The knee is the most common site of osteoarthritis (OA) and is one of the leading causes of disability in older adults affecting over 53 million people in the United States and more than 302 million people worldwide. These numbers are only expected to grow because of the rise of diseases such as obesity, demographic shifts to an older population, and a more sedentary lifestyle. The rise of obesity and a more sedentary lifestyle comes with increases in joint loading which along with the aging population creates worse outcomes in proprioception. All of which can contribute to worsening OA. Despite the great costs to quality of life and society, there is no cure for OA. Only treatments exist to treat the symptoms of OA; and since knee pain is one of the most common symptoms of OA, it is a powerful driver for treatment because of the disruptive nature it can have on quality of life. Therefore, many treatments focus on pain relief and exercise to reduce the pain and worsening of OA. Radio frequency nerve ablation (RFA) is a procedure that is increasingly being performed for those who want an alternative before resorting to or are not a good match for total knee arthroplasty (TKA). Because RFA is minimally invasive, it can be performed on an outpatient basis and has been shown to be effective in reducing pain for at least 24 months for most patients. Despite the benefits in pain reduction, little is known about the biomechanical effects of RFA and its consequences on proprioception. However, based on prior studies into the pain relieving effects of interventions such as celecoxib or HA injections, we can hypothesize that with a decrease in pain, knee loading increases. Therefore, the pain relieving effects of RFA may increase the incidence of OA. Furthermore, because the RFA procedure involves ablating nerves that carry sensory information, changes to proprioception are expected. However, currently there is no information regarding its effect on proprioception. Again, using prior research that studies the consequences of reduced proprioception on those with OA, we can hypothesize that with RFA, proprioception would be further reduced compared to the reductions experienced by people with OA already, and it may also lead to worsening OA outcomes. Despite the possible issue of worsening OA outcomes with RFA, the pain relieving effects cannot be discounted as it is one of the most disruptive symptoms of OA. Therefore, effects of RFA on knee biomechanics and proprioception should be studied to understand the long-term impacts of this procedure.

In youth hockey the act of bodychecking is used to separate the opponent from possession of the puck by contacting the body. In one form or another bodychecking has been an integral part of hockey, especially competitive hockey. Bodychecking is associated with a high risk for concussion symptoms with a number of studies reporting a significant decrease in concussion symptom presentation when bodychecking is removed from the game (Black et al., 2016). To decrease the incidence of concussion symptom presentation and maintain body checking in the game, some leagues have introduced modified body contact rules. This study compared the brain trauma profiles, characterized by frequency and magnitude, of players playing with modified body contact rules to a standard bodychecking hockey league. U15 AAA adhered to standard bodychecking, while M15 minor only allowed shoulder-to-shoulder contact while keeping sticks on the ice and travelling in the same direction along the boards. 16 U15 AAA and 16 M15 minor hockey games were analyzed documenting head impacts, and head impact conditions that were reconstructed to examine the differences by comparing frequency and magnitudes of head impact events. There were 76 and 101 impacts in AAA and M15 minor, respectively. Most common events in AAA were head-to-glass, shoulder, and other; and in M15 minor were head-to-shoulder, head, and other. Magnitudes were grouped into very low, low, medium, high, and very high. The only magnitude levels that were significantly different when comparing total head impacts were more very low magnitude head impacts in M15 minor. Most common frequencies of magnitude levels for events in AAA were low glass, and in M15 minor were very low head, and low shoulder events. Changing the body contact rules increased the frequency of very low magnitude events and did not change the frequency of individual events between the medium and very high magnitude events. The low magnitude displayed a shift from head-to-glass to shoulder-to-head events when body contact rules were modified. These findings suggest that modifying body contact rules can result in differences in the frequencies and magnitudes of head impacts in U15 ice hockey. Changing body contact rules resulted in changes of most common events, though the frequency of magnitudes of brain trauma did not decrease with modified contact. It is important to understand the risks associated with the frequencies of events and magnitudes in both divisions.

