Effects of aerobic exercise training on arterial stiffness and autonomic function in obese adults at-risk of cardiovascular disease and type 2 diabetes

Abstract

Obesity is a major risk factor for cardiovascular disease (CVD), CVD mortality, and type 2 diabetes. Arterial stiffness and autonomic dysfunction are independent predictors of CVD and type 2 diabetes. Moreover, African Americans (AA) have a disproportionate prevalence of elevated arterial stiffness compared to Caucasians. Obese individuals have a greater prevalence of diminished autonomic nervous system activity compared to lean individuals. Despite evidence of aerobic exercise training benefiting arterial stiffness and autonomic dysfunction in the general population, optimal intensity and volume for AAs and obese individuals remain unclear. The purpose of this dissertation was to determine whether high-intensity aerobic exercise training improved arterial stiffness and aortic compliance to a greater degree than moderate intensity in obese AAs (study 1), if clinically significant weight loss from a combined hypocaloric diet and aerobic exercise intervention increases heart rate variability (HRV) in obese adults and to evaluate the impact of aerobic exercise volume on HRV during weight maintenance (study 2). Arterial stiffness or aortic compliance did not improve in response to 24 weeks of moderate- or high-intensity, supervised aerobic exercise training at a volume consistent with public health guidelines. However, both groups significantly increased cardiorespiratory fitness compared to the control group. In addition, we observed an inverse relationship between changes in cardiorespiratory fitness and aortic compliance. The results from this study suggest AAs may require greater volumes of weekly aerobic exercise than recommended for the general population to improve arterial stiffness. The 10-week, combined intervention improved major HRV indices of parasympathetic activity. The changes in parasympathetic activity were inversely associated with fasting insulin concentrations. Both groups retained all HRV benefits over the 18-week maintenance phase. The results from this study suggest weight loss via energy restriction and exercise alter autonomic function, leading to improved sympathovagal balance in obese adults, also exercise volumes consistent with physical activity guidelines maintains improvements in autonomic function from weight loss. Collectively, the results of this dissertation provide valuable public health insight for health professionals prescribing aerobic exercise to improve predictors of CVD and type 2 diabetes, specifically arterial stiffness, aortic compliance, and autonomic dysfunction in at-risk, obese adults.