Effect of Dietary Nitrate Supplementation on Swimming Performance in Trained Swimmers

• Autores: Sam Lowings, Oliver Michael Shannon, Kevin Deighton, Jamie Matu, Matthew John Barlow
• Localización: International journal of sport nutrition and exercise metabolism, ISSN 1526-484X, ISSN-e 1543-2742, Vol. 27, Nº. 4, 2017, págs. 377-384
• Idioma: inglés
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• Resumen

  • Nitrate supplementation appears to be most ergogenic when oxygen availability is restricted and subsequently may be particularly beneficial for swimming performance due to the breath-hold element of this sport. This represents the first investigation of nitrate supplementation and swimming time-trial (TT) performance. In a randomized double-blind repeated-measures crossover study, ten (5 male, 5 female) trained swimmers ingested 140ml nitrate-rich (~12.5mmol nitrate) or nitrate-depleted (~0.01mmol nitrate) beetroot juice. Three hours later, subjects completed a maximal effort swim TT comprising 168m (8 × 21m lengths) backstroke. Preexercise fractional exhaled nitric oxide concentration was significantly elevated with nitrate compared with placebo, Mean (SD): 17 (9) vs. 7 (3)p.p.b., p = .008. Nitrate supplementation had a likely trivial effect on overall swim TT performance (mean difference 1.22s; 90% CI -0.18–2.6s; 0.93%; p = .144; d = 0.13; unlikely beneficial (22.6%), likely trivial (77.2%), most unlikely negative (0.2%)). The effects of nitrate supplementation during the first half of the TT were trivial (mean difference 0.29s; 90% CI -0.94–1.5s; 0.46%; p = .678; d = 0.05), but there was a possible beneficial effect of nitrate supplementation during the second half of the TT (mean difference 0.93s; 90% CI 0.13–1.70s; 1.36%; p = .062; d = 0.24; possibly beneficial (63.5%), possibly trivial (36.3%), most unlikely negative (0.2%)). The duration and speed of underwater swimming within the performance did not differ between nitrate and placebo (both p > .30). Nitrate supplementation increased nitric oxide bioavailability but did not benefit short-distance swimming performance or the underwater phases of the TT. Further investigation into the effects of nitrate supplementation during the second half of performance tests may be warranted.