It has recently been reported that dietary nitrate supplementation which increases plasma nitrite concentration, a biomarker of nitric oxide (NO) availability, improves exercise efficiency and exercise tolerance in healthy humans. We hypothesised that dietary supplementation with L-arginine, the substrate for nitric oxide synthase (NOS), would elicit similar responses. In a double-blind, crossover study, nine healthy males (aged 19-38 years) consumed a 500 mL beverage containing 6 g of L-arginine (ARG) or a placebo beverage (PLA), and completed a series of 'step' moderate-intensity and severe-intensity exercise bouts 1 h post-ingestion. Plasma [nitrite] was significantly greater following L-arginine consumption compared to placebo (ARG: 331 ± 198 vs. PLA: 159 ± 102 nM; P<0.05) and systolic blood pressure was significantly reduced (ARG: 123 ± 3 vs. PLA: 131 ± 5 mmHg; P<0.01). The steady-state VO2 during moderate-intensity exercise was reduced by 7% in the ARG condition (ARG: 1.48 ± 0.12 vs. PLA: 1.59 ± 0.14 L•min-1; P<0.05). During severe-intensity exercise, the VO2 slow component amplitude was reduced (ARG: 0.58 ± 0.23 vs. PLA: 0.76 ± 0.29 L•min-1; P<0.05) and the time-to-exhaustion was extended (ARG: 707 ± 232 s vs. PLA: 562 ± 145 s; P<0.05) following ARG. In conclusion, similar to the effects of increased dietary nitrate intake, elevating NO bioavailability through dietary L-arginine supplementation reduced the O2 cost of moderate-intensity exercise and blunted the VO2 slow component and extended the time-to-exhaustion during severe-intensity exercise.
- O2 uptake
- Copyright © 2010, Journal of Applied Physiology