Identifier

etd-07102007-114010

Degree

Doctor of Philosophy (PhD)

Department

Kinesiology

Document Type

Dissertation

Abstract

This is a series of three experiments with brachial artery flow-mediated dilation (BAFMD) as the major outcome variable. The first study examined the temporal response of the brachial artery diameter following forearm occlusion in sixteen young (28±8 years) and fifteen older (85±8 years) men. Following release of the pressure cuff there is a significant reduction in brachial diameter compared to baseline, followed by a rapid increase to a PEAK. When comparing the magnitude of the decrease in diameter and the BAFMD between Young and Old, older subjects demonstrated a blunted response. A significant relation was noted between the magnitude of decrease and BAFMD (r=- 0.44, p= 0.04). Specific features of the biphasic pattern are blunted in older adults compared with younger subjects. The magnitude of the drop in diameter following forearm occlusion correlates with the magnitude of the BAFMD. The second study examined the relation between BAFMD and the total score from the Continuous Scale Physical Function Performance Test (PFP-10). Sixty-four men (84±11years) were studied. BAFMD was associated with the total PFP-10 score (r = 0.45, p = 0.0001) and age (r = -0.36, p = 0.003). When individuals were categorized based on their PFP-10 score, those in the highest functional class, exhibited the highest BAFMD, compared to those in the middle class, who had greater vasoreactivity than those in the lowest functional class. The final study examined the effects of four weeks of unilateral handgrip exercise training on BAFMD and the features of the vasoreactivity curve. Twelve men (81±5 years) were studied before, during and after four weeks of handgrip training of the non-dominant arm. Following training, a 40% increase in BAFMD was observed in the trained arm only. Significant improvements in BAFMD were observed after the second week of training (p=0.024). Also, BAFMD was significantly related to the estimated shear rate (r=0.341, p<0.001). A biphasic pattern was not observed in the present study. A significant improvement in BAFMD was observed following unilateral handgrip training. These improvements take place very rapidly and may be partly mediated through increases in shear stress resulting from changes in resistance vessel function.

Date

2007

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Michael Welsch

DOI

10.31390/gradschool_dissertations.3318

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