Abstract
Endothelial dysfunction measured via flow-mediated dilation (FMD) is an early marker of atherogenesis, and is associated with increased cardiovascular disease risk. Aerobic exercise training improves FMD in mostly Caucasian (C) populations, but has not been assessed in African Americans (AA). PURPOSE: To evaluate the effect of aerobic exercise training on FMD in sedentary AA and C postmenopausal women. METHODS: Eight healthy, but sedentary AA (age= 55.8 + 1.7 yr, VO2 peak= 21.0 + 3.9 ml/kg/min) and 16 C (age= 57.2 + 5.9 yr, VO2 peak= 21.8 + 3.7 ml/kg/min) postmenopausal women participated in 12 weeks of aerobic exercise training four times per week (two days below the lactate threshold (RPE=10-12), and two days above the lactate threshold (RPE=15-17) to a designated caloric expenditure per session (250, 300, or 350 kcals). VO2 peak was assessed before and after training with an incremental exercise test on a motor-driven treadmill. Endothelial function was evaluated at pre-intervention and post-intervention via FMD, which was quantified by comparing B-mode ultrasound images of the brachial artery at rest and during reactive hyperemia after 5 minutes of forearm occlusion. RESULTS: Despite a significant improvement in VO2 peak (AA=13.5% vs. C=18.3%), exercise training did not significantly improve FMD in AA (5.77% to 5.68%, p= 0.950) or C subjects (5.68% to 6.64%, p=0.267). However, there was a significant improvement in FMD in subjects who had endothelial dysfunction (2.22% to 6.16%, p=0.007) at baseline, but not in subjects with normal endothelial function (7.76% to 6.67%, p= 0.508). CONCLUSION: In the present study, we observed no significant improvement in FMD in AA or C subjects. However, we found that exercise training improves FMD in subjects with endothelial dysfunction, but does not further increase FMD in postmenopausal women with previously normal or high endothelial function. Supported by NIH grant RR00847 to the GCRC
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