Obesity afflicts more than 30% of the U.S. population and is a major risk factor for the development of hypertension, type II diabetes, and cardiovascular disease. Studies in humans and animals indicate that obesity is associated with increased sympathetic outflow to the vasculature and kidneys. One mechanism postulated to underlie the increase in sympathetic nerve activity (SNA) in obesity is hyperinsulinemia. Little is known regarding the central circuitry underlying elevated SNA and arterial blood pressure (ABP) during hyperinsulinemia and obesity or if sympathoexcitatory circuits are still responsive to insulin in obesity. Hyperinsulinemic-euglycemic clamps elevate SNA to the hind limb vasculature in lean rodents but obesity is associated with resistance to the peripheral and anorexic effects of insulin. Therefore, the first aim was to determine whether diet-induced obesity causes development of insulin resistance in the central circuits mediating SNA. The sympathoexcitatory response to insulin was still intact in diet-induced obese rats indicating a role for insulin in the elevation in SNA and ABP in obesity. The second aim of this project was to identify the specific receptors in the rostral ventrolateral medulla (RVLM) that mediate the elevated SNA during hyperinsulinemia. The RVLM provides basal sympathetic tone and maintains baseline ABP. Glutamate is the major excitatory neurotransmitter and glutamate receptors of the RVLM are known to mediate multiple forms of hypertension. Blockade of RVLM NMDA-specific glutamatergic receptors reverses the increased lumbar SNA associated with hyperinsulinemia. In contrast, blockade of angiotensin II type 1 or melanocortin receptors in the RVLM had no effect on the sympathoexcitatory response to insulin. The goal of the third aim was to identify the cellular mechanisms within RVLM that mediate the elevated SNA and ABP in diet-induced obesity. Blockade of RVLM glutamate receptors reversed the elevated ABP and lumbar SNA associated with diet-induced obesity while it had no effect on rats on a low fat diet or those resistant to weight gain on the high fat diet. Similar to the findings during hyperinsulinemia, blockade of RVLM angiotensin II type 1 or melanocortin receptors had no effect on lumbar SNA or ABP during diet-induced obesity.

Discrete electrical stimulation of the organum vasculosum of the lamina terminalis (OVLT) produces sympathetically-mediated increases in peripheral resistance and arterial blood pressure (ABP). Since efferent fibers from the lamina terminalis innervate the kidney through polysynaptic connections, the present study determined whether electrical stimulation of the OVLT increased sympathetic outflow to the kidney. In anesthetized male, Sprague-Dawley rats (n=5) electrical stimulation of OVLT neurons produced frequency and current intensity dependent increases in renal sympathetic nerve activity (RSNA) and ABP that were abolished by ganglionic blockade with the nicotinic antagonist chlorisondamine (5mg/kg,i.v.). Since neurons from the OVLT terminate within the hypothalamic paraventricular nucleus (PVH), the present study also determined whether these connections mediate a portion of sympathetic and pressor responses to electrical stimulation of the OVLT. Bilateral inhibition of the PVH with the GABAA agonist muscimol (5mM/100nl) significantly attenuated the increase in ABP at all frequencies and current intensities. Spike-triggered averaging of RSNA revealed that PVH inhibition significantly blunted the RSNA responses to OVLT stimulation at 100, 200, but not 400andamp;igrave;A. The present findings indicate that electrical stimulation of the OVLT increases RSNA and ABP and that these responses are partially mediated by the tonic activity of PVH neurons.

