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. / MS / Baseball and softball are two commonly played sports, however, they combine to yield some of the highest head injury rates among sports. Safety measures like protective headgear and softer balls have been implemented into the games, but there is currently no metric for comparing different models and brands on their effectiveness at reducing head injury. The research in this thesis provides an evaluation system that compares the effectiveness of protective headgear between different models and brands and their ability to reduce head injury. This research is presented to the public as a purchasing tool and can be used to further improve the safety in baseball and softball.

The pattern and complexity of cerebellar folding varies across vertebrates. However, little is known about how the tissue-level mechanics are adjusted to create species-specific folding patterns. Here, we utilize a variety of species with differences in cerebellar folding amount to investigate two tissue-level mechanics known to affect folding—differential expansion and outer layer thickness. We found that the level of differential expansion between the outer and inner layers of the cerebellum broadly correlates with folding amount and that the thickness of the outer layer is important as thicker outer layers require more differential expansion to fold. Additionally, we find that both the proliferation rate and division angle of cells in the outer layer are adjusting these two mechanics. This work will shed light on the conservation of the tissue mechanics that regulate brain folding and how these mechanics may be modulated to set the diverse folded morphologies observed across species.

Maize is the most grown crop in the world. Each year, 5% of maize is lost due to a phenomenon known as stalk lodging (breakage of the stalk below the ear). One of the most promising solutions to stalk lodging is to design stalks with superior geometry to increase stalk strength. Researchers have developed a 3D parameterized maize stalk model, but these models take a long time to structurally analyze and are missing important material properties. This thesis addressed these problems by developing an automated package for analyzing the 3D parameterized maize stalk model, and by measuring the longitudinal shear modulus of both pith and rind stalk tissues. This thesis also identified the most influential geometric patterns in the 3D parameterized maize stalk model, which can be used to breed stronger maize. The results of this thesis are an increased understanding of the factors that influence stalk lodging, and geometric details for how stronger maize can be designed.

Gap crossing is a regular locomotor activity for arboreal animals. The distance between branches likely plays a role in determining whether an animal is capable of crossing a given gap, and what locomotor behavior it uses to do so. Yet, despite the importance of gap distance as a physical parameter influencing gap crossing behavior, the precise relationships between gap distance and movement kinematics have been explored in only a very small number of species. One particularly interesting group of arboreal inhabitants are the flying snakes (Chrysopelea). This species is able to use a dynamic "J-loop" movement to launch its glides, but it is not known whether it is also capable of using such jumps to cross smaller gaps between tree branches. This dissertation addresses this knowledge gap, and investigates the influence of gap distance on crossing behavior and kinematics in three closely-related species of snake: Chrysopelea paradisi, a species of flying snake, and two species from the sister genus, Dendrelaphis, neither of which can glide. Chapter 2 is a literature review of the biomechanics of gap crossing, specifically focusing on the role played by gap distance, and establishes the context for the rest of the work. Chapter 3 presents a detailed study of how increasing gap size influences the behavior and kinematics of gap crossing in C. paradisi, showing that this species uses increasingly dynamic movements to cross gaps of increasing size. Chapter 4 explores the same relationships between gap size and kinematics in D. punctulatus and D. calligastra, revealing remarkable similarities between the three species, suggesting the possibility that dynamic gap crossing may have evolved prior to gliding in this clade. Finally, chapter 5 addresses the role played by gap distance in limiting the non-dynamic, cantilever movements used by these species to cross small gaps, comparing observed stopping distances to those predicted by various torque-related limitations. / Doctor of Philosophy / To successfully cross a gap, an animal must be able to reach or jump from one side to the other. Animals who live in trees must do this quite frequently, as they live among the branches and there are often not connected paths from one place to another. But we don't know very much about how the distance between two structures (the "gap distance") affects the ways an animal moves between them. In this dissertation, I explore how gap distance changes the way a few special species of snakes cross a gap. The species I am studying are special because one species, the paradise tree snake, can glide. Because this 'flying' snake launches its glides by doing a big jump, it is possible that the snake can also jump between tree branches, but this question has never been examined before. We also don't know how the ability to do big jumps evolved, so I studied how distance affects the way two very closely related species of snake, the common tree snake and the northern tree snake, cross gaps. By looking at all of these species, we can understand more about what kinds of behavior are specific to the flying snakes, and which are present in related species. Finally, I also explore how gap distance limits the way the snakes cross gaps when they are not jumping. When the snakes do not jump, they have to hold themselves out straight off the end of a branch. This requires a lot of muscular effort, which means they can't go as far. The fact that the non-jumping behavior is distance-limited might help explain why the snakes need to jump. Altogether, the projects in this study help us understand how gap distance influences what behavior an animal chooses to cross the gap, and increases our knowledge of how flying snakes and their relatives cross gaps in particular.

