observed throughout competitive training seasons. Prolonged training effects were observed through Profile of Mood States (POMS) surveys and blood and breath samples collected at the beginning (Pre-Study) and end of the training season (Post-Study). Immediate training effects were observed for one low (LI) and one high (HI) intensity acute training load. Subjects provided blood and breath samples before the LI (BSR) and HI (BLR), completed the training load, and provided blood and breath samples after each training load (ASR; ALR). Blood was analyzed for antioxidant enzymes (catalase, glutathione peroxidase, and glutathione reductase). Breath samples were analyzed with a Cyranose® 320 (C320) enose. Age, gender, and training loads affected oxidative states, with the HI having more effect than the LI. Mood profiles indicated healthy and successful athletes. Neither POMS nor blood parameters suggested overtrained athletes. The C320 successfully discriminated between breathprints of athletes correlating to the training loads. Direct data standardization through carbon dioxide as a baseline sensor purge correctly classified 100 percent of the data through linear discriminant analysis (LDA). Indirect data standardization by subtracting Pre-Study data from the subsequent data classes (e.g. BSR) correctly classified 96 percent of the data. An LDA on the combined blood parameters correctly classified 61.9 percent of the data. The blood analyses required invasive sample collections and involved procedures that took a long time (hours). In comparison, the best C320 model correctly classified 96 percent of the data and required less invasive sample collections, simple analysis, and short result times (minutes). Evidence suggested the C320 will provide a simple and noninvasive method for clinically diagnosing the onset of overtraining. The unit is small, handheld, rapid, and noninvasive so it could also be used on- site to provide immediate feedback for training optimization.
- Chemosensory Evaluation of Training and Oxidative Stress in Long Distance RunnersWhysong, Christan (Virginia Tech, 2009-10-28)Athletic performance is improved by increasing training loads but it is difficult to determine an athlete's response to a training load and the amount of stress incurred. This makes athletes susceptible to overtraining, leading to decreased performance levels, due to physical exhaustion and oxidative stress. Past studies have observed a myriad of biomarkers without conclusively identifying a clinically specific marker for overtraining due to oxidative stress. These methods require invasive testing and lengthy result times, making real-time adjustments of training programs to prevent overtraining difficult. The use of an electronic nose (enose) as a non-invasive evaluation tool will provide immediate feedback on training stress, allowing for real-time training adjustments for performance optimization. Two long distance runners (one male and one female) completed a pilot study. Both performed a short run and the female performed a long run. Blood samples were collected from each athlete before and after each run and analyzed for catalase and GPx activity. Breath samples were also collected before and after each run and analyzed by an enose. Multivariate analyses of combined blood data yielded better results than individual analyses. Although data was limited for this pilot study, canonical discriminant analyses (CDA) showed separation between before and after run and between short and long run breath samples. Cross validations also found up to a 77.8 percent prediction accuracy for the enose. Results indicate an enose is feasible for detecting changes in the breath occurring after physically demanding exercise perhaps due to oxidative stress incurred during the exercise.
- Developing a Living Composite Ligament by Combining Prolotherapy and Nanoparticles as Treatment for Damaged Connective TissueEmpson, Yvonne Marie (Virginia Tech, 2014-05-06)Significant cost and debilitation results from connective tissue injury and disease every year. Prolotherapy is an effective medical treatment used to increase joint stability. However, most associated studies are retrospective or case studies, rather than comprehensive laboratory investigation originating with the cellular response to exposure to the proliferant solutions. As a parallel consideration, nanoparticles are being investigated for use in drug delivery and heat shock treatment of cancerous tissue due to their unique structural and thermal properties. The phenomenal strength and stiffness of carbon nanoparticles have been used for commercial purposes in composite materials, but investigation of biomedical applications is still fairly nascent. In an attempt to develop a non-surgical approach to supporting and healing damaged ligaments and tendons resulting from injury or disease by combining prolotherapy and the use of nanoparticles, the author presents studies investigating the cellular response to proliferative therapy solution as well as tendon and ligament tissue's mechanical and cellular response to exposure to nanoparticles. In the prolotherapy solution cell studies, the results suggested that there is an optimal dosage of the proliferant for in vitro studies, different responses between cell types, and a dosage-dependent response in cell viability and collagen production to the solution P2G in preosteoblasts. In the nanoparticle studies, cell populations tolerated nanoparticles at the levels tested, tendon mechanical properties were increased (stiffness significantly so), and bright field and transmission electron microscopic histological images were taken of connective tissue and carbon nanohorn interactions.