Hypertension is one of the most common non-communicable diseases, and it is the leading cause of cardiovascular diseases, death and disability worldwide, especially in developing countries. Physical activity has been regarded as a commonly accepted modality for preventing and treating hypertension. However, despite its known benefits, this modality of treatment and prevention of hypertension continues to be underused. The present study aimed to determine the demographic, social and health-related factors that are associated with levels of physical activity participation among adults with hypertension in Kigali, Rwanda. This cross-sectional study was conducted with 252 adults with hypertension and 87 healthcare professionals through the Godin Leisure-Time Exercise Questionnaire (GLTEQ) and Physical Activity Exit Interview (PAEI). Two thirds of the participants (69.44%) were classified as sedentary. The following factors were found to be significantly (P<0.05) associated with the levels of physical activity: age, marital status, and level of education, residence, tobacco; past and current users, alcohol; current user, diabetes mellitus, BMI, perceived health status, self-efficacy, and blood pressure. None of the healthcare professionals were considered good physical activity counsellor. The findings of the present study highlight the need for the implementation of health promotion strategies aimed at promoting physical activity lifestyle among individuals with hypertension in Rwanda. Efforts should be made in educating people with hypertension on the benefits of integrating regular physical activity in their daily lives. Furthermore, healthcare professionals should be educated concerning how to promote physical activity to all patients especially those with hypertension. / Magister Scientiae - MSc

Peripheral arterial disease (PAD) is a common manifestation of stenoses and occlusions of the arteries of the lower extremities. Clinically, PAD is an important effect on functional ability, and quality of life because symptomatic patients are typically able to walk less than one to three blocks before rest is required.The double product break point (DPBP), also defined as the oxygen consumption at which the first portion of nonlinear increase in rate pressure product (systolic blood pressure X heart rate) begins has been identified to determine the anaerobic threshold during exercise test. The purpose of this study was to determine whether the DPBP could be detected in patients with PAD during a symptom-limited GXT on the motor-driven treadmill. Six male subjects (68.2 ± 6.5 yrs) with history of diagnosis of PAD participated in this study. Double product (DP) was assessed every 15 seconds during the test via the Kyokko Bussan CM-4001 automated blood pressure unit. The DPBP and VT were determined visually by three blinded observers. The mean values of Peak V02 and maximal heart rate were 19.4 ± 5.8 (ml/kg/min) and 130 ± 13 (bpm), respectively. In 4 of the six exercise tests in the present study, the DPBP and the VT were determined. The mean V02 at the DPBP and the VT were 15.7 ± 2.6 ml/kg/min and 14.2 ± 0.6 ml/kg/min, corresponding to 73 ± 7.2 and 74.5 ± 5.4 % respectively. In 3 of the six exercise tests both of the DPBP and VT were determined. The Mean V02 at the DPBP and VT were 14.6 ± 1.8 and 14.3 ± 0.7, respectively. The difference of the mean VO2 at the VT and DPBP was -.0.33 ml/kg/min.In conclusion, the results of the present study suggest that the DPBP can be identified and used as a useful marker to determine the functional performance in PAD patients. Walking time or distance measurement depends on the patient's perception of the pain. Thus, this study provides an objective way to appraise the functional performance and therapeutic results obtained from the exercise training in PAD patients, and provides a reference for exercise prescription for this population. / School of Physical Education

Access to abstract permanently restricted to Ball State community only / Access to thesis permanently restricted to Ball State community only / School of Physical Education, Sport, and Exercise Science

Hypertension afflicts one in four American adults and is a major risk factor for cardiovascular disease. Studies have shown that a family history of hypertension is an important predictor of future hypertension. Two hemodynamic factors control blood pressure (BP); cardiac output (CO) and total peripheral resistance (TPR). Although children of hypertensive parents may exhibit normal levels of these hemodynamic variables at rest, the response of these variables during exercise stress may differ. Therefore, the present study was designed to investigate whether children with a positive family history of hypertension exhibit an exaggerated BP response due to either an increased CO or an attenuated decrease in TPR during dynamic submaximal exercise compared to children of normotensive parents. Eleven children 12.2 ± 1.8 yr (M ± SE) of normotensive parents and 11 children 12.0 ± 2.4 yr of at least one hypertensive parent completed an orientation session, graded maximal cycle ergometer test, and a submaximal exercise bout consisting of 6 minutes of steady state cycling at 50 and 80% of maximal heart rate reserve. Blood pressure, CO and TPR were measured during the last 3 minutes of each submaximal exercise stage. An independent t-test was used to determine differences in the resting measures. The changes in TPR, BP and CO from rest through 80% intensity stage were examined using a twoway (group x intensity) ANOVA. The groups were evenly matched for age, weight, height, and body fatness. The children with a positive family history of hypertension had significantly higher resting systolic BP, diastolic BP (DBP), and mean arterial pressure (MAP) (p<0.05) compared to those children with a negative family history. Although there were no significant interactions among any of the variables studied, there was a tendency for TPR to be higher (p>0.05) at rest and throughout exercise in the positive history group. MAP and DBP were significantly higher in the positive family history group at rest and remained higher throughout exercise. In conclusion children of hypertensive parents exhibit a modest but significantly higher MAP and DBP at rest and during submaximal exercise. This subtle difference in BP control reflects an early trend toward increased TPR. / School of Physical Education

