Age and Sex Differences in Local Vasodilation and Exercise Hyperemia
Open Access
- Author:
- Parker, Beth A.
- Graduate Program:
- Kinesiology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- January 24, 2008
- Committee Members:
- David Nathan Proctor, Committee Chair/Co-Chair
William Lawrence Kenney Jr., Committee Member
Donna Hope Korzick, Committee Member
James Anthony Pawelczyk, Committee Member
Steven Howard Zarit, Committee Member - Keywords:
- femoral artery
leg blood flow
sex differences
aging
leg vascular conductance
flow-mediated dilation - Abstract:
- Local alterations in vasodilator responsiveness may significantly influence the leg hyperemic response to dynamic exercise in aging humans in a sex-specific manner. This series of dissertation studies was designed to examine local alterations in leg vasodilatory responsiveness with age in women, directly test the hypothesis that older women would exhibit greater reductions in leg exercise hyperemia than men during exercise not limited by central mechanisms, and examine the consequences for observed alterations in leg vasodilation during exercise in older women. The purpose of the first study was to compare age differences in brachial and popliteal flow-mediated dilation (FMD) and shear rate in women. Findings suggest that FMD is lower with age in women in both limbs, perhaps due to reductions in smooth muscle responsiveness. The purpose of the second study was to test the hypothesis that metabolic inhibition of a sympathetic stimulus (i.e., sympatholysis) is reduced with age in the lower extremity vasculature of women. Findings suggest that older women exhibit diminished popliteal artery reactivity and reduced sympatholysis in the leg resistance vasculature. The purpose of the third study was to test hypothesis that exercise-induced vasodilator responses are greater in young women than men. Findings suggest that the vasodilatory response to dynamic leg exercise is greater in young women vs. men. The purpose of the fourth study was to test the hypothesis that age by sex interactions in exercising leg hemodynamics persist during small muscle mass exercise that is not limited by cardiac output. Findings suggest that local (non-cardiac) factors underlie the blunted leg vasodilation observed in older women but not older men. The purpose of the fifth study was to test the hypothesis that active muscle oxygen extraction would be higher in older women during knee extensor exercise. Findings suggest that older women do not compensate for blunted whole limb hyperemia through an augmentation of local oxygen extraction. These studies provide evidence for alterations in local vasodilator control and blunted leg vasodilation during exercise in older women, which may affect exercise capacity and blood pressure regulation.