In:
Journal of Applied Physiology, American Physiological Society, Vol. 110, No. 3 ( 2011-03), p. 591-600
Abstract:
Dietary supplementation with beetroot juice (BR) has been shown to reduce resting blood pressure and the O 2 cost of submaximal exercise and to increase tolerance to high-intensity cycling. We tested the hypothesis that the physiological effects of BR were consequent to its high NO 3 − content per se, and not the presence of other potentially bioactive compounds. We investigated changes in blood pressure, mitochondrial oxidative capacity (Q max ), and physiological responses to walking and moderate- and severe-intensity running following dietary supplementation with BR and NO 3 − -depleted BR [placebo (PL)]. After control (nonsupplemented) tests, nine healthy, physically active male subjects were assigned in a randomized, double-blind, crossover design to receive BR (0.5 l/day, containing ∼6.2 mmol of NO 3 − ) and PL (0.5 l/day, containing ∼0.003 mmol of NO 3 − ) for 6 days. Subjects completed treadmill exercise tests on days 4 and 5 and knee-extension exercise tests for estimation of Q max (using 31 P-magnetic resonance spectroscopy) on day 6 of the supplementation periods. Relative to PL, BR elevated plasma NO 2 − concentration (183 ± 119 vs. 373 ± 211 nM, P 〈 0.05) and reduced systolic blood pressure (129 ± 9 vs. 124 ± 10 mmHg, P 〈 0.01). Q max was not different between PL and BR (0.93 ± 0.05 and 1.05 ± 0.22 mM/s, respectively). The O 2 cost of walking (0.87 ± 0.12 and 0.70 ± 0.10 l/min in PL and BR, respectively, P 〈 0.01), moderate-intensity running (2.26 ± 0.27 and 2.10 ± 0.28 l/min in PL and BR, respectively, P 〈 0.01), and severe-intensity running (end-exercise O 2 uptake = 3.77 ± 0.57 and 3.50 ± 0.62 l/min in PL and BL, respectively, P 〈 0.01) was reduced by BR, and time to exhaustion during severe-intensity running was increased by 15% (7.6 ± 1.5 and 8.7 ± 1.8 min in PL and BR, respectively, P 〈 0.01). In contrast, relative to control, PL supplementation did not alter plasma NO 2 − concentration, blood pressure, or the physiological responses to exercise. These results indicate that the positive effects of 6 days of BR supplementation on the physiological responses to exercise can be ascribed to the high NO 3 − content per se.
Type of Medium:
Online Resource
ISSN:
8750-7587
,
1522-1601
DOI:
10.1152/japplphysiol.01070.2010
Language:
English
Publisher:
American Physiological Society
Publication Date:
2011
detail.hit.zdb_id:
1404365-8
SSG:
12
SSG:
31
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