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The full abstract for this thesis is available in the body of the thesis, and will be available when the embargo expires.

For several decades biomechanical features of gait have been investigated for their relevance to musculoskeletal disease, particularly knee osteoarthritis. This is largely due to their established link between excessive or abnormally distributed ambulatory knee joint load and faster disease progression. Modifying aspects of gait kinematics, specifically the foot progression angle (FPA; a measure of in-toeing or out-toeing), can lower these joint loads and may be a tool for managing knee osteoarthritis. However, all the research both quantifying natural FPA and the work investigating how it can be modified, have relied on laboratory-based gait analysis which does not represent the typical walking environments people navigate in their daily life. In this dissertation we aimed to leverage innovative and clinically feasible technologies to move gait analysis and modification out of the laboratory and into the real-world. In the first study we demonstrated that the FPA can be measured with wearable technology both reliably and with acceptable accuracy compared to optical motion capture. We then identified the amount of gait data that needs to be collected in real-world settings to observe stable outcomes. Building from these initial studies, we performed the first characterization of the FPA in unsupervised, real-world settings over a week of community walking in a population with and without knee osteoarthritis. This showed the similarity between laboratory and real-world FPA magnitude but highlighted that laboratory measurements may underestimate the variability inherent in real-world walking. Lastly, we deployed a shoe-embedded sensor in the context of a gait modification clinical trial to monitor participants’ performance over time. This study also incorporated innovative methods, including a telerehabilitation delivery model, individualized gait modification, pre-screening for responders, and a self-directed gait modification magnitude. We found that delivering the intervention without any in-person guided practice still resulted in significant changes to the FPA, knee joint moments, and symptoms, warranting further investigation in a larger clinical trial. This dissertation demonstrated that real-world gait biomechanics can be collected with a single inertial sensor with sufficient precision to observe clinically meaningful changes, and it can be implemented in a clinical trial to monitor performance in ecologically valid environments.

Introduction: The etiology of running-related injuries is multifactorial, but it is accepted that biomechanical factors play a role. This thesis examined the influence of peak braking force on running-related injury risk and the effectiveness of a gait retraining program using real-time biofeedback to reduce this parameter in high-risk individuals.Methods: Healthy novice female recreational runners were recruited from the local running community. The studies in Chapters 2 and 3 were run in parallel, while the study described in Chapter 4 took place following their completion. Kinetic risk factors of running-related injury were examined using a prospective longitudinal cohort design and Cox proportional hazard models with competing risks were fit for each kinetic variable independently (Chapter 2). Baseline data were then analyzed to determine the kinematic correlates of kinetic risk factors using stepwise multiple linear regression to evaluate the amount of variance in each kinetic outcome explained by speed, foot strike angle, and kinematic variables associated with overstriding (Chapter 3). Finally, a similar but separate sample of female recreational runners considered to be at higher-risk of developing injury (peak braking force>0.27 BW) were enrolled in an eight-session gait retraining program using real-time biofeedback of the anterior-posterior (braking) ground reaction force (Chapter 4).Results: Peak braking force was associated with a five to eight-fold increased risk of running-related injury. Our findings suggest that the use of peak braking force may be a more effective target for gait retraining than vertical loading rate. Regression analysis of kinematic variables revealed that shortening step length and transitioning away from a rearfoot strike pattern are appropriate strategies to reduce peak braking force. An eight-session gait retraining program significantly reduced peak braking force, as well as vertical loading rates associated with running-related injury. This was achieved predominantly through a combination of increased step frequency and decreased step length.Conclusions: This dissertation provides new understanding of the role of kinetic risk factors—specifically peak braking force—in the development of running-related injury. Furthermore, it provides the structure for a larger randomized controlled trial to assess a gait retraining intervention to reduce peak braking force and running-related injury risk.

Pain is a common symptom in patients with chronic obstructive pulmonary disease (COPD). This symptom can negatively affect physical activity levels, quality of life, and health outcomes. It has been shown that systemic inflammation, comorbidities, and symptoms (e.g., dyspnea or fatigue) may cause pain. Although previous research has determined the association between pain and the presence of comorbidities, the specific comorbidities that cause pain and other etiologic factors of pain are still unknown. Also, the interrelationships among pain, dyspnea, and fatigue and whether the presence of one symptom accentuates another remain to be examined.The overall purpose of this dissertation was to investigate the etiology of pain by exploring the pain experience, the contributors to pain, the interrelationships between pain and other symptoms, and the associations between pain and thoracic abnormalities in patients with COPD. Studies I and II established the reliability and validity of the Brief Pain Inventory (BPI), Dyspnea Inventory (DI), and Brief Fatigue Inventory (BFI) in patients with COPD. Study III determined comorbidities that caused pain as well as compared pain, fatigue, and dyspnea symptomology in patients with COPD. This study utilized a cross-sectional survey design that included the BPI, DI, BFI, General Self-efficacy Scale, Clinical COPD Questionnaire, and Comorbidities/Medication Questionnaire. Study IV investigated chest computed tomography images of patients with COPD and current/ex-smokers to examine the associations between trunk pain and thoracic vertebral deformity and arthropathy. The findings showed that the BPI, DI, and BFI were reliable and valid questionnaires to evaluate symptoms in COPD. Similar to dyspnea and fatigue, pain was also a significant symptom in patients with COPD and these three symptoms were correlated with each other. Further, the most common comorbidities that caused pain were musculoskeletal diseases. Trunk pain in patients with COPD was associated with thoracic vertebral deformities, arthropathy of thoracic joints, and hyperkyphosis.In summary, pain in COPD is associated with musculoskeletal comorbidities and there are interactions between pain and other symptoms. This dissertation provides insight into the causes of pain in patients with COPD, which can facilitate the development of pain management strategies in COPD.

