Peripheral arterial disease (PAD) results in a failure to adequately supply blood and oxygen (O(2)) to working tissues and presents as claudication pain during walking. Nitric oxide (NO) bioavailability is essential for vascular health and function. Plasma nitrite (NO(2)(-)) is a marker of vascular NO production but may also be a protected circulating "source" that can be converted to NO during hypoxic conditions, possibly aiding perfusion. We hypothesized that dietary supplementation of inorganic nitrate in the form of beetroot (BR) juice would increase plasma NO(2)(-) concentration, increase exercise tolerance, and decrease gastrocnemius fractional O(2) extraction, compared with placebo (PL). This was a randomized, open-label, crossover study. At each visit, subjects (n = 8) underwent resting blood draws, followed by consumption of 500 ml BR or PL and subsequent blood draws prior to, during, and following a maximal cardiopulmonary exercise (CPX) test. Gastrocnemius oxygenation during the CPX was measured by near-infrared spectroscopy. There were no changes from rest for [NO(2)(-)] (152 ± 72 nM) following PL. BR increased plasma [NO(2)(-)] after 3 h (943 ± 826 nM; P ≤ 0.01). Subjects walked 18% longer before the onset of claudication pain (183 ± 84 s vs. 215 ± 99 s; P ≤ 0.01) and had a 17% longer peak walking time (467 ± 223 s vs. 533 ± 233 s; P ≤ 0.05) following BR vs. PL. Gastrocnemius tissue fractional O(2) extraction was lower during exercise following BR (7.3 ± 6.2 vs. 10.4 ± 6.1 arbitrary units; P ≤ 0.01). Diastolic blood pressure was lower in the BR group at rest and during CPX testing (P ≤ 0.05). These findings support the hypothesis that NO(2)(-)-related NO signaling increases peripheral tissue oxygenation in areas of hypoxia and increases exercise tolerance in PAD.

Although exercise improves individual risk factors for metabolic syndrome (MS), there is little research on the effect of exercise on MS as a whole. The objective of this study was to determine how much exercise is recommended to decrease the prevalence of MS. Of 334 subjects randomly assigned, 227 finished and 171 (80 women, 91 men) had complete data for all 5 Adult Treatment Panel III-defined MS risk factors and were included in this analysis. Subjects were randomly assigned to a 6-month control or 1 of 3 eight-month exercise training groups of (1) low amount/moderate intensity (equivalent to walking approximately 19 km/week), (2) low amount/vigorous intensity (equivalent to jogging approximately 19 km/week), or (3) high amount/vigorous intensity (equivalent to jogging approximately 32 km/week). The low-amount/moderate-intensity exercise prescription improved MS relative to inactive controls (p <0.05). However, the same amount of exercise at vigorous intensity was not significantly better than inactive controls, suggesting that lower-intensity exercise may be more effective in improving MS. The high-amount/vigorous-intensity group improved MS relative to controls (p <0.0001), the low-amount/vigorous-intensity group (p = 0.001), and the moderate-intensity group (p = 0.07), suggesting an exercise-dose effect. In conclusion, a modest amount of moderate-intensity exercise in the absence of dietary changes significantly improved MS and thus supported the recommendation that adults get 30 minutes of moderate-intensity exercise every day. A higher amount of vigorous exercise had greater and more widespread benefits. Finally, there was an indication that moderate-intensity may be better than vigorous-intensity exercise for improving MS.

In nondieting, overweight subjects, the controls gained weight, both low-amount exercise groups lost weight and fat, and the high-amount group lost more of each in a dose-response manner. These findings strongly suggest that, absent changes in diet, a higher amount of activity is necessary for weight maintenance and that the positive caloric imbalance observed in the overweight controls is small and can be reversed by a modest amount of exercise. Most individuals can accomplish this by walking 30 minutes every day.