1. George Rose and Thomas Owens
Acute dietary nitrate ingestion improves short duration supra-maximal exercise performance in trained cyclists
George Rose and Thomas Owens
School of Health, Sport and Professional Practice, University of South Wales, Pontypridd, United Kingdom.
Background
Results
Nitric oxide (NO), a signalling molecule and potent vasodilator linked to improved vascular function is derived from the catabolism of L-Arginine (1), and the reduction of nitrate (NO3-) and nitrite (NO2-) (2). The ingestion of dietary nitrate has been reported to improve exercise performance with a lower oxygen cost evident at submaximal work rates (3). Few studies have investigated the effect of dietary nitrate ingestion on short duration supra-maximal exercise performance. * *
Figure 3. Comparison of Peak power output for repeated sprints during nitrate () and placebo () supplemented conditions. *P < 0.05.
Peak power improved for all sprints under nitrate supplemented conditions, however only sprints one (a 3% improvement from 1144W to 1180W) and three (a 6% improvement from 872W to 933W) increased significantly (P < 0.05). Mean sprint power trended towards improved power outputs under nitrate supplemented conditions albeit without statistical significance.
Figure 1. Supramaximal repeated sprint protocol using Wingate cycle ergometer and online gas analysis.
Pre
Post
Figure 5. Systolic blood pressure pre and post repeated sprints for nitrate ( ̶̶̶ ̶̶ ̶ ) and placebo (---) conditions.
Figure 4. Mean V̇O2 for nitrate ( ̶̶̶ ̶ ̶ ) and placebo (---) conditions.
Table 1. Heart rate and blood pressure for nitrate and placebo test conditions measured immediately post exercise.
Placebo
Nitrate
Heart rate (b.min-1)
151 ± 10
148 ± 3
Systolic Blood Pressure (mmHg)
151 ± 9
143 ± 9
Diastolic Blood Pressure (mmHg)
78 ± 6
73 ± 7
Mean Arterial Pressure (mmHg)
102 ± 4
96 ± 6
Fatigue index (%)
29 ± 8
26 ± 8
Methods
Eight trained cyclists participated in a double-blind randomised cross-over study. A single 140 ml dose of concentrated beetroot juice (8 mmol NO3-) or placebo (concentrated blackcurrant juice) was ingested 2 hours prior to exercise. Participants completed five 10 s all out sprints interspersed with 30 s recovery, on a cycle ergometer (Monark, Ergomedic 894 E, Sweden). Peak and mean sprint power outputs, VO2 (Medical Graphics, Ultima CPX, UK), and heart rate (Polar, T31, Finland), were recorded for all sprints. Blood pressure was obtained using a manual sphygmomanometer (CardioKinetics, UK) 5 minutes prior to, and immediately post exercise. Following conformation of distribution normality (Shapiro-W-Wilk Tests), data were analysed using repeated-measures ANOVA. Wilcoxon signed rank order tests were used for post hoc analysis. Significance was established at P < 0.05 and data are expressed as mean ± SD.
Despite observed reductions in mean VO2, heart rate, blood pressure and fatigue index for nitrate supplementation conditions, results were statistically non-significant. The low sample size reported may have increased chances of making type II errors (not rejecting the null hypothesis).
Conclusions
These findings suggest a possible ergogenic effect of acute dietary nitrate ingestion on short duration supra-maximal repeated sprint exercise. Further research is required to confirm these findings and investigate potential mechanistic bases.
References
(1) Moncada and Higgs (1993) NEJM; 329,
(2) Larson et al. (2007) Acta Physiol; 191(1), 59-66
(3) Jones (2014) Sports Med 44, S35–45
Acknowledgements
The authors would like to acknowledge The Physiological Society for a travel grant to attend this meeting.
Figure 2. Double-blind randomised cross-over study design.