Acute L-arginine supplementation reduces the O2 cost of moderate-intensity exercise and enhances high-intensity exercise tolerance
J Appl Physiol 109: 1394–1403, 2010. First published August 19, 2010; doi:10.1152/japplphysiol.00503.2010.—It has recently been reported that dietary nitrate (NO3) supplementation, which increases plasma nitrite (NO2) concentration, a biomarker of nitric oxide (NO) availability, improves exercise efficiency and exercise tolerance in healthy humans.
We hypothesized that dietary supplementation with L-arginine, the substrate for NO synthase (NOS), would elicit similar responses. In a double-blind, crossover study, nine healthy men (aged 19 –38 yr) consumed 500 ml of a beverage containing 6 g of L-arginine (Arg) or a placebo beverage (PL) and completed a series of “step” moderate- and severe-intensity exercise bouts 1 h after ingestion of the beverage. Plasma NO2 concentration was significantly greater in the Arg than the PL group (331 198 vs.159 102 nM, P 0.05) and systolic blood pressure was significantly reduced (123 3 vs. 131 5 mmHg, P 0.01).
The steady-state O2 uptake (V˙ O2) during moderate-intensity exercise was reduced by 7% in the Arg group (1.48 0.12 vs. 1.59 0.14 l/min, P 0.05). During severe-intensity exercise, the V˙ O2 slow component amplitude was reduced (0.58 0.23 and 0.76 0.29 l/min in Arg and PL, respectively, P 0.05) and the time to exhaustion was extended (707 232 and 562 145 s in Arg and PL, respectively, P 0.05) following consumption of Arg.
In conclusion, similar to the effects of increased dietary NO3 intake, elevating NO bioavailability through dietary L-Arg supplementation reduced the O2 cost of moderateintensity exercise and blunted the V˙ O2 slow component and extended the time to exhaustion during severe-intensity exercise.