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Controlled Clinical Trial
. 2017 Mar 1;122(3):642-652.
doi: 10.1152/japplphysiol.00909.2016. Epub 2016 Dec 1.

Influence of Dietary Nitrate Supplementation on Physiological and Muscle Metabolic Adaptations to Sprint Interval Training

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Free PMC article
Controlled Clinical Trial

Influence of Dietary Nitrate Supplementation on Physiological and Muscle Metabolic Adaptations to Sprint Interval Training

Christopher Thompson et al. J Appl Physiol (1985). .
Free PMC article

Abstract

We hypothesized that 4 wk of dietary nitrate supplementation would enhance exercise performance and muscle metabolic adaptations to sprint interval training (SIT). Thirty-six recreationally active subjects, matched on key variables at baseline, completed a series of exercise tests before and following a 4-wk period in which they were allocated to one of the following groups: 1) SIT and [Formula: see text]-depleted beetroot juice as a placebo (SIT+PL); 2) SIT and [Formula: see text]-rich beetroot juice (~13 mmol [Formula: see text]/day; SIT+BR); or 3) no training and [Formula: see text]-rich beetroot juice (NT+BR). During moderate-intensity exercise, pulmonary oxygen uptake was reduced by 4% following 4 wk of SIT+BR and NT+BR (P < 0.05) but not SIT+PL. The peak work rate attained during incremental exercise increased more in SIT+BR than in SIT+PL (P < 0.05) or NT+BR (P < 0.001). The reduction in muscle and blood [lactate] and the increase in muscle pH from preintervention to postintervention were greater at 3 min of severe-intensity exercise in SIT+BR compared with SIT+PL and NT+BR (P < 0.05). However, the change in severe-intensity exercise performance was not different between SIT+BR and SIT+PL (P > 0.05). The relative proportion of type IIx muscle fibers in the vastus lateralis muscle was reduced in SIT+BR only (P < 0.05). These findings suggest that BR supplementation may enhance some aspects of the physiological adaptations to SIT.NEW & NOTEWORTHY We investigated the influence of nitrate-rich and nitrate-depleted beetroot juice on the muscle metabolic and physiological adaptations to 4 wk of sprint interval training. Compared with placebo, dietary nitrate supplementation reduced the O2 cost of submaximal exercise, resulted in greater improvement in incremental (but not severe-intensity) exercise performance, and augmented some muscle metabolic adaptations to training. Nitrate supplementation may facilitate some of the physiological responses to sprint interval training.

Keywords: beetroot juice supplementation; exercise training; muscle metabolism; training adaptation.

Figures

Fig. 1.
Fig. 1.
Mean ± SD resting plasma [NO3] (A) and plasma [NO2] (B) responses in SIT+BR (solid black line), SIT+PL (solid grey line), and NT+BR (dashed black line). *Different from preintervention (P < 0.05); †different from midintervention (P < 0.05); ‡different from SIT+PL (P < 0.05).
Fig. 2.
Fig. 2.
Mean ± SD changes (Δ) in peak WR at midintervention and postintervention in the three groups expressed relative to preintervention baseline. The change in peak WR from preintervention to postintervention was greater in SIT+BR (solid black line) than in SIT+PL (solid grey line) and NT+BR (dashed black line). *Different from preintervention (P < 0.05); †different from midintervention (P < 0.05); #different from NT+BR (P < 0.05); ‡different from SIT+PL (P < 0.05).
Fig. 3.
Fig. 3.
Mean ± SD blood [lactate] at rest (black bars), at 1 min (patterned bars), at 3 min (grey bars), and at task failure (open bars) during severe-intensity exercise. *Different from preintervention (P < 0.05).
Fig. 4.
Fig. 4.
Mean ± SD muscle [lactate] (A), muscle pH (B), and muscle [glycogen] (C) at rest (black bars), at 3 min (grey bars), and at task failure (open bars) during severe-intensity exercise. d.w., Dry weight. *Different from preintervention (P < 0.05); #different from postintervention NT+BR (P < 0.05); ‡different from postintervention SIT+PL (P < 0.05).

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