Long-term effects of NO 3– on the relationship between oxygen uptake and power after three weeks of supplemented HIHVT

Abstract

The aim of this study was to investigate the later effects of daily NO 3– supplementation over 3 wk of training on the relationship between O2 uptake and power at different intensities with an incremental test (IT), a double-wingate test (WT), and an endurance capacity test at 80% Wmax (ECT) before and after the supplementation period. Seventeen male recreational athletes participated in this double-blind placebo (PL)-controlled study. Subjects participated in a 3-wk intermittent high-intensity, high-volume training period with 45 intervals of Wmax 10 W and an active recovery period of 10 W in between with dietary NO 3– (NaNO3) or placebo supplementation (NaCl) (both 8.5 mg·kg 1 ·day 1 ) on a cycle ergometer. During a training session, plasma [NO 3– ] (P 0.001) and plasma [NO 2– ] (P 0.01) were higher in nitrate (N), whereas in pre- and posttests mean plasma [NO 3– ] and [NO 2– ] were not different between groups. In the WT [48 h after cessation of supplementation (C)], the ratio between V O 2 and power decreased in N (P 0.01) with no changes in PL. Endurance capacity (4 –5 days after C) similarly increased in both groups (P 0.01). However, the total oxygen consumption decreased by 5% (P 0.01) in N, with no change in PL. The slope of V O 2 ·W 1 in IT (5–7 days after C) decreased in N (P 0.01), whereas no changes were found in PL. During low- and moderate-intensity workloads, no changes and differences in V O2 could be detected. We conclude that nitrate supplementation causes a sustaining reduction of the oxygen cost per watt during exercise with a large recruitment of type II muscle fibers without affecting endurance capacity.