Inorganic nitrate supplementation improves muscle oxygenation, O2 uptake kinetics and exercise tolerance at high but not low pedal rates
Bailey, Stephen J.; Varnham, Richard L.; DiMenna, Fred J.; et al.Breese, Brynmor C.; Wylie, Lee; Jones, Andrew M.
Date: 9 April 2015
Publisher
American Physiological Society
Publisher DOI
Abstract
We tested the hypothesis that inorganic nitrate (NO3-) supplementation would improve muscle oxygenation, pulmonary O2 uptake (VO2) kinetics and exercise tolerance (Tlim) to a greater extent when cycling at high compared low pedal rates. In a randomized, placebo-controlled, cross-over study, seven subjects (mean ± SD, age 21 ± 2 yr, ...
We tested the hypothesis that inorganic nitrate (NO3-) supplementation would improve muscle oxygenation, pulmonary O2 uptake (VO2) kinetics and exercise tolerance (Tlim) to a greater extent when cycling at high compared low pedal rates. In a randomized, placebo-controlled, cross-over study, seven subjects (mean ± SD, age 21 ± 2 yr, body mass 86 ± 10 kg) completed severe-intensity step cycle tests at pedal cadences of 35 rpm and 115 rpm during separate 9 day supplementation periods with NO3--rich beetroot juice (BR; providing 8.4 mmol NO3-∙day-1) and placebo (PLA). Compared to PLA, plasma nitrite concentration increased 178% with BR (P<0.01). There were no significant differences in muscle oxyhemoglobin concentration ([O2Hb]), phase II VO2 kinetics or Tlim between BR and PLA when cycling at 35 rpm (P>0.05). However, when cycling at 115 rpm, muscle [O2Hb] was higher at baseline and throughout exercise, phase II VO2 kinetics was faster (47 ± 16 s vs. 61 ± 25 s; P<0.05) and Tlim was greater (362 ± 137 s vs. 297 ± 79 s; P<0.05) with BR compared to PLA. These results suggest that short-term BR supplementation can increase muscle oxygenation, expedite the adjustment of oxidative metabolism and enhance exercise tolerance when cycling at a high, but not a low, pedal cadence in healthy recreationally-active subjects. These findings support recent observations that NO3- supplementation may be particularly effective at improving physiological and functional responses in type II muscle fibers.
Institute of Biomedical & Clinical Science
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