Prostaglandins (PGs) are important signalling factors for bone mechanotransduction. The inhibition of cyclooxygenase, responsible for the synthesis of PGs, with non-steroidal anti-inflammatory drugs (NSAIDs) has been shown to influence bone formation induced by mechanical stimulation. The purpose of this study was to examine the timing effects of NSAID administration on: 1) bone formation induced by multiple mechanical loading events in a rat model and 2) the PGE2 response of MLO-Y4 osteocyte like cells stimulated by fluid shear stress. The rat forelimb compression model was used to induce bone formation in male and female rats using a 1-month loading protocol (12 loading sessions). The right forelimbs were loaded and the left forelimbs served as non-loaded controls. NSAIDs were administered orally either before or after loading. Fluorochrome labels were administered to the rats to determine mineral apposition rate (MAR). The NSAIDs examined (indomethacin, NS-398 and ibuprofen) did not significantly affect periosteal MAR, administered either before or after loading, suggesting NSAIDs do not affect bone adaptation to multiple mechanical loading events. To examine in vitro effects of NSAIDs on PGE2 production, an orbital shaker was used to apply fluid shear stress to MLO-Y4 cells seeded in 6-well culture plates. Indomethacin was added to the culture media either before or after loading and media PGE2 concentrations were determined at various time points by enzyme immunoassay. Fluid shear stress increased PGE2 production of MLO-Y4 cells and indomethacin administration inhibited that response when administered both before and after fluid flow. However, PGE2 production was influenced by the media changes that occurred in the in vitro experiments, making it difficult to differentiate between indomethacin effects and media change effects. The in vitro experiments revealed the difficulties of modeling the timing effects of NSAID administration on MLO-Y4 PGE2 production in response to fluid flow. / Thesis / Doctor of Philosophy (PhD) / Bone is a dynamic tissue that can adapt to mechanical loading. Prostaglandins (PGs) are important signalling factors produced by osteocytes, the bone mechanosensing cells, that help to activate various cells and cell processes leading to changes in bone structure. Blocking PG signalling with non-steroidal anti-inflammatory drugs (NSAIDs) has been shown to influence bone formation induced by mechanical stimulation in animals and humans. The purpose of this study was to examine the timing effects of NSAID administration on: 1) bone formation induced by multiple mechanical loading events in rats and 2) the PG production of osteocyte like cells in response to fluid flow stimulation. The results of this study suggest that NSAIDs, administered either before or after loading, do not affect bone responses to multiple mechanical loading events. Further investigation is needed to determine the translatability of these findings to NSAID use around the time of exercise in humans.

Passive exoskeletons hold promise in reducing the risk of work-related musculoskeletal disorders, however further research is essential before widespread adoption can occur. This study explores the feasibility of using subjective measures of physical demand in place of costly and less practical objective measures. Normalized electromyography (nEMG) data and ratings of perceived exertion (RPE) were collected from seven different studies conducted by the Occupational Ergonomics and Biomechanics Lab (OEB lab). Employing a repeated measures three-way ANOVA, we assessed the influence of nEMG, gender, and exoskeleton type on RPE. Additionally, mean nEMG and RPE from seven passive exoskeleton-based studies conducted outside the OEB lab were assessed in order to determine if the findings from the OEB lab existed across other research environments. The results demonstrated a general positive linear trend between nEMG and RPE for both the individual and mean results. Substantial inconsistencies emerged when considering the influence of gender, exoskeleton type, and task conditions on the relationship between nEMG and RPE. These discrepancies underscore the need for more in-depth research into this topic, specifically investigating the effects of gender and exoskeleton design. / Master of Science / Passive exoskeletons, devices designed to improve safety and provide support to the body, offer the potential for reducing muscle strain and reducing work-related injury risk. However, before these devices can be widely adopted, more research is necessary. Subjective measures of exertion, an affordable and user-friendly alternative to objective measures, require further investigation before replacing traditional methods in exoskeleton research. This study explores the possible connection between subjective and objective assessments of physical demand during passive exoskeleton usage. We analyzed data from seven studies conducted by the Occupational Ergonomics and Biomechanics Lab (OEB lab), focusing on muscle activity (an objective measure) and perceived exertion (a subjective measure). Our analysis examined the relationship between these objective and subjective measures, as well as how gender, exoskeleton type, and task conditions influenced this relationship. Additionally, we considered mean values from seven passive exoskeleton studies conducted outside the OEB lab, to investigate whether our findings existed in other research environments. The results revealed that as muscle activity increased, perceived exertion tended to increase as well. Moreover, our findings demonstrated that gender, exoskeleton type, and task conditions did influence the relationship, although there was significant variability in how these factors affected it. This research sheds light on the potential for using subjective measures in exoskeleton studies, bringing us closer to making exoskeletons more practical and accessible for real-world applications while acknowledging the complexities of this relationship.

