Nitrate supplementation and high-intensity performance in competitive cyclists

Abstract

Consumption of inorganic nitrate (NO3(-)) is known to enhance endurance exercise performance in recreationally trained subjects. Here we report the effect on a high-intensity performance task in national-level cyclists. The performance test consisted of 2 cycle ergometer time trials of 4 min duration with 75 min between trials. In a randomized crossover design, 26 cyclists performed the test under the following 4 conditions (each separated by a 6-day washout): consumption of 70 mL of nitrate-rich beetroot juice at 150 min or 75 min before the first time trial, addition of a 35 mL "top-up dose" following the first time trial in the 150 min condition, and consumption of a placebo. A linear mixed model with adjustments for learning effects and athlete fitness (peak incremental power) was used to estimate effects on mean power, with probabilistic inferences based on a smallest important effect of 1.0%. Peak plasma nitrite (NO2(-)) concentration was greatest when nitrate was taken 75 min before the first time trial. Relative to placebo, the mean effect of all 3 nitrate treatments was unclear in the first time trial (1.3%, 90% confidence limits: ±1.7%), but possibly harmful in the second time trial (-0.3%, ±1.6%). Differences between nitrate treatments were unclear, as was the estimate of any consistent individual response to the treatments. Allowing for sampling uncertainty, the effect of nitrate on performance was less than previous studies. Under the conditions of our experiment, nitrate supplementation may be ineffective in facilitating high-intensity exercise in competitive athletes.

Single and Combined Effects of Beetroot Crystals and Sodium Bicarbonate on 4-km Cycling Time Trial Performance

“…Furthermore, plasma reported in the current study were greater than those seen in another investigation also using a three-day loading protocol (BC+Bi, 1521 nmol·L -1 ; BC, 1102 vs. 334 nmol·L -1 ) (Bescos et al, 2012). However, we do acknowledge some anomalies with our data: the baseline levels of plasma [NO 2 -] were higher than that reported in other studies (~200-300 nM, (Hoon et al, 2014;Lansley et al, 2011)) and were only elevated for the TT in the case of the BC+Bi trial. Therefore, the difficulty in achieving a performance enhancement with the BC may reside with the inability of this dose to further raise the already high NO 2 -levels in our well-trained population.…”

“…We used protocols designed to achieve physiological changes favorable for high-intensity exercise lasting ~4-6 min (Hoon et al, 2014;Kilding et al, 2012). Specifically, our cyclists consumed chronic plus acute doses of NO 3 -rich beetroot crystals (300 mg NO 3 -per 15 g for three days and 15 g 1 hr preexercise) and a well-tolerated alkalizing protocol (0.3 g·kg BM -1 NaHCO 3 in five doses, commencing 2.5 hr preexercise) (Carr et al, 2011b).…”

“…We are not alone in failing to find performance benefits from either of the supplements examined in the current investigation. Others have failed to find ergogenic outcomes associated with NO 3 -supplementation in a similar cycling protocol in competitive cyclists (Hoon et al, 2014), or other exercise protocols of similar duration, such as a 1500-m run (Boorsma et al, 2014). The magnitude of plasma [NO 3 -]/[NO 2 -] increases (Hoon et al, 2014;Wilkerson et al, 2012;Wylie et al, 2013) and apparently different responses in highly-trained vs. lowercaliber athletes (Porcelli et al, 2015) may underpin these observations.…”

“…Others have failed to find ergogenic outcomes associated with NO 3 -supplementation in a similar cycling protocol in competitive cyclists (Hoon et al, 2014), or other exercise protocols of similar duration, such as a 1500-m run (Boorsma et al, 2014). The magnitude of plasma [NO 3 -]/[NO 2 -] increases (Hoon et al, 2014;Wilkerson et al, 2012;Wylie et al, 2013) and apparently different responses in highly-trained vs. lowercaliber athletes (Porcelli et al, 2015) may underpin these observations. Specifically, a lower proportion of Type II muscle fibers which are more responsive to NO 3 -supplementation, higher baseline NO 2 -status due to endogenous production via the NOS pathway, and better oxygenation of muscles in highly trained individuals may reduce the importance of an enhanced NO 3 -/NO 2 -/NO pathway (Jones, 2014b).…”

Nitric oxide and hypoxia at adaptation to muscular work (brief review)

“…В другом ис-следовании, проведенном на большой выборке ве-лосипедистов национальных сборных трех стран (26 чел. ), облегчающего воздействия NO 3 -при вы-сокоинтенсивном упражнении, моделирующем две 4-минутные гонки с интервалом 75 мин после прие-ма 70 мл СС (26 чел), найдено не было [49].…”