Time course of changes in endothelial function following exercise in habitually sedentary men

Regular exercise reduces mortality from cardiovascular dysfunction or disease. The mechanism(s) underlying this protective effect is unknown but may reflect enhanced nitric oxide activity. Two studies were conducted to investigate the effect of acute and chronic exercise on nitric oxide-mediated endothelium-dependent flow-mediated dilation (FMD) in habitually sedentary healthy male adults. Study A subjects (n=9, 30 plus or minus 4 yrs) conducted daily standardised treadmill exercise for 5 days. Brachial artery FMD was assessed daily and on the following 6 days. During the exercise period, FMD increased steadily, was elevated by Day 3 (P = 0.012) and reached maximal response on Day 6 (192 plus or minus 71 urn at day 6 versus 51 plus or minus 68 mu m at baseline, P = 0.002). FMD returned to baseline on Day 9. Study B subjects (n=17, 38 plus or minus 2 yrs) conducted a 4-week bike exercise regime. FMD was assessed pre-training, post-training and following 2-weeks detraining. Post-training FMD was improved (137 plus or minus 64 urn post-training versus 80 + 59 urn pre-training, P = 0.028) but returned to baseline following detraining (P = 0.226). In both studies, endothelium-independent responses remained similar throughout. Physical exercise progressively, rapidly and reversibly improves FMD. The effects are both rapid and short-lived.