| Endothelial dysfunction is an important early marker of increased risk of atherosclerosis and cardiovascular disease and has increased prevalence in obesity. Exercise has been suggested as an intervention for improving endothelial function. Purpose. To examine the effects of exercise intensity on acute changes in endothelial function in lean and obese adults. Methods. Sixteen lean (BMI 30, age 26 +/- 6yr) adults completed a cycle ergometry lactate threshold (LT)NO2peak test. Subjects were studied during 3 randomized admissions [control (C, no exercise), moderate (M, LT) and high (H, > LT) intensity cycle ergometer exercise (30 min)]. Flow-mediated dilation (FMD) was assessed by Doppler ultrasound at baseline and at 1, 2, and 4 h post-exercise. Results. RM ANCOVA revealed significant main effects for group (p = 0.005), time (p = 0.022), and group x condition interaction (p = 0.036). Post-hoc analyses indicated that lean subjects exhibited greater increases in FMD than obese subjects (p = 0.0005). FMD did not increase significantly over time in any condition in the obese group, but a trend was observed for increases at 2- and 4-hr after M (p = 0.08 for both). For lean subjects, FMD increased at 2- and 4-hr after C and M, and at all time points after H. FMD responses of lean and obese subjects significantly differed after C and H, but not after M. The increase in FMD after H in lean subjects (3.2 +/- 0.5%) was significantly greater than after both C (1.7 +/- 0.4%, p = 0.015) and M (1.4 +/- 0.4%, p = 0.002). FMD values after M were not significantly greater than after C in lean subjects. FMD responses were not significantly related to waist circumference, % body fat, or VO2peak. Conclusion. In lean young adults, high-intensity exercise acutely enhances endothelial function for at least 4 hrs, while moderate-intensity exercise of the same duration has no significant effect. In contrast, obese subjects are resistant to the salutary effect of acute exercise on FMD. |
