Thesis (Ed. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 134-138). Also available via the Internet.

University of Macau / Faculty of Science and Technology / Department of Electrical and Computer Engineering

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The purpose of this study was to examine the effects of training for competitive rowing on cardiovascular condition as measured by the brachial pulse wave (Cameron Heartometer). Brachial pulse wave records were taken on fifteen male subjects (nine varsity and six freshmen rowers) every week over a ten week period. Measurements of fourteen variables were obtained from each individual brachial pulse wave record. The data for each subject consisted of 10 serial measurements for each of 14 brachial pulse wave variables. There were thus 14 variables for each of 15 subjects, giving 210 sets of variables in total. Each of these sets was tested for linearity of regression against number of days elapsed from the beginning of the ten weeks testing period to the time when the pulse wave record was made. As a means of determining relative cardiovascular condition of rowers during training, mean measurements for twelve brachial pulse wave variables of (a) varsity and (b) freshmen crew members were compared with corresponding mean measurements for four non-rowing athletic groups. The brachial pulse wave tracings obtained during the training period suggest that progressive changes in the variables studied were, on the whole, relatively small and unstable. The data suggest that heart rate - blood pressure measurements are fairly sensitive variables in reflecting the effects of training but other measurements of the brachial pulse wave are not. Comparison of the rower's measurements with those of other athletic groups showed that varsity rowers were superior in cardiovascular condition to freshmen rowers before during and after training and that both groups were in many respects superior in cardiovascular condition to other non-rowing athletic groups. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

By superimposing an artificial water flow over the gills out of phase with the natural breathing movements of the fish, it has been possible to demonstrate that bradycardia and cardiorespiratory synchrony develop in response to decreased peripheral oxygen levels. Further evidence that peripheral and not central receptors are involved was furnished by injecting deoxygenated blood into the dorsal aorta; no effect on heart rate or breathing was observed. Bradycardia still develops in response to hypoxia at the respiratory surface even during the absence of branchial blood flow demonstrating that the circulatory system is not involved in this reflex. Numerous tastebud-like receptors have been found lining the anterior faces of the gill bars. These are innervated by the branchial branches of the vagus nerve. Stimulation of the cut central ends of these nerves results in responses similar to those obtained when environmental oxygen levels are decreased. It is suggested that these tastebud-like organs are the receptors and that the branchial branches of the vagus nerve form one afferent pathway for reflex bradycardia and cardiorespiratory synchrony. Other possible afferent pathways are suggested and the functional significance of the reflex is discussed. / Science, Faculty of / Zoology, Department of / Graduate

Social support has been associated with reduced mortality and morbidity from a number of causes. To assess possible mechanisms of action relating to cardiovascular (CV) responsiveness, 90 male and female university students delivered a five-minute speech on a controversial topic to a same-sex laboratory confederate. Subjects were randomly assigned to one of three conditions in which the confederate either (a) agreed with the subject, (b) remained impassive (neutral), or (c) disagreed with the subject. Blood pressure (SBP and DBP) and heart rate (HR.) were monitored throughout the experiment. Self-report measures of state self-esteem and affective state were taken pre- and post-task, and reactions to the task were assessed with post-task self-report measures. Subjects reported strong differences in supportiveness of the confederate in the three conditions. Self-report data indicated increase in arousal during the speech (a finding synchronous with CV data), and they reported the Disagree condition to be less pleasant than the Agree condition. CV data were analyzed as a 2 x 3 (sex by experimental condition) repeated measures ANOVA assessing changes from baseline to speech task. Sex differences on CV measures matched patterns generally reported: Men had higher SBP and lower HR than women. All CV measures increased significantly and substantially during the speech task. HR was higher in the Disagree and Neutral conditions than in the Agree condition. SBP and DBP did not differ by condition. There were no sex by condition interactions; however, there was a trend towards men’s HR increasing more in the neutral condition and women’ more in the disagree condition. These data partially support earlier findings in similar experiments while suggesting that subtleties of context, task selection, and content of supportive interaction may have significant impact on the degree to which social support attenuates CV response to social stressors. Unanswered questions for future research are delineated, and implications for designing and implementing interventions that enhance social support are discussed. / Arts, Faculty of / Psychology, Department of / Graduate

In the field of process control it is desirable to study dynamic characteristics such as frequency response and distortion when determining just how equipment is to be controlled. Pneumatic controllers, transmitters, control valves, etc., all have dynamic behaviors which can be expressed mathematically as transfer functions. Each component plays an important role in determining the entire system behavior. Frequency response is one technique used in developing a component’s transfer function. By driving a device with a sinusoidal signal of fixed amplitude and frequency the output amplitude and phase shift are measured and compared with that of the input. Varying the frequency of the input at a fixed amplitude generates frequency response data which identify the device’s dynamic behavior.

Recent years have witnessed an increasing trend for people in the medical and engineering professions to couple their talents in a more united effort to better understand the functioning of the human body. This union of technologies has meant the introduction of new viewpoints and techniques in the field of physiological research. The engineers' basic tool, mathematical modeling, has perhaps been one of the most noticeable additions. There has been a significant amount of work done in recent years along these lines of deriving mathematical models to express the functioning of a subsystem of the body, and then, using analog, digital, or hybrid computers, analyzing the system through its model representation. Apparently, however, the latest modeling techniques, namely bondgraph concepts and computerized model parameter identification, have not been utilized in this physiological research effort. The purpose of this work is to investigate the feasibility of applying bondgraph and computerized model parameter identification techniques to physiological research.