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Title: Two weeks of watermelon juice supplementation improves nitric oxide bioavailability but not endurance exercise performance in humans
Authors: Bailey, Stephen J.
Blackwell, Jamie R.
Williams, Ewan
Vanhatalo, Anni
Wylie, Lee J.
Winyard, Paul G.
Jones, Andrew M.
Keywords: Nitric oxide
Blood pressure
Muscle oxygenation
Issue Date: 2016
Publisher: © Elsevier
Citation: BAILEY, S.J. ...et al., 2016. Two weeks of watermelon juice supplementation improves nitric oxide bioavailability but not endurance exercise performance in humans. Nitric Oxide, 59, pp. 10-20.
Abstract: This study tested the hypothesis that watermelon juice supplementation would improve nitric oxide bioavailability and exercise performance. Eight healthy recreationally-active adult males reported to the laboratory on two occasions for initial testing without dietary supplementation (control condition). Thereafter, participants were randomly assigned, in a cross-over experimental design, to receive 16 days of supplementation with 300 mL·day-1 of a watermelon juice concentrate, which provided ~3.4g L-citrulline·day-1 and an apple juice concentrate as a placebo. Participants reported to the laboratory on days 14 and 16 of supplementation to assess the effects of the interventions on blood pressure, plasma [Lcitrulline], plasma [L-arginine], plasma [nitrite], muscle oxygenation and time-to-exhaustion during severe-intensity exercise. Compared to control and placebo, plasma [L-citrulline] (29 ± 4, 22 ± 6 and 101 ± 23 μM), [L-arginine] (74 ± 9, 67 ± 13 and 116 ± 9 μM) and [nitrite] (102 ± 29, 106 ± 21 and 201 ± 106 nM) were higher after watermelon juice supplementation (P<0.01). However, systolic blood pressure was higher in the watermelon juice (130 ± 11) and placebo (131 ± 9) conditions compared to the control condition (124 ± 8 mmHg; P<0.05). The skeletal muscle oxygenation index during moderate-intensity exercise was greater in the watermelon juice condition than the placebo and control conditions (P<0.05), but time-to-exhaustion during the severe-intensity exercise test (control: 478 ± 80, placebo: 539 ± 108, watermelon juice: 550 ± 143 s) was not significantly different between conditions (P<0.05). In conclusion, while watermelon juice supplementation increased baseline plasma [nitrite] and improved muscle oxygenation during moderate-intensity exercise, it increased resting blood pressure and did not improve time-to-exhaustion during severe-intensity exercise. These findings do not support the use of watermelon juice supplementation as a nutritional intervention to lower blood pressure or improve endurance exercise performance in healthy adults.
Description: This paper was accepted for publication in the journal Nitric Oxide and the definitive published version is available at http://dx.doi.org/10.1016/j.niox.2016.06.008.
Version: Accepted for publication
DOI: 10.1016/j.niox.2016.06.008
URI: https://dspace.lboro.ac.uk/2134/23174
Publisher Link: http://dx.doi.org/10.1016/j.niox.2016.06.008
ISSN: 1089-8603
Appears in Collections:Published Articles (Sport, Exercise and Health Sciences)

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