Virtual reality (VR) has been successfully applied to a broad range of training domains; however, to date there is little research investigating its benefits for sport training. In this work we investigated the feasibility and usefulness of using VR for two sport subdomains: sport psychology and sport biomechanics. In terms of sport psychology training, high-fidelity VR systems could be used to display realistic 3D environments to induce anxiety, allowing resilience-training systems to prepare athletes for real-world, high-pressure situations. For sport biomechanical training, we could take advantage of the 3D tracking available in VR systems to capture and display full-body movements in real-time, and could design flexible 3D environments to foster a valuable and engaging training experience. To address using VR for sport psychology training, in this work we present a case study and a controlled experiment. Our work addresses whether a VR system can induce anxiety in participants, and if so, how this anxiety impacts performance, and what the implications are for VR system design. sing VR for sport biomechanical training, in this work we present a case study describing the development of a VR-based jump training application. Our work addresses whether an effective VR biomechanical training system can be achieved using standard computer equipment and commodity tracking devices, and how we should design the user experience of a VR sport training system to effectively deliver biomechanical principles. / Master of Science

Exoskeletons are wearable assistive devices made to be worn by users to enhance the function of the joint, reduce metabolic costs, and reduce required biological work. This thesis looks at several different types of knee exoskeletons and how they affect the user’s biomechanics and reduce the tibiofemoral force experienced by the user. Tibiofemoral forces are one of the joint contact forces experienced at the knee and are dependent on the level of activity from the surrounding muscles (DeMers et al., 2014). The knee is one of the largest joints in the human body, but is also prone to injury and degradation, with a global incidence of 203 per 10,000 people developing knee osteoarthritis (Cui et al., 2020). Everyone’s step-by-step biomechanics are going very slightly but summed together the muscle activity will be very similar (Ivanenko et al., 2004). This makes it easy to design an exoskeleton for the common man and make slight alterations as needed. Through this literature review, it will be shown that powered exoskeletons can be effective at reducing the tibiofemoral forces during a variety of conditions, and are best suited by targeting the knee extensor muscles.

In a 1994 survey, on incidence rates of musculoskeletal injuries among private industries within the U.S, nurses ranked first nationally. Patient handling tasks are considered to be a precipitating factor in the development of many musculoskeletal injuries. For many decades personnel training has been an intervention widely used for the nursing back problem. Inconsistency regarding the effectiveness of many personnel training programs, lack of controlled research among existing studies, and a primary focus only on long term reduction of injury rates makes the interpretation of the success of personnel training programs a difficult one. This study is based on the assumption that, if a training program is to be effective as a means of reducing musculoskeletal injuries, it must first modify worker behaviors and biomechanical stresses to a measurable degree. This research investigated the effects of training (Video and Lecture/Practice) on modifying working behaviors and biomechanical stress. Two tasks were examined (wheelchair to bed and lift up in bed) with two types of assistance (one-person or two-person) and two levels of patient's dependence (semi-dependent or dependent). Changes in behaviors were examined immediately following training (1-2 days delay) and after a short period of time (4-6 weeks) and evaluated using the criteria of subjective ratings of exertion, and postural and biomechanical measures. Results indicated that training led to several significant changes in the knee, hip, elbow and torso angles, whole body, shoulders and low back RPE, shear forces and shoulder moments. No differences were observed in these measures after a short period of time, suggesting retention of the information presented during the training programs. Results as a whole suggest that training can positively affect the working postures and biomechanical stress during common patient handling tasks. All the postural changes and biomechanical measures were advantageous in terms of reducing musculoskeletal stress. It was also found that after a short period of time (4-6 weeks) still retained the information presented during the training programs. Training using a combination of lecture and practice in some cases achieved better results than Video-based training. / Master of Science