- The Development and Validation of a Biofidelic Synthetic Eye for the Facial and Ocular CountermeasUre Safety (FOCUS) HeadformKennedy, Eric A. (Virginia Tech, 2007-08-03)There are over 1.9 million eye injuries per year in the United States with over 30,000 patients left blind in at least one eye as a result of trauma. Some of the most severe eye injuries can occur in automobile accidents and from sports related impacts. Eye injuries in the military environment are even more prevalent and are generally more severe than eye injuries to civilians. The rate of eye injuries has dramatically increased in warfare in recent years, rising from 2% of all casualties during World War I and World War II to over 13% of all combat injuries in Operation Desert Storm. While many of the conflict-related eye injuries are caused by shrapnel and other debris, nearly 25% of the injuries are also caused by blunt trauma from motor vehicle and helicopter crashes, falling, and direct hits from blunt objects. In order to develop safety countermeasures effective at preventing these eye injuries, as well as evaluate the eye injury potential of different impacts, it is desirable to have the capability for distinguishing between injurious and non-injurious eye impacts. Current anthropometric test device (ATD) headforms lack instrumentation and facial features to allow detailed assessment of eye or discrete facial injuries. Therefore, the purpose of this dissertation is to present the development and validation of the Facial and Ocular CountermeasUre Safety (FOCUS) headform's synthetic eye and orbit and corresponding eye injury risk criteria.
- Effects of Fatigue & Gender on Peroneal Reflexes After Ankle InversionWilson, Erin Lawall (Virginia Tech, 2005-05-02)An estimated 23,000 ankle injuries occur every day in the U.S. Ankle sprains account for 85% of all ankle injuries and inversion ankle sprains account for 85% of all ankle sprains. There is growing evidence that suggests gender and fatigue may increase the risk for inversion ankle sprains. Investigating the effects of fatigue and gender on peroneal reflex response after ankle inversion may help explain the differences in sprain rates with fatigue and gender. Therefore, the purpose of this study was to investigate the effects of fatigue and gender on peroneus brevis and peroneus longus reflexes after ankle inversion. A "trap-door" platform was used to elicit peroneal reflexes from sixteen males and fifteen females by suddenly inverting the ankle to 20°. Five unfatigued peroneal reflex measurements were performed before and after a fatigue protocol that attempted to fatigue the ankle evertors over 12 minutes to 75% of the unfatigued MVC torque. Results showed that reflex delay was not affected by fatigue, gender, or their interaction. PL reflex amplitude was not affected by fatigue or gender but was affected by their interaction. Results showed that PL reflex amplitude decreased by 11.3% in males and increased 22.1% in females with fatigue. A secondary analysis attempted to rule out extraneous factors that could have contributed to the differences in reflex response, but no experimental explanations were found. The differences in PL reflex amplitude were attributed to biomechanical, physiological, and anatomical differences between males and females.
- Evaluating the Head Injury Risk Associated with Baseball and SoftballMorris, Tyler Pierce (Virginia Tech, 2018-06-07)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.
- Evaluation and Application of Brain Injury Criteria to Improve Protective Headgear DesignRowson, Bethany M. (Virginia Tech, 2016-09-01)As many as 3.8 million sports-related traumatic brain injuries (TBIs) occur each year, nearly all of which are mild or concussive. These injuries are especially concerning given recent evidence that repeated concussions can lead to long-term neurodegenerative processes. One way of reducing the number of injuries is through improvements in protective equipment design. Safety standards and relative performance ratings have led to advancements in helmet design that have reduced severe injuries and fatalities in sports as well as concussive injuries. These standards and evaluation methods frequently use laboratory methods and brain injury criteria that have been developed through decades of research dedicated to determining the human tolerance to brain injury. It is necessary to determine which methods are the most appropriate for evaluating the performance of helmets and other protective equipment. Therefore, the aims of this research were to evaluate the use of different brain injury criteria and apply them to laboratory evaluation of helmets. These aims were achieved through evaluating the predictive capability of different brain injury criteria and comparing laboratory impact systems commonly used to evaluate helmet performance. Laboratory methods were developed to evaluate the relative performance of hockey helmets given the high rate of concussions associated with the sport. The implementation of these methods provided previously unavailable data on the relative risk of concussion associated with different hockey helmet models.
- Evaluation of Football Safety Techniques Utilizing Biomechanical MeasurementsDaniel, Ray W. II (Virginia Tech, 2014-08-19)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.
- Evaluation of Gait and Slip Characteristics for Adults with Mental RetardationHaynes, Courtney Ann (Virginia Tech, 2008-11-19)Adults with mental retardation (MR) experience a greater number of falls than their non-disabled peers. To date, efforts to understand the causes for these falls have primarily involved qualitative studies that use largely subjective measures to quantify stability. Performing a more objective biomechanical gait analysis may better explain the reasons for these fall accidents and provide repeatable measures that can be used for comparison to determine the effectiveness of interventions intended to reduce slip-related falls. A gait analysis was conducted to quantify normal walking and slip response characteristics for adults with MR as well as a group of non-disabled age- and gender-matched peers. Kinetic and kinematic data were collected and a number of variables relating to gait pattern, slip propensity, and slip severity were calculated to compare the differences between groups. Results showed that adults with MR exhibit slower walking speeds, shorter step lengths, and greater knee flexion at heel contact suggesting that their gait patterns share more similarities with the elderly than with healthy adults of an equivalent age. Unexpectedly, the MR group demonstrated a lower required coefficient of friction (RCOF) and slower heel contact velocity which, alone, would suggest a reduced slip propensity as compared with the healthy group. A greater peak sliding heel velocity and greater slip distance measures, however, indicate greater slip severity for the MR group. The findings of this study suggest that falls in this population may be attributed to delayed response to slip perturbation as measured by slip distances.
