Dose dependent effects of dietary nitrate on the oxygen cost of moderate intensity exercise: Acute vs. chronic supplementation.
PURPOSE To investigate whether chronic supplementation with a low or moderate dose of dietary nitrate (NO3( reduces submaximal exercise oxygen uptake (V.O2) and to assess whether or not this is dependent on acute NO3( administration prior to exercise. METHODS Following baseline tests, 34 healthy subjects were allocated to receive 3 mmol NO3( 6 mmol NO3( or placebo. Two hours following the first ingestion, and after 7, 28 and 30 days of supplementation, subjects completed two moderate intensity step exercise tests. On days 28 and 30, subjects in the NO3( groups completed the test 2 h post consumption of a NO3( dose (CHR ACU) and a placebo dose (CHR) RESULTS Plasma nitrite concentration [NO2( was elevated in a dose dependent manner at 2 h, 7 days and 28 30 days on the CHR ACU visit. Compared to pre treatment baseline, 6 mmol NO3( reduced the steady state V.O2 during moderate intensity exercise by 3% at 2 h (P 0.06) 7 days and at 28 30 days (both P 0.05) on the CHR ACU visit, but was unaffected by 3 mmol NO3( at all measurement points. On the CHR visit in the 6 mmol group, plasma [NO2( had returned to pre treatment baseline, but the steady state V.O2 remained reduced. CONCLUSION Up to ~4 weeks supplementation with 6 but not 3 mmol NO3( can reduce submaximal exercise V.O2. A comparable reduction in submaximal exercise V.O2 following chronic supplementation with 6 mmol NO3( can be achieved both with and without the acute ingestion of NO3( and associated elevation of plasma [NO2(
Nitric oxide biology and chemistry