Healthcare practitioners, whom perform accurate sub-maximal exercise tests in healthy individuals, need to understand the physiological demands and normal cardiovascular (CV) responses with exercise. Exercise testing delivers valid information about the physiological systems of individuals that may identify healthy individuals at risk of developing future cardiovascular disease (CVD). Exercise is a common way to assess physiological stress experienced by an individual, because CV abnormalities that are not present at rest, can be elicited during exercise testing and be used to determine the adequacy of cardiac function. Cardiovascular markers like, resting heart rate (HR) and systolic blood pressure (SBP) have been used as simple non-invasive and useful biomarkers of the fundamental status of blood circulation and the CV system in healthy individuals. Studies have contributed to exercise under sub-maximal and maximal stress testing. Modern- day literature lacks information on the safe HR and SBP responses to an increase in workload during a sub-maximal exercise protocol in healthy individuals. Consequently, the first purpose of this study was to identify the current evidence in the literature on CV response during a sub-maximal incremental exercise protocol. Different protocols and modalities contribute to various CV responses over a wide age group and gender. Heart rate and SBP increases in a linear fashion with an increase in workload, irrespective of protocol and modality. The amount of this increase, or the response of these markers, is still a grey area in the literature, especially in healthy individuals. The second purpose of this study was to analyse the HR and SBP response in healthy adults during a sub-maximal incremental exercise test, with an increase in workload (watt). The systematic review found mean changes from baseline for HR and SBP to be 75.7% and 63.5% respectively, on bicycle protocols (N = 3). The treadmill protocols (N = 2) found similar mean changes from baseline of 113.3% for HR and 36.1% for SBP. Descriptive measures as well as Linear regression analyses were performed, using Generalised estimated equations (GEE). An independent t-test was used to compare the males with the female participants: HR and SBP response to an increase in workload (watt). GEE adjustments were made for age, body mass index (BMI) and workload (watt). Significant difference levels were set at p ≤ 0.05. The present once-off subject availability results revealed that male subjects were heavier and taller than their female counterparts (p ≤ 0.05). They also had a noteworthy higher SBPrest, as well as BMI (p ≤ 0.05). The results from the GEE analyses we presented prediction equation, with all variables significant, except for the BMI (p = 0.972 females; p = 0.169 males). In conclusion, the literature review indicated a lack of information on the HR and SBP response with workload in healthy adults. It is advised that further research is needed to test the prediction equations in healthy individuals to determine the validity and reliability. They need to be tested in a controlled clinical environment, where the participants are monitored more thoroughly. By putting these predicted equations to the test, healthcare practitioners will be able to identify an exaggerated HR and SBP response with an increase in workload. If the individual’s response is exaggerated, the healthcare practitioner can intervene to prevent future cardiovascular events. / Thesis (MSc (Biokinetics))--North-West University, Potchefstroom Campus, 2013