Introduction: Those with knee osteoarthritis report more falls than those without, and falls present serious economic, personal and public health consequences. Dynamic balance is an important factor associated with falls risk. Current clinical tests of balance in this population have limitations to their use. Further, interventions to improve dynamic balance have had mixed results in this population, possibly since more information on dynamic balancing ability is needed for better program design. This thesis examined the assessment and treatment of dynamic balancing ability in individuals with knee osteoarthritis.Methods: The Community Balance and Mobility Scale (CB&M), an advanced test of dynamic balance, was examined for use in individuals with knee osteoarthritis. The convergent validity, construct (known groups) validity, and test re-test reliability of the scale was assessed (Chapter 2). Convergent validity was assessed by comparing to tests measuring similar constructs, such as the Berg Balance Scale. Construct validity was assessed by comparing scoring of those with and without knee osteoarthritis. Test re-test reliability was assessed one week apart. Clinically modifiable factors associated with dynamic balancing ability were then investigated (Chapter 3). These included muscle strength, knee joint proprioception, knee joint range of motion and anticipatory postural control. Finally, a ten week dynamic balance training program, designed using findings from Chapter 2 and 3, was assessed in Chapter 4. This was a randomized controlled trial, with dynamic balancing ability and self-reported physical function measured at baseline and follow-up.Results: The CB&M was found to display moderate to strong convergent validity with other tests, strong construct validity and high test re-test reliability. Lower extremity strength, and to a lesser extent, knee range of motion were important factors associated with dynamic balancing ability. Ten weeks of training resulted in significant improvement in self-reported physical function but not in CB&M scores.Conclusion: This dissertation provides new understanding of dynamic balance assessment and treatment in those with knee osteoarthritis. These findings highlight a valid and reliable clinical outcome measure for dynamic balance, as well as provide insights into balance training program designed to improve outcomes and maintain high adherence in this population.

Mechanisms underpinning motor control of standing balance post-stroke remain unclear. Following stroke, ankle plantarflexor muscles demonstrate impairment associated with asymmetrical postural control and decreased balance. Stroke also results in increased attentional demands during challenges to standing balance. This thesis examined motor control impairment post-stroke from medial gastrocnemius motor units to the tri-muscle plantarflexor complex. Investigation of motor, kinematic and kinetic parameters of postural control during external perturbations in standing and associated levels of physiological arousal have furthered understanding of balance impairment post-stroke. Methods: Medial gastrocnemius motor units were recorded in controls (Chapter 2) and people post-stroke (Chapter 3) in standing as perturbations were sequentially applied at the pelvis under conditions of increased anteriorly-directed challenge. In both studies, motor unit firing rate was calculated during dynamic response to perturbation, and maintenance of steady state between perturbations. Joint kinematics, surface electromyography and movements of the centre of pressure were assessed. In Chapter 4, this methodology was expanded to cross-correlation analysis of electromyography activity of the three plantarflexor muscles with anterior-posterior centre of pressure during steady state. In Chapter 5, attentional demands surrounding timing of external perturbation were manipulated to investigate effects of stroke on physiological arousal and postural reactions.Results: In healthy subjects, medial gastrocnemius utilized primarily motor unit recruitment to maintain standing with a modest increase in motor unit firing rate only during the dynamic response to external perturbations. The paretic medial gastrocnemius also primarily used motor unit recruitment; however, lacked firing rate modulation during the dynamic response, albeit firing rate was related to kinematic variables of postural control. In people post-stroke, the three plantarflexors demonstrated asymmetrical motor control of postural sway between-legs but symmetry was improved under conditions of increased challenge to standing balance. Finally, knowledge of timing of perturbations did not decrease the heightened anticipatory postural strategy and level of physiological arousal exhibited post-stroke. Conclusions: This dissertation provides new understanding of motor control of standing balance post-stroke and reveals anticipatory postural strategies adopted post-stroke under conditions challenging balance. These findings implicate the importance of introducing challenge to standing balance post-stroke in the assessment and rehabilitation of postural control post-stroke.