Bolus L‐arginine supplementation in the fed state at rest and following resistance exercise does not effect bulk muscle blood flow

The release of nitric oxide from the vascular endothelium results in vasodilation, which in turn increases local blood flow. Although it is known that L‐arginine is the primary substrate for nitric oxide synthase (the enzyme responsible for nitric oxide production) the effect of a bolus oral dose of L‐arginine on blood flow has not previously been studied. The present study was designed to elucidate the effects of post‐exercise L‐arginine intake on femoral artery blood flow. Eight healthy, recreationally active male subjects (22.0±2.1 yr, BMI=24.0±2.6 kg/m 2 ) participated in two trials in a randomized, double‐blind manner. Each trial consisted of a bout of leg resistance exercise followed by the consumption of a drink containing 10g of essential amino acids and either 10g L‐arginine (ARG) or an isonitrogenous amount of glycine as a control (CON). Femoral artery blood flow was measured at rest and for 3 h post‐exercise using Doppler ultrasonography at the femoral artery. Despite a 4‐5‐fold increase in blood L‐arginine concentration in the ARG condition (P<0.01), no differences in blood flow were observed between the ARG and CON conditions. Hence, we conclude that exogenous L‐arginine intake does not influence bulk post‐resistance exercise hyperemia. Supported by NSERC.