Healthcare practitioners, whom perform accurate sub-maximal exercise tests in healthy individuals, need to understand the physiological demands and normal cardiovascular (CV) responses with exercise. Exercise testing delivers valid information about the physiological systems of individuals that may identify healthy individuals at risk of developing future cardiovascular disease (CVD). Exercise is a common way to assess physiological stress experienced by an individual, because CV abnormalities that are not present at rest, can be elicited during exercise testing and be used to determine the adequacy of cardiac function. Cardiovascular markers like, resting heart rate (HR) and systolic blood pressure (SBP) have been used as simple non-invasive and useful biomarkers of the fundamental status of blood circulation and the CV system in healthy individuals. Studies have contributed to exercise under sub-maximal and maximal stress testing. Modern- day literature lacks information on the safe HR and SBP responses to an increase in workload during a sub-maximal exercise protocol in healthy individuals. Consequently, the first purpose of this study was to identify the current evidence in the literature on CV response during a sub-maximal incremental exercise protocol. Different protocols and modalities contribute to various CV responses over a wide age group and gender. Heart rate and SBP increases in a linear fashion with an increase in workload, irrespective of protocol and modality. The amount of this increase, or the response of these markers, is still a grey area in the literature, especially in healthy individuals. The second purpose of this study was to analyse the HR and SBP response in healthy adults during a sub-maximal incremental exercise test, with an increase in workload (watt). The systematic review found mean changes from baseline for HR and SBP to be 75.7% and 63.5% respectively, on bicycle protocols (N = 3). The treadmill protocols (N = 2) found similar mean changes from baseline of 113.3% for HR and 36.1% for SBP. Descriptive measures as well as Linear regression analyses were performed, using Generalised estimated equations (GEE). An independent t-test was used to compare the males with the female participants: HR and SBP response to an increase in workload (watt). GEE adjustments were made for age, body mass index (BMI) and workload (watt). Significant difference levels were set at p ≤ 0.05. The present once-off subject availability results revealed that male subjects were heavier and taller than their female counterparts (p ≤ 0.05). They also had a noteworthy higher SBPrest, as well as BMI (p ≤ 0.05). The results from the GEE analyses we presented prediction equation, with all variables significant, except for the BMI (p = 0.972 females; p = 0.169 males). In conclusion, the literature review indicated a lack of information on the HR and SBP response with workload in healthy adults. It is advised that further research is needed to test the prediction equations in healthy individuals to determine the validity and reliability. They need to be tested in a controlled clinical environment, where the participants are monitored more thoroughly. By putting these predicted equations to the test, healthcare practitioners will be able to identify an exaggerated HR and SBP response with an increase in workload. If the individual’s response is exaggerated, the healthcare practitioner can intervene to prevent future cardiovascular events. / Thesis (MSc (Biokinetics))--North-West University, Potchefstroom Campus, 2013

Despite pharmacological advances, exercise remains a cost effective preventative for cardiovascular disease (CVD) by acutely and chronically lowering systolic blood pressure (SBP). Although numerous studies have investigated aerobic and resistance training’s role in eliciting an acute SBP response termed post-exercise hypotension (PEH), few researchers have investigated how performing both cardiovascular and weight training in a single session (concurrent training) or how different prescriptions for order of exercise modality will elicit this PEH response; no known studies have attempted altering the order of exercise types within each session. This study seeks to determine if the order of exercise type will affect a PEH response following concurrent exercise. Participants (n=13), considered low risk for cardiovascular disease participated in a control session, graded exercise test (GXT) and two concurrent sessions, with concurrent sessions counterbalanced for order of exercise mode. Recovery SBP was analyzed in the laboratory for sixty minutes and for twenty-four hours thereafter using an ambulatory blood pressure monitor. All exercise conditions elicited a depression in SBP; however, only the cardiovascular-weight training (CVWT) concurrent session elicited PEH (p = 0.05). However, there were no differences in SBP attenuation between conditions. There was no main effect for PEH between conditions during twenty-four hour assessment. With no statistically significant differences in the magnitude of PEH twenty-four hours after exercise, it may be determined that the order of exercise does not vi affect the preventative attributes of aerobic and resistance exercise in regards to acute SBP response. Furthermore, only exercise involving resistance training (CVWT) provoked PEH during the first 60 minutes; therefore it may be argued that individuals should pair cardiovascular exercise with weight training in order to elicit the greatest cardiovascular benefits. Future studies should consider evaluating the effect of time of day and PEH following concurrent exercise to determine if pairing exercise modalities will at different times will affect the blood pressure response.

Thesis (Ph.D. (Human Movement Science))--North-West University, Potchefstroom Campus, 2010.