Isometric exercise training has been shown to bring about beneficial reductions in resting blood pressure, however the physiological mechanism responsible remain equivocal. It is currently unknown whether isometric exercise training-induced reductions in resting blood pressure are associated with improvements in vascular endothelial function and structure. The aim of this thesis was to investigate the effect of an 8-week isometric exercise training intervention on resting blood pressure, conduit artery vascular endothelial function, artery diameter and blood flow patterns at rest. Fourteen healthy young males (mean age: 23 ± 4 years; body mass: 80.7 ± 11.0kg; height: 178.8 ± 6.2cm) completed 8-weeks of isometric bilateral leg extension exercise training at high intensity (105.4% 2-min torquepeak). Three exercise sessions were performed each week and each session consisted of four 2-minute isometric muscular contractions each separated by a 3-minute recovery period. Resting blood pressure was measured using brachial artery oscillometric methods at pre, mid and post intervention. Brachial artery flow-mediated vasodilatation and resting artery diameter and blood flow were assessed at pre, week 2, mid, week 6 and post intervention using high-resolution duplex Doppler ultrasound. Total peripheral resistance and cardiac output were determined at pre and post intervention using high-resolution echocardiography. A generalised estimating equation analysis was used to estimate the effect of exercise versus non-exercise intervention over time on resting blood pressure, brachial artery flow-mediated vasodilatation, artery diameter and blood flow, total peripheral resistance and cardiac output. Isometric bilateral leg extension exercise training reduced resting systolic blood pressure (training: 117 vs. control: 121 mmHg) (P=0.002) and resting mean arterial pressure (training: 88 vs. control: 91 mmHg) (P=0.001) following 4 weeks of exercise training compared to the control condition. Brachial artery flowmediated vasodilatation was increased (mid training: 8.65 ± 1.02% vs. mid control: 6.38 ± 1.14%) (P=0.011). Superficial femoral artery diameter, antegrade blood flow and antegrade shear rate were increased (all P≤0.05), whilst superficial femoral retrograde shear rate was decreased (P=0.013) following 2 weeks of exercise training compared to the control condition. There were no significant condition by time interactions observed in resting blood pressure, vascular endothelial function, artery diameter or blood flow patterns following 8 weeks of exercise training (all P≥0.05). Cardiac output was not significantly different following 8 weeks of exercise training (P=0.148). Total peripheral resistance was increased following 8 weeks of exercise training compared to the non-exercising control condition (P=0.054). Isometric bilateral leg extension exercise training can effectively lower resting blood pressure and increase conduit artery endothelium-dependent vasodilatation in healthy young men after 4 weeks with a concomitant reduction in resting blood pressure. These beneficial adaptations were no longer evident from mid to post exercise training in healthy normotensive young men.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:723550 |
| Date | January 2016 |
| Creators | Howland, Lucinda Jayne |
| Publisher | Canterbury Christ Church University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://create.canterbury.ac.uk/16256/ |
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