Master of Science / Department of Kinesiology / Craig A. Harms / In comparison to adults and adolescents, relatively little is known about ventilatory responses of prepubescent children to exercise. Children have smaller airways relative to lung size than adults and ventilate "out of proportion" to metabolic demands of exercise which may render them more susceptible to ventilatory limitations during exercise. It is also not known if there are any sex differences in ventilatory limitations during incremental exercise in children. Therefore, the purpose of this study was to determine the prevalence of ventilatory constraints (expiratory flow limitation, EFL) during incremental exercise to exhaustion in prepubescent (Tanner stage 1) boys and girls. Forty healthy, prepubescent boys (n = 20) and girls (n = 20) with no history of asthma completed baseline pulmonary function and lung volume tests. Subjects then completed an incremental cycle VO[subscript]2max test where workload was increased 10W every 90 sec until exhaustion. RPE, dyspnea ratings, and % EFL were recorded at the end of each exercise stage. EFL was determined by placing the exercising tidal volume loop inside a post-exercise maximal flow volume envelope. Ventilatory and metabolic data were recorded on a breath by breath basis throughout exercise via a metabolic cart. Arterial oxygen saturation was determined via pulse oximetry. Body composition was determined using dual-energy x-ray absorptiometry. Following 15 minutes of recovery, subjects exercised at 105% of their VO[subscript]2max workload until exhaustion to provide confident in the VO[subscript]2max measurement. There were no differences (p>0.05) in anthropometric measures (height, weight) or body composition (lean body mass, percent body fat) measures between boys and girls. At rest, boys had significantly higher lung volumes (TLC, boys = 2.6 + 0.5 L, girls = 2.1 + 0.5 L; FRC, boys = 0.9 + 0.3 L, girls = 0.7 + 0.3 L) and maximal flows (FVC, boys = 2.2 + 0.3 L, girls = 1.9 + 0.4 L; PEF, boys = 3.6 + 0.7 L/sec, girls = 2.9 + 0.6 L/sec; FEV1, boys = 1.9 + 0.2 L/sec, girls = 1.6 + 0.3 L/sec). At maximal exercise, boys had significantly higher VO[subscript]2max (boys = 35.4 + 7.5 ml/kg/min, girls = 29.5 + 6.6 ml/kg/min; boys = 1.2 + 0.2 L/min, girls = 1.0 + 0.2 L/min), VE (boys = 49.8 + 8.8 L/min, girls = 41.2 U+U 8.3 L/min), and VCO[subscript]2 (boys = 1.2 + 0.2 L/min, girls = 0.9 + 0.2 L/min) compared to girls. There were no differences (p>0.05) in VE/VCO2 (boys = 41.1 + 3.9, girls = 43.4 + 5.5), PETCO2 (boys = 35.5 + 2.5 mmHg, girls = 35.7 + 3.2 mmHg) maximal HR (boys = 174.4 + 23.1 bpm; girls = 183.4 + 16.6 bpm), RER (boys = 1.04 + 0.05, 1.03 + 0.08), or SaO2 (boys = 96.7 + 3.4%, girls = 97.7 + 1.3%) which was maintained within 3% of baseline throughout exercise for all subjects. EFL during exercise was present in 19 of 20 boys and 18 of 20 girls. Severity of EFL at VO2max, as judged by % overlap of tidal volume with maximal flow volume envelope, was not different between genders at any time during exercise (at VO[subscript]2max: boys = 58 + 7%, girls = 43 + 8%). There was no significant association between % EFL at VO[subscript]2max and aerobic capacity or total lung volume. A significant relationship existed between % EFL at VO[subscript]2max and the change in end-expiratory lung volume from rest to maximal exercise in boys (r = 0.77) and girls (r = 0.75). In summary, our data suggests that ventilatory constraints in the form of expiratory flow limitation are highly and equally prevalent in prepubescent boys and girls from moderate to maximal exercise which likely leads to an increased work of breathing, but not to decreases in arterial oxygen saturation.