<p>In community mobility, walking is commonly completed with other concurrent tasks, described as locomotor multitasks. Many locomotor multitasks rely on vision for both gait and concurrent tasks. When each of the individual tasks uses the same perceptual modality (e.g. vision), structural interference occurs. Structural interference is different from capacity interference, which refers to tasks competing for limited cognitive resources. While locomotor multitask studies have demonstrated that completing the locomotor multitask typically leads to performance impairment in gait and/or the concurrent task, the wide range of tasks has confounded the ability to fully understand how structural and capacity interference affect multitask performance. Thus, the purpose of this dissertation was to delineate how structural interference (Study 1) and capacity interference (Study 2) affect gait multitask performance. To facilitate comparison across studies, the two studies (Study 1 and Study 2) in this dissertation used the same gait task – obstacle crossing – and the same cognitive task – a visual discrete reaction time (RT) task. A discrete RT task was completed while approaching to an obstacle, where visual information regarding obstacle is being gathered to plan for the successful obstacle crossing. In Study 1, to determine if structural interference affects performance impairment in young and older adults, gaze diversion was manipulated by the RT task location (gaze diverted to the obstacle, and gaze diverted away from the obstacle). The RT task was also completed while standing to strengthen the interpretation that any performance impairments were due to structural interference. Study 1 results indicated that structural interference affects both gait and cognitive task performance. Structural interference demonstrated performance impairments in both young and older adults, but the strategies were different. Young adults were more likely adopt gait behavior that increased the risk of tripping when gaze was diverted away from the obstacle (high structural interference), but older adults demonstrated a strategy that decreased the risk of trip when gaze was diverted to the obstacle (low structural interference). This finding highlights the critical role of vision in adaptive gait. In study 2, to determine if capacity interference affects performance impairment in young adults, both gait and cognitive task were manipulated while structural interference was held constant; gait task was manipulated by obstacle height (level walking, 15% leg length height, and 30% leg length height obstacle), and cognitive tasks were three RT tasks (Simple RT, Choice RT, Simon RT). The baseline for each gait task (without RT task) and cognitive task (while seating) was also measured. Capacity interference demonstrated that task prioritization strategy was different for gait challenge versus cognitive challenge in young adults. As gait task difficulty increased, gait task was prioritized. Conversely, as cognitive task difficulty increased, cognitive task was prioritized. This finding highlights that young adults have the ability to flexibly allocate the resources to accomplish the multitask. Lastly, an interesting finding from two studies (Study 1 and Study 2) was when interference is applied during the planning phase – during the approach to the obstacle – structural interference has a greater effect on obstacle crossing performance than capacity interference.</p>

Subconcussions in sport is a growing field of interest and concern as deteriorative effects of these impacts have been shown in athletes without a diagnosed concussion. Detecting subconcussions is extremely difficult and there is no standardized method to recognize these injuries. A first step in identifying subconcussion is taking a closer look at concussions. The vestibular system has been shown to be negatively affected after concussive injuries which can be quantified via oculomotor function and pupillometry. Currently, King Devick (KD) style tests and Pupillary Light Reflex (PLR) are two popular tests that can be administered to athletes to gather clinical eye measures relating to oculomotor function and pupillometry. This study aimed to investigate how clinical eye measures change through serial in-season testing of Division 1 (D1) soccer athletes. Head impacts throughout a soccer season were recorded and we hypothesized that a greater number of head impacts would result in negative clinical changes even in the absence of a diagnosed concussion. No major trends were observed in soccer athletes that can be associated with trends seen in concussed populations. Soccer athletes were found to be slightly more likely to test abnormally than non-contact controls and soccer athletes with a greater number of head impacts were found to have slightly more abnormal tests than athletes with fewer head impacts. Overall, this study provides a dataset of pre and post-season measurements and uniquely includes multiple in-season measurements to provide a new perspective on oculomotor function and pupillary light reflex over the course of a sports season. / Master of Science / Subconcussions in sport is a growing field of interest and concern as deteriorative effects of these impacts have been shown in athletes without a diagnosed concussion. Detecting subconcussions is extremely difficult and there is no standardized method to recognize these injuries. The first step at identifying subconcussions is to more closely look at concussions. Eye movements and pupil response to stimuli can be affected after a concussive injury. Currently, King Devick (KD) style tests and Pupillary Light Reflex (PLR) are two popular tests that can be administered to athletes to gather clinical eye measures relating to eye motion and pupil response to stimuli. This study aimed to investigate how clinical eye measures change through repeated in-season testing of Division 1 (D1) soccer athletes. Head impacts throughout a soccer season were recorded and we hypothesized that a greater number of head impacts would result in negative clinical changes even in the absence of a diagnosed concussion. No major trends were observed in soccer athletes that can be associated with trends seen in concussed populations. Soccer athletes were found to be slightly more likely to test abnormally than non-contact controls and soccer athletes with a greater number of head impacts were found to have slightly more abnormal tests than athletes with fewer head impacts. Overall, this study provides a dataset of pre and post-season measurements and uniquely includes multiple in-season measurements to provide a new perspective on clinical eye measures over the course of a sports season.

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