Doctor of Philosophy (PhD)
This is a series of 3 experiments in the area of vasoreactivity. The first study investigated the stability and reproducibility of brachial artery flow-mediated dilation (BAFMD). Twenty-six healthy volunteers underwent 3 scans on 2 days, performed by 2 ultrasonographers, and analyzed by 2 readers. All subjects were tested between 7 and 11am after refraining from food and exercise. Average baseline diameter was 3.48±0.53mm, which increased to 3.71±0.57mm (6.58±4.15%) at peak dilation. ICCC's for days, testers and readers were 0.9188, 0.9394, and 0.8982 respectively. To detect a difference in vasoreactivity of 60% (two-tailed), e.g. 5% vasodilation versus 8% vasodilation, at 90% power, 23 and 10 subjects would be required for cross-sectional and pre-post designs, respectively. These data indicate adequate stability and reproducibility of the BAFMD technique under controlled conditions. The second study investigated the relation between BAFMD and normal plasma fibrinogen (PF) in 30 non-smoking, healthy, volunteers (41±12 yr.; range:22-57). Results indicated a 6.08% increase (range:-3.58 to 17.48%) in BAFMD. Correlation analysis indicated significant inverse relationships for BAFMD and age r=-0.417 (p=0.02), and for BAFMD and PF r=-0.56 (p=0.001). Stepwise multiple regression including PF, age, total cholesterol and blood pressure revealed PF as the predominant predictor for BAFMD with 31% of the variance accounted for by BAFMD =22.61-(0.05836*PF), with no other variables entered. The final study examined the time-course of changes in BAFMD in response to a localized exercise training protocol. Fourteen healthy males (age: 26±5.7) underwent BAFMD assessment prior to, during and following 4 weeks (5 days per week) of 60% maximal voluntary contraction handgrip training of the non-dominant arm. Following training, paired t-tests revealed a 62% increase in BAFMD for the trained arm (6.2±3.0% to 10±4.1%), compared to baseline (p=0.0004), and a 100% difference (10±4.1% vs. 4.6±4.4%) between arms (p=0.0001). An increase in BAFMD (6.2±3.0% to 8.25±2.4%), was evident following 4 days of training (p=0.015), although individual participant variability reduced the statistical power of these findings. There were no changes in hemodynamic, autonomic and hematological variables, suggesting the improvement was a locally mediated process.
Document Availability at the Time of Submission
Release the entire work immediately for access worldwide.
Allen, Jason David, "The time-course of vascular adaptations following localized short term exercise training" (2001). LSU Doctoral Dissertations. 3455.