Effect of Dietary Nitrate Supplementation on Swimming Performance in Trained Swimmers

Abstract

Nitrate supplementation appears to be most ergogenic when oxygen availability is restricted and subsequently may be particularly beneficial for swimming performance due to the breathhold element of this sport. This represents the first investigation of nitrate supplementation and swimming time-trial (TT) performance.In a randomised double-blind repeated-measures crossover study, ten (5male, 5female) 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 x 21m lengths) backstroke.Pre-exercise fractional exhaled nitric oxide concentration was significantly elevated with nitrate compared to placebo (17±9 vs. 7±3p.p.b., p=0.008). 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=0.144; 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=0.678; 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=0.062; 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>0.30).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.3

Effect of beetroot juice supplementation on 10-km performance in recreational runners

“…The variation at the final time of the 10-km running performance test between the BRJ and PLA conditions was 0.9 ± 2.1 minutes (P = 0.130), indicating an improvement of 1.9 ± 4.2% on running performance with a "trivial" effect size. Our results are in agreement with D r a f t previous studies that evaluated the effects of BRJ on long duration endurance performance (Shannon et al, 2017;Wilkerson et al, 2012) and with a literature review and meta-analysis that found a "trivial" but not significant effect in favor of dietary supplementation of NO 3 -, which can be translated into improvement of 0.8% in the final performance (McMahon et al, 2016). Although the result of the present study may seem small in the competitive environment in which athletes have very similar levels of performances, the improvement of 0.5 to 1.5% is considered sufficient to make a difference between the competitors (Dominguéz et al, 2018;Paton and Hopkins, 2006) as well as the final result of the performance.…”

“…Boorsma et al (2014) did not find improvement in the completion time of 1500 m after the acute or chronic BRJ supplementation in trained runners despite the fact that two individuals were identified as high responders. On the contrary, in another study using the same distance and a similar sample, acute supplementation with BRJ was able to reduce the test time in supplemented individuals (Shannon et al 2017). At longer distances (5-km), with moderately trained individuals, acute supplementation with 500 mg NO 3 -, despite having a tendency to increase the mean final velocity of the test and a statistically significant increase of 5 % of velocity in the last third of the test with reduction of RPE in the supplemented group, did not find statistical differences in the time of conclusion of the test (Murphy et al, 2012).…”

“…Most of the studies reporting positive effects of acute or chronic NO 3 supplementation on time trial performances included tests with a duration of less than 30 minutes of moderate or high intensity (Peeling et al, 2014;Cermak et al, 2012a;Lansley et al, 2011a) when compared with longer duration exercise (Shannon et al, 2017;Cermak et al, 2012b;Wilkerson et al, 2012). It was shown that a single dose of BRJ was not able to D r a f t improve the 10-km time trial performance in trained runners (Shannon et al, 2017) as well as in the 50-mile test performance (Wilkerson et al, 2012) or even in the 1-hour time trial performance in well-trained cyclists (Cermak et al, 2012b).…”

“…In addition to the duration and intensity of the exercise, it is speculated that the level of training of athletes influences the effects of supplementation with NO 3 - (Campos et al, 2018;Carriker et al, 2016;Porcelli et al, 2015). Although there is no agreement (Campos et al, 2018;McMahon et al, 2016;Hoon et al, 2014), it is believed that the effects of BRJ supplementation are less expressive in well-trained athletes when compared to active or moderately trained individuals (Shannon et al, 2017;Boorsma et al, 2014;Wilkerson et al, 2012;Cermak et al, 2012b), although there are athletes classified as "responders" (Jonvik et al, 2015).…”

The benefits and risks of beetroot juice consumption: a systematic review

“…Furthermore in healthy trained male and female apnoeists, one single shot of BRJ did not show physiological improvements in heart rate for VO 2 that indicate a beneficial effect of BRJ for free divers (Barlow et al 2018). Also, no beneficial effects on short distance swimming performance and under water phases in a time trial were found in a study performed in well trained swimmers (Lowings et al 2017). Effects of the consumption of a single dose of nitrate-rich BRJ on muscular function or training adaptations here seem beneficial; however, this is not applicable for apnoeists and swimmers.…”