Influence of acute dietary nitrate supplementation on 50 mile time trial performance in well-trained cyclists

Abstract

Dietary nitrate supplementation has been reported to improve short distance time trial (TT) performance by 1-3 % in club-level cyclists. It is not known if these ergogenic effects persist in longer endurance events or if dietary nitrate supplementation can enhance performance to the same extent in better trained individuals. Eight well-trained male cyclists performed two laboratory-based 50 mile TTs: (1) 2.5 h after consuming 0.5 L of nitrate-rich beetroot juice (BR) and (2) 2.5 h after consuming 0.5 L of nitrate-depleted BR as a placebo (PL). BR significantly elevated plasma [NO(2) (-)] (BR: 472 ± 96 vs. PL: 379 ± 94 nM; P < 0.05) and reduced completion time for the 50 mile TT by 0.8 % (BR: 136.7 ± 5.6 vs. PL: 137.9 ± 6.4 min), which was not statistically significant (P > 0.05). There was a significant correlation between the increased post-beverage plasma [NO(2) (-)] with BR and the reduction in TT completion time (r = -0.83, P = 0.01). Power output (PO) was not different between the conditions at any point (P > 0.05) but oxygen uptake ([Formula: see text]O(2)) tended to be lower in BR (P = 0.06), resulting in a significantly greater PO/[Formula: see text]O(2) ratio (BR: 67.4 ± 5.5 vs. PL: 65.3 ± 4.8 W L min(-1); P < 0.05). In conclusion, acute dietary supplementation with beetroot juice did not significantly improve 50 mile TT performance in well-trained cyclists. It is possible that the better training status of the cyclists in this study might reduce the physiological and performance response to NO(3) (-) supplementation compared with the moderately trained cyclists tested in earlier studies.

Dietary nitrate supplementation enhances high-intensity running performance in moderate normobaric hypoxia, independent of aerobic fitness

“…Peak plasma nitrite concentration was 602 % higher in BRJ versus PLA, similar to Arnold et al [38] (775 %) (~ 7 mmol nitrate), but considerably greater than reported by Muggeridge et al [22] (134 %) (~ 5 mmol nitrate) and Vanhatalo et al [8] (150 %) (~ 9.3 mmol). Importantly, all participants increased plasma nitrite concentration by substantially greater than 30 % -a cut off proposed by Wilkerson [20] for identifying 'non-responders'. This may, in part, be a consequence of the high nitrate dose administered, and may help explain the consistent ergogenic effect observed in this study.…”

“…Conversely, studies in well-trained individuals exercising in hypoxia have typically found no effect of nitrate supplementation [38][39][40]. Well-trained individuals exhibit increased presence and activity of the NOS enzymes [31]; possess higher baseline nitrate/nitrite concentration [29]; may habitually consume high levels of nitrate as a consequence of their large daily energy intake [30]; and experience lower tissue acidosis and hypoxia [20] relative to the untrained. Moreover, a recent investigation in normoxia observed an inverse correlation between aerobic fitness and the response to nitrate supplementation [17].…”

“…Conversely, well-trained participants (V O2max > 60 ml·kg -1 ·min -1 ) are typically less responsive to dietary nitrate supplementation [17,[19][20][21][25][26][27], even when very high nitrate doses (~ 19.5 mmol) are administered [28]. Highly-trained individuals are known to possess elevated baseline nitrate/ nitrite reserves [29], may habitually consume large amounts of nitrate, subsequent to their increased calorie consumption [30], and exhibit greater presence and activity of the NOS enzymes, relative to the untrained [31].…”

Nitrate pharmacokinetics: Taking note of the difference

“…There is no observable trend to indicate higher baseline plasma levels influence the peak yield, but this remains to be tested directly. Figure 3 shows the scatter between measured plasma [NO The influence of NO 3 -supplementation on a wide range of exercise activities has been investigated, ranging from 500 m kayaking [24] to 50 miles cycling [25], with predictably mixed results. While the majority of studies to date have assessed the influence of NO 3 -supplementation on continuous exercise, a few have considered possible effects on intermittent high-intensity exercise tests which are reflective of the pattern of exertion during team sports.…”

Acute whole body UVA irradiation combined with nitrate ingestion enhances time trial performance in trained cyclists

“…Conversely, several other studies report exercise performance of varying modalities to be unaltered by dietary nitrate supplementation (Peacock et al, 2012, Wilkerson et al, 2012, Muggeridge et al, 2013. While there are various methodological differences between studies that may account for this disparity, it has become apparent that ergogenic effects appear minimal in highly-trained endurance cohorts (Peacock et al, 2012, Christensen et al, 2013.…”