Three studies were designed to investigate the effects of exercise-based lifestyle interventions including diet change and exercise training on cardiovascular and autonomic responses to various physical and mental challenges in untrained premenopausal women. In Study 1, the effects of different tasks designed to activate the sympathetic nervous system on autonomic control of cardiovascular functioning such as the Stroop colour-word task (Stroop) and lower body negative pressure (LBNP) in 20 untrained premenopausal women (22.6??0.7 years) were determined. In Study 2, a longitudinal exercise intervention strategy was used with 18 untrained premenopausal women (22.5??0.7 years) in order to investigate the effect of 15 weeks of high intensity intermittent exercise (HIIE) training on cardiac autonomic responses to mental challenge (Stroop) and LBNP. In Study 3, the effects of HIIE training combined with a Mediterranean-style eating plan and fish oil supplement (Fish oil, Exercise, Mediterranean diet; FEM) on cardiovascular function during mental challenge (Stroop) and physical tasks (handgrip and reactive hyperaemia) were examined in 32 overweight untrained premenopausal women (22.0??0.6 years). In these studies, forearm blood flow (FBF) was assessed using Hokanson Plethysmography with the venous occlusion technique. The surface electrocardiogram and continuous beat-to-beat arterial blood pressure were also monitored. Peak oxygen uptake was assessed using open-circuit spirometry (True Max 2400, ParvoMedics). In addition, body composition was measured using DEXA (dual energy X-ray absorptiometry; DPX-IQ, Lunar Radiation). Results from Study 1 indicate that FBF response to mental challenge in young females was smaller compared to previously obtained data from age-matched males. Furthermore, this FBF response to mental challenge was negatively correlated to insulin resistance estimated by the homeostasis model assessment (HOMA-IR) (r = - .52, p < .05). In addition, when cardiopulmonary baroreceptors were unloaded by a mild level of LBNP (-20 mmHg) during Stoop, FBF response to mental challenge (vasodilation) was abolished suggesting a large dependency of vasodilation response during mental challenge on cardiopulmonary baroreflex. After 15 weeks of supervised HIIE training, aerobic fitness improved (p < .05) whereas percent of body fat was significantly decreased (p < .05). In addition, recovery BP following Stroop was significantly reduced. Insulin resistance (HOMA-IR) was marginally decreased (p = .056). Women who had higher insulin resistance (HOMA-IR) lost less fat than women with lower HOMA-IR (r = .60, p = .088). In addition, change in FBF during Stroop after training was directly related to pretest insulin resistance levels (r = .68, p < .05). Therefore, HIIE training had a normalising effect on FBF response to mental challenge. PEP/LVET ratio at rest and during LBNP was also significantly increased in women with higher HOMA-IR suggesting a reduction in cardiac contractility via a decrease in sympathetic stimulation (r = .62, p = .076, r = .62, p = .75 respectively). In Study 3 results indicated that 12 weeks of the FEM trial significantly reduced percent of body fat (p < .001), fasting insulin (p < .05), interleukin-6 (p < .05) and cortisol (p < .05), and significantly improved aerobic fitness ( ; p < .001). With respect to cardiovascular and cardiac autonomic measures, rate pressure product (RPP) was significantly reduced at rest (p < .05) and during recovery after Stoop (p < .05), suggesting decreased myocardial oxygen consumption. In addition, baseline heart rate determined in the sitting position was significantly reduced (p < .05), while both baseline high frequency power (HF) determined in supine (p < .01) and cardiac baroreflex sensitivity (BRS) determined in the sitting position (p < .05) were increased after the FEM trial. In addition, BRS determined during mental challenge also marginally increased (p = .051). In summary, lifestyle intervention including HIIE training, Mediterranean-style eating plan, and a fish oil supplement significantly enhanced parasympathetic influence of the heart and improved fitness, blood profiles, and body composition.
| Identifer | oai:union.ndltd.org:ADTP/257779 |
| Date | January 2008 |
| Creators | Park, Young Jin, Medical Sciences, Faculty of Medicine, UNSW |
| Publisher | Publisher:University of New South Wales. Medical Sciences |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://unsworks.unsw.edu.au/copyright, http://unsworks.unsw.edu.au/copyright |
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