- Evaluation of the Biomechanical Performance of Youth Football HelmetsSproule, David William (Virginia Tech, 2017-05-23)Youth and varsity football helmets are currently designed similarly and tested to the same impact standards from the National Operating Committee on Standards for Athletic Equipment (NOCSAE). Youth players have differences in anthropometry, physiology, impact exposure, and potentially injury tolerance that should be considered in future youth-specific helmets and standards. This thesis begins by investigating the current standards and relating them to on-field data. The standard drop tests represented the most severe on-field impacts, and the performance of the youth and varsity helmet did not differ. There likely is not a need for a youth-specific standard as the current standard has essentially eliminated the catastrophic head injuries it tests for. As more is known about concussion, standards specific to the youth population can be developed. The second portion of this thesis compares the impact performance between 8 matched youth and varsity helmet models, using linear acceleration, rotational acceleration, and concussion correlate. It was found that helmet performance did not differ between the youth and varsity helmets, likely attributed to testing to the same standard. The final portion of this feature is aimed at advancing STAR for youth and varsity football helmets by including linear and rotational head kinematics. For varsity helmets, an adult surrogate is used for impact tests which are weighted based on on-field data collected from collegiate football players. For youth helmets, a youth surrogate is used and tests are weighted based on data collected from youth players.
- Identifying High Risk Individuals in Youth Football and Evaluating Tackling TechniqueGellner, Ryan Aaron (Virginia Tech, 2018-05-11)Nearly 3.5 million kids play youth football every year in the United States, many in independent organizations with few or no rules for limiting head impact exposure in practices or competition. Studies have found potential long-term effects of repetitive head impact exposure from a young age, even in the absence of concussion. The best methods for reducing head impact exposure include a multi-pronged approach: limiting contact through rules changes, teaching proper technique for contact when it does occur, and designing equipment with better protective capabilities. Four youth football teams were studied for one season each using helmet mounted accelerometer arrays. Head acceleration data indicated that youth teams often have a small subset of players who account for a disproportionately large number of high-risk head impacts. As few as six players (6%) accounted for over 50% of all high-risk impacts seen in practice sessions. Technique used during tackling and tackle-absorption had considerable effect on head acceleration. Both the tackler and ball carrier were found to be at greater risk for high magnitude head impacts when exhibiting poor form as defined by specific tackling recommendation criteria. These data suggest that individualized interventions encouraging proper form, especially for a subset of impact-prone players, may be beneficial in reducing high magnitude head impact exposure for an entire youth football team. This is especially critical because a majority of high-risk impacts are experienced in practice at the youth level. Results from this work could be applied by coaching staffs in youth football leagues to increase the safety of their athletes.
- Laboratory and Field Studies in Sports-Related Brain InjuryCobb, Bryan Richard (Virginia Tech, 2015-04-21)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.
- Longitudinal Locomotor and Postural Control Following Mild Traumatic Brain InjuryFino, Peter C. (Virginia Tech, 2016-02-05)Millions of people sustain a mild traumatic brain injury (concussion) each year. While most clinical signs and symptoms resolve within 7-10 days for the majority of typical concussions, some gait and balance tasks have shown abnormalities lasting beyond the resolution of clinical symptoms. These abnormalities can persist after athletes have been medically cleared for competition, yet the implications of such changes are unclear. Most prior research has examined straight gait and standard measures of balance, yet there is a lack of knowledge regarding potential persistent effects on non-straight maneuvers or on indicators of motor control variability or complexity. To expand the knowledge of post-concussion locomotor and postural changes, this investigation examined the recovery of recently concussed athletes longitudinally, over the course of one year, in three domains: 1) path selection and body kinematics during turning gait, 2) non-linear local dynamic stability during straight gait, and 3) postural control complexity during quiet standing. Compared to matched health controls, concussed athletes exhibited significant and persistent differences in turning kinematics, local dynamic stability, and postural complexity over the initial six weeks following injury. These motor differences may increase the risk of injury to concussed athletes who are cleared to return to play. Given the persistent nature of these effects, future clinical tests may benefit from incorporating gait assessments before returning athletes to competition. Future research should prospectively and longitudinally monitor locomotor and postural control in conjunction with structural and functional changes within the brain to better understand the pathophysiology of concussions and potential rehabilitation strategies.
- On-Field Measurement of Head Impacts in Youth Football: Characterizing High Magnitude Impacts and Assessing Balance OutcomesCampolettano, Eamon Thomas (Virginia Tech, 2017-05-15)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.