In 2021, over three and a half million women entered the postpartum period in the United States [1]. Despite their prevalence, postpartum health is a largely overlooked area. After delivery, 25% of women within this population experience lumbopelvic or pelvic pain during the typical postpartum period [3], up to 8 weeks post-delivery, and research has found these women may continue to experience pain years after delivery [4]. Persistent pelvic region pain in postpartum women may result in lower limb load asymmetry. Additionally, external loading from carrying a child may alter the degree of asymmetric loading that exists in the lower limbs. Therefore, the first purpose of this study was to investigate the effect of daily tasks on lower extremity load symmetry using metrics that have successfully identified load asymmetry in other populations. Load symmetry was found to differ between task, with the largest asymmetry occurring between limbs during the sit-to-stand task for the peak impact force (PIF = 9.08% symmetry) and during the stair descent task for the average loading rate (ALR = 15.43% symmetry). The increase in asymmetry during these tasks may be attributed to increased muscle activation and force production. The second purpose of this study was to investigate the effect of an external child load on lower extremity load asymmetry during a 14-meter level walking task. A significant increase was found between the no load and both child load conditions for PIF and ALR (p <0.001 for both metrics). No statistically significant differences in symmetry were found between carrying the child centrally in a carrier and carrying on one side of the body without a carrier. The lack of difference in asymmetry during child carrying conditions may indicate mothers naturally compensate for the external child load as both ALR and PIF values increased during these conditions, but asymmetry was not impacted. Our results indicate the need to continue to examine different carrying conditions in postpartum women to better understand risk factors for pain or injury and provide evidence-based recommendations for postpartum activity progression. / Master of Science / In 2021, over three and a half million women entered the postpartum period in the United States [1]. Despite their prevalence, postpartum health is a largely overlooked area and 25% of women experience low back or pelvic pain past the typical postpartum period of 8 weeks post delivery [3]. Research has found women may continue to experience this pain years after delivery and result from the lower limbs being loaded unequally. The extra weight from carrying a child may also impact the amount of unequal loading placed onto the lower limbs. The first purpose of this study was to investigate the effect of daily tasks on load symmetry in the lower limbs using measures that have successfully identified unequal load distribution in non-pregnant individuals. Load symmetry was found to differ between task, with the largest asymmetry occurring between limbs during the sit-to-stand task for the force applied to lower limbs during initial contact of the feet and during the stair descent task for the rate that force was applied to lower limbs. The second purpose of this study was to investigate the effect of an external child load on lower extremity load asymmetry during a 14-meter level walking task. A significant increase was found between the no load and both baby load conditions for force applied during initial contact of the feet and rate this force was applied. No difference was found between child carrying external loading condition when evaluating asymmetry. Our results indicate the need to continue to investigate the unique loading patterns of postpartum women to better understand the specific risk factors for pain or injury development within this population.

