Abstract
Endothelial dysfunction is observed with aging but is offset by high fitness. Changes in endothelial function (flow-mediated dilation, FMD) with episodic exercise may lead to sustained improvements in vascular function. The effect of exercise intensity and fitness on the acute FMD response in the elderly is unknown. Our aim was to assess the effect of exercise intensity on FMD in low- and high-fit elderly. 47 men (70±5 yrs) were stratified into low- and high-fit groups based on their cardiorespiratory fitness (VO2peak 24±3 vs. 36±5 ml.kg-1.min-1). Participants cycled at a moderate-intensity (40% peak power output, PPO), a high-intensity (intervals at 70% PPO) or seated-rest (control), in a randomised order. Brachial FMD was assessed at rest, 10 and 60 min post. In control, FMD decreased by 0.74 % (95% CI, -1.34 to -0.03, P=0.05) at 60 min in both groups. FMD increased 10 min after moderate-intensity exercise in both groups [mean increase of 0.86 % (95% CI, 0.17 to 1.56), P=0.01], but returned to baseline at 60 min. In the low-fit, FMD was reduced 10 and 60 min after high-intensity exercise [reduction of ~0.80 %, P<0.05). After high-intensity exercise in the high-fit, FMD was unchanged at 10 min, but increased after 60 min [mean difference of 1.52 % (95% CI, 0.41 to 2.62), P<0.001]. Reductions in FMD with sitting can be offset with moderate-intensity exercise in low- and high-fit elderly. Fitness modulates the FMD response to different exercise intensity. Sustained impairment of FMD in low-fit after high-intensity exercise may represent a signal for vascular adaptation and/or a period of increased cardiovascular risk following exercise.