Thesis (Ph. D.)--Florida State University, 2003. / Advisor: Dr. Robert J. Moffatt, Florida State University, College of Human Sciences, Dept. of Nutrition, Food and Exercise Sciences. Title and description from dissertation home page (viewed Sept. 15, 2005). Document formatted into pages; contains xi, 147 pages. Includes bibliographical references.

Thesis (M.Sc. (Clinical Pathology))--Mahidol University, 1982.

Background: Physical inactivity has been consistently associated with numerous negative health outcomes that track from childhood into adulthood, making physical activity a special concern in the pediatric population. Dose-response studies are particularly useful when trying to understand the minimal and optimal amounts of physical activity needed to reduce the risk of negative health outcomes. Unfortunately, previous work within youth has relied on self-reported measures of physical activity, and this research does not provide a clear picture of the true relation between physical activity and health. Objectives: Manuscript 1. Describe the dose-response relation between dyslipidemia and moderate-to-vigorous physical activity (MVPA) in youth. Manuscript 2. Quantify the difference between self-reported and objectively measured MVPA in youth. Taken together, the overall objective of this thesis was to examine the dose-response relation between objectively measured MVPA and dyslipidemia in youth and determine how this may affect current Canadian physical activity guidelines. Methods: Both manuscripts used data from the U.S. National Health and Nutrition Examination Survey. Fractional polynomial regression modeling was used to fit the dose-response curves between MVPA and lipid/lipoprotein measurements. Regression analysis as well as a Bland-Altman plot was used to explain the discrepancy between self-reported and objective measures of MVPA. All analyses were completed using SAS statistical software. Results: Manuscript 1. Risks for high-risk HDL-cholesterol and triglyceride values decreased in a curvilinear manner with increasing minutes of MVPA. The greatest reduction in risk occurred within the first 30 min/d of MVPA. The relation between level of MVPA and LDL-cholesterol was unclear. Manuscript 2. The average youth over-reported their MVPA by ~30 min/d. The over-reporting was not mediated by basic demographic factors; however, the difference in reporting was systematic in nature such that inactive youth over-reported to the greatest extent. Conclusions: Manuscript 1. Youth need to accumulate 30 min/d of MVPA to greatly reduce their risk for dyslipidemia. Manuscript 2. Youth tend to over-report their daily MVPA by approximately 30 min/d. Combined, the results from this thesis suggest that physical activity recommendations for cardiovascular health in youth should suggest a minimum of 30 min/d of MVPA and preferred level of 60 min/d. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2009-09-07 08:48:03.896

The thesis investigated the effect of exercise on endothelial function (measured as flow-mediated dilation (FMD)) and triacylglycerol concentrations following the ingestion of a high-fat breakfast and lunch in adolescent boys. The validity of measuring lipid and lipoprotein concentrations from a capillary blood sample, and the reproducibility of the postprandial FMD and triacylglycerol concentration responses to the high-fat meals, was established. The effects of prior continuous moderate-intensity exercise (60 min walking at 60% V̇O₂peak), repeated very short duration sprints (40 x 6 s maximal effort cycle sprints) and accumulated moderate-intensity exercise (6 x 10 min running at 70% V̇O₂peak) on endothelial function and triacylglycerol concentrations in adolescent boys were then established across three studies, each consisting of two, 2-day main trials (control and exercise). On day 1, participants were either inactive or completed the prescribed exercise. On day 2, FMD and triacylglycerol concentrations were measured prior to, and following, ingestion of a high-fat breakfast and lunch. In each control trial FMD was reduced (signifying endothelial dysfunction), compared to fasting, by 20-32% and 24-33% following the high-fat breakfast and lunch. Following continuous moderate-intensity exercise, repeated very-short duration sprints and accumulated moderate-intensity exercise these reductions were only 8% and 10% (main effect trial, P = 0.002; main effect time, P = 0.023; interaction effect trial x time, P = 0.088), 2% and 5% (main effect trial, P = 0.012; main effect time, P = 0.004; interaction effect trial x time, P = 0.003) and 1% and 3% (main effect trial, P = 0.020; main effect time, P < 0.001; interaction effect trial x time, P = 0.014) respectively. The continuous moderate-intensity exercise and repeated very short duration sprints also significantly reduced the total area under the triacylglycerol concentration versus time curve by 22% (Control vs. Exercise; 12.68 (sem 1.37) vs. 9.84 (sem 0.75) mmol L-1 6.5h, P = 0.018) and 13% (Exercise vs. Control: 8.65 (sem 0.97) vs. 9.92 (sem 1.16) mmol L-1 6.5h, P = 0.023). The accumulated moderate-intensity exercise also reduced the total area under the triacylglycerol concentration versus time curve by 11%, but this reduction was not significant (Control vs. Exercise: 10.71 (sem 0.94) vs. 9.56 (sem 0.67) mmol L-1 6.5h, respectively, P = 0.183). The experimental evidence from these studies emphasise that exercise might offer an acceptable, non-pharmacological means of influencing CHD risk when individuals are young. The results of these studies can help shape future physical activity guidelines.

Patients with kidney failure (KF) have a high incidence of cardiovascular (CV) disease, partly driven by insufficient clearance of uremic toxins. Recent investigations have questioned the accepted effects of adverse lipid profile and CV risk in uremic patients. Therefore, we related a panel of uremic toxins previously associated with CV morbidity/mortality to a full lipid profile in a large, tri-national, cross-sectional cohort. Total, high-density lipoprotein (HDL), non-HDL, lowdensity lipoprotein (LDL), and remnant cholesterol, as well as triglyceride, levels were associated with five uremic toxins in a cohort of 611 adult KF patients with adjustment for clinically relevant covariates and other patient-level variables. Univariate analyses revealed negative correlations of total, non-HDL, and LDL cholesterol with all investigated uremic toxins. Multivariate linear regression analyses confirmed independent, negative associations of phenylacetylglutamine with total, non-HDL, and LDL cholesterol, while indole-3 acetic acid associated with non-HDL and LDL cholesterol. Furthermore, trimethylamine-N-Oxide was independently and negatively associated with non-HDL cholesterol. Sensitivity analyses largely confirmed findings in the entire cohort. In conclusion, significant inverse associations between lipid profile and distinct uremic toxins in KF highlight the complexity of the uremic milieu, suggesting that not all uremic toxin interactions with conventional CV risk markers may be pathogenic.