Doctor of Philosophy / Department of Anatomy and Physiology / Thomas J. Barstow / Peripheral arterial disease (PAD) is a manifestation of the systemic disease of atherosclerosis that results in arterial stenoses of the lower extremities. Patients with PAD demonstrate slowed dynamics of pulmonary oxygen uptake (VO2 kinetics) following the onset of exercise and a profound reduction in peak oxygen uptake and work capacity. However, whereas the primary pathophysiology of PAD results from the lower extremity hemodynamic limitation, there are abnormalities distal to the arterial stenoses in PAD-affected skeletal muscle that may also contribute to the impaired exercise responses. Thus, the potential contributions of abnormal muscle metabolism versus local circulatory defects in the PAD exercise impairment remains unclear. In this context, the purpose of the dissertation was to advance our understanding of the abnormal pulmonary VO2 kinetics in PAD and characterize the local muscle deoxygenation responses during the rest-exercise transition exercise in health and PAD. The present series of investigations were designed to: 1. localize the abnormal pulmonary VO2 kinetics in PAD to the affected lower extremities, 2. characterize the kinetics of calf muscle deoxygenation during walking in PAD and healthy subjects, 3. describe muscle deoxygenation kinetics in relation to exercise work rate and blood flow in PAD and health, and 4. evaluate the effect of arterial revascularization on pulmonary VO2 kinetics in PAD. These investigations revealed a persistent abnormality in muscle oxygen utilization in PAD-affected skeletal muscle that was not associated with the severity of hemodynamic compromise. In particular, we observed slowed pulmonary VO2 kinetics in PAD only during exercise of the PAD-affected skeletal muscles. Moreover, muscle deoxygenation kinetics following the onset of walking and lower intensity calf exercise were prolonged in PAD subjects while leg blood flow responses were normal. However, at higher work rates, PAD muscle deoxygenation kinetics accelerated, demonstrating a work rate and presumably blood flow dependence. Lastly, arterial revascularization tended to improve, but not consistently normalize, pulmonary VO2 kinetics in PAD subjects. Thus, these investigations demonstrate abnormal oxygen uptake kinetics in PAD and provide evidence that local abnormalities of the affected skeletal muscle may contribute to the abnormal VO2 kinetics and exercise intolerance of patients with PAD.

Policies are shaped by social values and assumptions, and can significantly impact the delivery of health and social services. Marginalized groups are often disadvantaged in the political realm and reliant on publicly funded services and supports. The purpose of this research is to consider how public policies are constructed and implemented for marginalized groups and to increase understanding of the consequences of policy reform. It draws on a case study of the Ontario Disability Support Program, Employment Supports (ODSP-ES) and considers the impact of the policy revision that occurred in 2006 on employment support services for people living with mental illness. A constructivist grounded theory approach guided data collection and analysis. Key policy documents were analyzed and 25 key informant interviews were conducted with individuals who were involved in: the construction and/or implementation of the policy; developing and/or delivering employment services under the policy; or advocacy work related to the policy. The findings highlight the impact of outcome-based funding on employment services and practices, and provide lessons for the construction and implementation of public policy for marginalized groups. The new funding system has promoted a shift from a traditional social service model of employment supports towards a marketing model, wherein services focus on increasing job placement and short-term job retention rates. However, the introduction of market principles into employment services has had significant implications for people living with mental illness. Employment programs are required to absorb increased financial risk, thereby altering the way service providers work with clients to help them find and keep jobs; there is a heightened focus on the rapid placement of clients into available jobs and less attention to the quality of employment being achieved and to complex barriers that prevent individuals from succeeding with employment. Although ODSP-ES has been somewhat successful at connecting people with disabilities to competitive employment, it has led to secondary consequences that compromise its overall utility. The findings highlight the complexity of constructing and implementing public policy for marginalized groups and suggest that evaluating public policy is an interpretative exercise that should be explored from multiple perspectives beyond the stated objectives.

Policies are shaped by social values and assumptions, and can significantly impact the delivery of health and social services. Marginalized groups are often disadvantaged in the political realm and reliant on publicly funded services and supports. The purpose of this research is to consider how public policies are constructed and implemented for marginalized groups and to increase understanding of the consequences of policy reform. It draws on a case study of the Ontario Disability Support Program, Employment Supports (ODSP-ES) and considers the impact of the policy revision that occurred in 2006 on employment support services for people living with mental illness. A constructivist grounded theory approach guided data collection and analysis. Key policy documents were analyzed and 25 key informant interviews were conducted with individuals who were involved in: the construction and/or implementation of the policy; developing and/or delivering employment services under the policy; or advocacy work related to the policy. The findings highlight the impact of outcome-based funding on employment services and practices, and provide lessons for the construction and implementation of public policy for marginalized groups. The new funding system has promoted a shift from a traditional social service model of employment supports towards a marketing model, wherein services focus on increasing job placement and short-term job retention rates. However, the introduction of market principles into employment services has had significant implications for people living with mental illness. Employment programs are required to absorb increased financial risk, thereby altering the way service providers work with clients to help them find and keep jobs; there is a heightened focus on the rapid placement of clients into available jobs and less attention to the quality of employment being achieved and to complex barriers that prevent individuals from succeeding with employment. Although ODSP-ES has been somewhat successful at connecting people with disabilities to competitive employment, it has led to secondary consequences that compromise its overall utility. The findings highlight the complexity of constructing and implementing public policy for marginalized groups and suggest that evaluating public policy is an interpretative exercise that should be explored from multiple perspectives beyond the stated objectives.