Date of Award

2015

Document Type

Open Access Dissertation

Department

Exercise Science

First Advisor

Steven N. Blair

Abstract

Cardiovascular (CV) diseases (CVDs) are known to be the leading cause of death globally, as CVDs account for the highest rate of mortality compared to any other causes. The mortality from CVDs, is projected to increase to nearly 23.3 million by 2030. Mortality number due to CVD in the United States is 600,000 per year, thus representing nearly 1 in every 4 deaths. Exercise blood pressure (BP) is an important marker of CV events that are associated with incident CV morbidity and mortality among individuals with or without any CVD at present. Elevated exercise BP among individuals with normal resting BP is a marker of incidence of hypertension and other CV events later in life. Cardiorespiratory fitness (CRF), body mass index (BMI) and body fatness are known predictors for CVD risk factors, morbidity, and mortality. It is important to examine how CRF, BMI and body fatness effect submaximal systolic blood pressure (SSBP). We therefore examined the independent and combined associations of CRF, BMI and body fatness with SSBP in young healthy adults.

This dissertation is comprised of three studies that were designed to 1) analyze the relation and trend of SSBP with CRF among young healthy men; 2) analyze the relation and trend of SSBP with body fatness among young healthy men; and 3) examine the association and trend displayed by SSBP with different levels of CRF and body fatness among young healthy women. Data used in these studies were drawn from the Energy Balance Study, an observational study done in Columbia, SC involving young healthy adults (N=430). We calculated body fat percentage (BF%) and fat mass index using total body fat (BF) measured by dual X-ray absorptiometry (DXA); BMI was calculated using the average of two height and two weight measurements. Graded exercise tests (GXT) using a Modified Bruce protocol on a motorized treadmill were used to measure CRF and SSBP was measured at each stage of GXT.

Study 1 found that a quadratic trend was evident between SSBP and CRF in a model adjusted for age, race, BF%, resting systolic blood pressure (SBP), alcohol intake and smoking, with the largest reduction in SSBP observed between men in Quintile (Q) 1 and 2. This is followed by a plateau at Q 3, and increase in the higher quintiles although still lower than Q 1.

Study 2 found that there was no significant change in SSBP with increase in weight and fatness from normal to overweight range but a significant rise with further increase in obese range at minutes 6, 8, and 10 (P<0.05 in most or borderline associations in few) after adjusting for age, race, resting SBP, alcohol intake, smoking, and CRF.

Study 3 found that CRF appeared to be independently associated with SSBP at the lower exercise intensities whereas, BMI at the higher intensities. BF% was not independently associated with SSBP at any intensity of exercise.

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