Abstract Background: Osteoarthritis (OA) is a prevalent joint disease causing significant disability, particularly in the knee often treated end-stage with joint replacement surgery. While partial knee arthroplasty (PKA) is noted for quicker recovery and better functionality compared to total knee arthroplasty (TKA), its underutilization highlights a gap in surgical decision-making, driven by a lack of objective data on pre-operative functional differences. Methods: This prospective observational study, conducted from November 2023 to April 2024 at St. Joseph’s Healthcare Hamilton, included 34 end-stage OA patients scheduled for knee arthroplasty. Participants underwent pre-operative functional assessments using markerless motion capture technology to analyze gait and mobility during walking and sit-to-stand tests. Results: The study found no significant differences in basic gait and sit-to-stand metrics between the PKA and TKA groups at a preferred pace. However, at a faster pace, PKA patients demonstrated greater adaptability, showing significant increases in peak stance knee flexion, knee flexion excursions, and stride length, compared to TKA patients whose gait patterns remained consistent across speeds. Conclusion: PKA patients exhibit greater functional adaptability in their pre-operative state, suggesting potential underestimation of their capabilities in current surgical evaluations. Incorporating varied-pace walking tests in pre-operative assessments may provide deeper insights into functional capabilities, influencing more tailored surgical decisions and potentially increasing the application of PKA in suitable candidates. / Thesis / Master of Applied Science (MASc)

<p>Between October 2001 and May 2012 approximately 70% of U.S. military personnel killed in action and 75% wounded in action were the direct result of exposure to an explosion. As of 2008, it was estimated that close to 20% of all Operation Iraqi Freedom and Operation Enduring Freedom (OIF/OEF) veterans had sustained some form of traumatic brain injury (TBI). Further, blast exposure is also a civilian problem due to the increased usage of explosives in terrorist attacks. Blast injury research has historically focused on the pulmonary system and the other air-containing organs which have been shown through extensive experimentation to be susceptible to blast overpressure injury. A shift in injury pattern during recent conflicts is characterized by decreased incidence of pulmonary injuries with an increase in TBI thought to be associated with blast exposure. This increase in observation of blast TBI has resulted in a large research effort to understand mechanisms and thresholds. However, due to the relatively sudden shift, much of this research is being conducted without a proper understanding and consideration of blast mechanics and interspecies scaling effects.</p><p>This dissertation used experimental and computational finite element (FE) analysis to investigate some large questions surrounding blast TBI research. An experimental investigation was conducted to determine the effects of modern thoracic body armor usage on blast pressure exposure seen by the body. To improve FE modeling capabilities, brain tissue mechanics in common blast TBI animal model species were investigated experimentally and computationally to determine viscoelastic constitutive behavior and measure interspecies variation. Meta-analysis of blast pulmonary literature was conducted to update interspecies scaling and injury risk models. To derive interspecies scaling and injury risk models for blast neurotrauma endpoints a meta-analysis of existing experimental data was used.</p><p>This dissertation makes major contributions to the field of injury biomechanics and blast injury research. Research presented in this dissertation showed that modern thoracic body armor has the ability to lower the risk of pulmonary injury from blast exposure by attenuating and altering blast overpressure. The study shows that the use of soft body armor results in the pulmonary injury threshold being similar to that for neurotrauma. The use of hard body armor results in the threshold for pulmonary injury occurring at higher levels than that of neurotrauma. This finding is important, as it helps to explain the recent shift in injury types observed and highlights the importance of continued widespread usage of body armor not only for ballistic protection but for protection from blast as well.</p><p>This dissertation also shows the importance of interspecies scaling for investigation of blast neurotrauma. This work looks at existing in vivo animal model data to derive appropriate scaling across a wide range of brain size. Appropriate scaling for apnea occurrence and fatality for blast isolated to the head was found to be approximately equal to a characteristic length scaling of brain size, assuming similar brain geometry. By combining the interspecies scaling developed and existing tests data, injury risk models were derived for short duration blast exposures.</p><p>The contributions and conclusions of this dissertation serve to inform the injury biomechanics field and to improve future research efforts. The consideration by researchers of the recommendations presented in this dissertation for in vivo animal model testing will serve to maximize the value gained from experimentation and improve our understanding of blast injury mechanisms and thresholds. The injury risk models presented in this work help to improve our ability to prevent, diagnose, and treat blast neurotrauma.</p> / Dissertation