Another good reason to keep up with exercise: "Age is the major risk factor for cardiovascular diseases (CVD) and this is attributable in part to stiffening of large elastic arteries and development of vascular endothelial dysfunction (e.g., impaired endothelium-dependent dilation, EDD). In contrast, regular aerobic exercise is associated with reduced risk of CVD. Endurance exercise-trained middle-aged/older adults demonstrate lower large elastic artery stiffness and greater EDD than their sedentary peers. With daily brisk walking, previously sedentary middle-aged/older adults show reduced stiffness and improved EDD. The mechanisms underlying the effects of regular aerobic exercise on large elastic artery stiffness with aging are largely unknown, but likely include changes to the composition of the arterial wall. Enhanced EDD in older adults who exercise is mediated by increased nitric oxide (NO) bioavailability associated with reduced oxidative stress. Arteries from old rodents that undergo aerobic exercise training demonstrate increased expression and activity of endothelial NO synthase, reduced oxidative damage associated with reduced expression and activity of the oxidant enzyme NADPH oxidase, and increased activity of the antioxidant enzyme superoxide dismutase. Aerobic exercise also may protect arteries with aging by increasing resistance to the effects of other CVD risk factors like LDL-cholesterol. Habitual aerobic exercise is an effective strategy to combat arterial aging."