The Acute Effects of Exercise on Endothelial Function

Abstract

The function of the brachial artery is correlated to the function of the coronary arteries. Therefore, it is important to understand the transient changes in endothelial function of the brachial artery after exercise. Previous studies investigating the effect of acute exercise on endothelial function provide a mixture of conflicting results, much of which may stem from the various methodologies used to present the data. PURPOSE: The purpose of this study was two-fold: 1) to compare brachial artery endothelial function at rest and post-exercise in young, healthy subjects, and 2) to compare the data expressed as a percent change and normalized to shear rate area under the curve (SRAUC) to determine if normalizing the data to SRAUC nullifies the changes in endothelial function from rest to post-exercise. METHODS: Fifteen young, healthy subjects completed blood vessel function tests at rest and immediately after a 30-minute treadmill exercise session at 60% velocity at VO2max. Wall tracking of high-resolution ultrasound images of the brachial artery were analyzed during endothelium-dependent flow-mediated dilation (FMD) and endothelium-independent, nitroglycerin-mediated dilation. Results of FMD were calculated as percent change in diameter and also normalized for SRAUC. RESULTS: Post-exercise, FMD (presented as percent change) was reduced compared to the rest condition (8.89% ± 4.29 to 5.83% ± 3.88, p <.05), but normalizing for SRAUC nullified this difference (3.57×10-4% ± 1.76×10-4 to 2.69×10-4% ± 2.42×10-4, p =.25). Baseline SR was significantly greater after exercise than at rest (223.57 s-1 ± 72 to 353.54 s-1 ± 158.17, p <.05). Baseline diameter, time to peak diameter, SRAUC, and endothelium-independent vasodilation were not significantly different between the two conditions. The relationship between SRAUC and FMD was strong at rest (r =.82, p <.001), but weak post-exercise (r =.16, p =.6). CONCLUSION: When expressed as a percent change from baseline, FMD is blunted post-exercise. However, when the data is normalized for SRAUC there are no differences in FMD pre- and post-exercise. Due to the lack of relationship in FMD and SRAUC after exercise, these data suggest that it may not be appropriate to normalize FMD data following acute exercise.