Vascular reactivity at rest and during exercise in middle-aged obese men: effects of short-term, low-intensity, exercise training
Résumé
Objective: Although increased blood flow (BF) in exercising muscles is thought to be impaired in obese subjects and may contribute to physical inactivity, data are scarce in this regard and the involvement of endothelium dysfunction remains partly hypothetical. Methods: A total of 16 middle-aged obese men (body mass index, BMIX30 kg m À2) and 16 normal-weight men (BMIo25 kg m À2), matched for age, were recruited. We used ultrasonography to compare intima-media thickness (IMT) and distensibility of the carotid artery, flow-mediated dilation (FMD), nitrate-dependent dilation (NDD) and peak BF during post-ischemic hyperemia in the brachial artery (a conduit artery), and leg BF during knee-extensor exercise (indicative of resistance vessel function) in obese and in normal-weight men. In addition, 10 obese men participated in an 8 week individualized low-intensity training program. Results: Compared with normal-weight men, obese men had higher carotid IMT (0.50 ± 0.01 vs 0.62 ± 0.04 mm, Po0.05) but lower carotid distensibility (0.26±0.03 vs 0.11±0.03 mm Hg À1 10 À2 , Po0.05), FMD (5.7±0.4 vs 3.3±0.5%, Po0.05) and peak BF during post-ischemic hyperemia (398 ± 52 vs 229 ± 24%, Po0.05), despite similar maximal shear rate, without NDD differences. Lower limb BF (ml min À1 100 g À1) increased significantly from rest to maximal exercise in both groups with lower values in obese men (at peak power, 36.9 ± 1.6 vs 31.5 þ 2.2 ml min À1 100 g À1 , Po0.05). Exercise training normalized carotid distensibility (0.14±0.04 before vs 0.23±0.03 mm Hg À1 10 À2 after training, P ¼ 0.09) and FMD (2.7±0.4 before vs 4.8±0.5% after training, Po0.05), but did not improve brachial post-ischemic peak BF or exercising leg BF. Conclusions: In obese men, conduit and resistance vessel reactivity is depressed, but a short-term low-intensity exercise training improves distensibility and endothelium dependent vasodilation in the large conduit artery, but not post ischemic or exercise muscle BF.