Effect of acute nitrate ingestion on <(V)over dot>O2 response at different exercise intensity domains

While nitrate supplementation influences oxygen uptake (<(V)over dot>O-2) response to exercise, this effect may be intensity dependent. The purpose of this study was to investigate the effect of acute nitrate supplementation on <(V)over dot>O-2 response during different exercise intensity domains in humans. Eleven men ingested 10 mg.kg(-1) body mass (8.76 +/- 1.35 mmol) of sodium nitrate or sodium chloride (placebo) 2.5 h before cycling at moderate (90% of gas exchange threshold; GET), heavy (GET + 40% of the difference between GET and peak oxygen uptake (<(V)over dot>O-2peak), Delta 40) or severe (GET + 80% of the difference between GET and <(V)over dot>O-2peak, Delta 80) exercise intensities. Volunteers performed exercise for 10 min (moderate), 15 min (heavy) or until exhaustion (severe). Acute nitrate supplementation had no effect on any <(V)over dot>O-2 response parameters during moderate and severe exercise intensities. However, the <(V)over dot>O-2 slow amplitude (nitrate: 0.93 +/- 0.36 L.min(-1) vs. placebo: 1.13 +/- 0.59 L.min(-1), p = 0.04) and <(V)over dot>O-2 slow gain (nitrate: 5.81 +/- 2.37 mL.min(-1).W-1 vs. placebo: 7.09 +/- 3.67 mL.min(-1).W-1, p = 0.04) were significantly lower in nitrate than in placebo during the heavy exercise intensity. There was no effect of nitrate on plasma lactate during any exercise intensity (p > 0.05). Time to exhaustion during the severe exercise intensity was also not affected by nitrate (p > 0.05). In conclusion, acute nitrate supplementation reduced the slow component of <(V)over dot>O-2 only when performing heavy-intensity exercise, which might indicate an intensity-dependent effect of nitrate on <(V)over dot>O-2 response.