Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

published_or_final_version / Molecular Biology / Doctoral / Doctor of Philosophy

The hypothesis in this dissertation is that the mathematical and physiological models can be developed to estimate cardiac output and metabolic demand of exercising individual from simple non-invasive physiological parameters such as heart rate, respiration, working rate and body movement (using multiple triaxial accelerometers). The models developed could be incorporated as part of a closed loop control system for cardiac pacemaker and/or heart assist devices. A reliable measurement system has been developed to measure cardiac output, heart rate, body movement and respiratory variables and to process and analyze the data coming from the measurements. Analyzing, designing and modelling of the measurement system have also been conducted. The foremost is to model the mixing chamber based gas measurement system and the other is to analyze and compensate the orientation error of triaxial accelerometers on the assessment of energy expenditure. Two mathematical models and one physiological model have been developed in the current research. The first mathematical model is to estimate steady state energy expenditure using a nonlinear regression method from the outputs of triaxial accelerometers. Results show that the proposed nonlinear model is better than both the traditional linear models and the earlier nonlinear models. The second mathematical model emphasizes on investigating the key central cardiovascular response to the steady state of incremental exercise. The modeling results show that all the studied cardiovascular parameters response to exercise nonlinearly except heart rate which responses to exercise linearly. Furthermore, based on a previous model developed in the Biomedical Systems Laboratories in UNSW and the reliable experimental data, a physiological model has been established to successfully estimate both the cardiac output and the metabolic demand with heart rate and workload as its input.

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

This study investigated the differences in the cardiovascular reactivity (CVR: HR, SBP, DBP) of trained and untrained individuals who performed the cold pressor test (CPT) after exercising for 30 minutes at 70% VO₂ max and participating in an attention control. Eighteen untrained and eleven trained males were randomly assigned to a treatment sequence. The subjects performed either 30 minutes of cycling at 70% VO₂ max Or an attention control. Following 48 hours, the other activity was performed. The CPT followed 1 hour after each treatment session. Rest, peak, and recovery measurements were acquired. Examination of trained and untrained group means, regardless of condition, indicated that trained subjects had lower HR measurements at rest (F_1,25 = 6.86, p < .05) and peak (F_1,25 = 6.33, p < .05). Closer examination of the different effects due to the acute exercise and control conditions regardless of training state did not reveal any beneficial effects due to the exercise bout. In addition, this study did not support differences in CVR to the CPT due to an interaction of acute exercise with the trained and untrained states of individuals. Resting measures did reveal reduced DBP (F_1,25 = 4.06, p < .05) and HR (F_1,25 = 3.19, p = .09) in trained subjects compared with the untrained following the exercise session indicating a beneficial reduction in the anticipatory response to the stressor. This study did not statistically support the effectiveness of 30 minutes of exercise at 70% VO₂ max or advantages of a physically trained state in reducing CVR to the CPT. In addition, this study did not support the effectiveness of the interaction of exercise at 70% VO₂ max with the trained or untrained state in reducing CVR to the CPT. / Master of Science

This investigation assessed the effects of acute aerobic exercise (AE) on cardiovascular reactivity (CVR) to a non-exercise stressor. Nineteen untrained, healthy male volunteers were stratified on diastolic blood pressure (DBP) response to the cold pressor test (CPT), then randomly assigned to either a minimal exercise condition (5 min of freewheel cycling) or 30 min of exercise on a bicycle ergometer at 55-60% V02max. Heart rate (HR) and BP were monitored during the resting, arousal, and recovery phases of the CPT at 1 hr, 3 hr, and 24 hr post-exercise. Results revealed statistically non-significant response and recovery effects; however, two important trends emerged. The 30 minute exercise group exhibited a tendency toward a reduced DBP response to the CPT during the 1 hour post-exercise session (p=0.08) and SBP response to the CPT was lower in the 30 minute exercise group at 3 hours post-exercise (p=0.08). These findings provide only minimal support for the effectiveness of 30 minutes of AE at 55-60% V02max in attenuating physiological response to the CPT in untrained males. / Master of Science

Abstract not available

[Truncated abstract] Cardiovascular reflex control of the vasculature is important in maintaining adequate tissue oxygenation in the face of disturbances in physiological homeostasis. Alterations in blood oxygen levels and blood distribution evoke integrated neural, mechanical and humoral responses which modulate peripheral vasomotor tone to maintain systemic cardiovascular integrity. The balance between the local effects of hypoxia and changes in chemoreflex control of vascular tone during hypoxia determine whether net vasoconstriction or vasodilatation is evident in the peripheral vasculature. The mechanisms contributing to hypoxic vasodilatation per se have not previously been defined in healthy humans. Study 1 of this thesis (Chapter 3) investigated the mechanisms contributing to vasomotor responses to chemoreflex activation in the human forearm ... Study 2 (Chapter 4a) investigated the mechanisms controlling vasomotor responses to isocapnic hypoxia in subjects with type 2 diabetes ... Study 3 (Chapter 5) compared the vascular responses to decreased venous return in individuals with and without right atrial afferent innervation ... The results of this thesis indicate that in healthy humans isocapnic hypoxia induces sympathetic vasoconstriction, which masks underlying β-adrenoceptor mediated vasodilatation. The normal vasomotor response to isocapnic hypoxia is impaired in subjects with type 2 diabetes. Despite intact vasoconstrictor responses, subjects with type 2 diabetes exhibited attenuated adrenaline-mediated vasodilatation compared to healthy control subjects, suggesting that the chemoreflex in these subjects is ill-equipped to respond to hypoxic stress. In clinical terms, impaired reflex vasomotor

The primary purpose of this study was to investigate the effect of acute high-intensity interval exercise (HIIE) vs. continuous moderate-intensity exercise (CME) on serum CTRP9 and brachial FMD responses in obese and normal-weight subjects. Sixteen participants (9 obese and 7 normal-weight) completed HIIE and CME in a randomized fashion. Our results showed a significant time effect for CTRP9 immediately following acute HIIE and CME in both groups. Furthermore, both significant treatment by time and group by time interactions for FMD were observed following both exercise protocols, with greater CME-induced FMD response in obese subjects than normal-weight subjects. Additionally, a positive correlation in percent change (baseline to peak) between CTRP9 and FMD was observed following acute CME. These findings support acute CME for improvement of endothelial function in obesity. Furthermore, the novel results from this study provide a foundation for additional examination of the mechanisms of exercise-mediated CTRP9 on endothelial function. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Al hoe meer organisasies in Suid-Afrika gaan tans deur 'n herstruktureringsfase wat meebring dat die totale werksmilieu verander. Die werknemer verkeer onder druk om aan die nuwe eise in die wereld van werk te voldoen. Druk om te presteer en werksuitset te !ewer mag disfunksionele stres en antler psigiese probleme meebring. Organisasies speel 'n belangrike rol in die dinamiese groeiproses van die individuele werknemer en raak toenemend bewus van die werknemer se fisiese en psigiese gesondheid. Talle organisasies het reeds korporatiewe gimnasiums opgerig en sommige bied subsidiering van lidmaatskap aan gesondheidsklubs aan hul werknemers. Sekere mediese skemas begin self gesondheidsplanne ontwerp met behulp van gesondheidsklubs om die gesondheid van die werknemer te bevorder. / M.A. (Bedryfsielkunde)