L-Arginine supplementation does not enhance blood flow and muscle performance in healthy and physically active older women.

Purpose: The purpose of this study was to examine the effects of acute L-arginine (L-arg) supplementation on peripheral vasodilatation and muscle performance in older women.

Methods: In a double-blind, randomized, placebo-controlled study, 20 elderly women were randomly assigned in a double-blind fashion to either an L-arg (ARG, N = 10) or placebo (PLA, N = 10) group. During the first visit, both groups underwent a Doppler ultrasound exam (to assess the femoral artery vasodilatation) at rest (baseline), and immediately before and after the isokinetic strength test (performed at 80 min after supplementation). On the second and third visits, the groups completed a battery of muscle performance tests (to assess the isometric and functional strength), initiated at the same time point (80 min after supplementation).

Results: The femoral artery blood flow (ARG: 443.9 ± 42.8 vs. PLA: 373.1 ± 40.8 ml/min; P > 0.05) and area (ARG: 0.45 ± 0.03 vs. PLA: 0.41 ± 0.02 cm(2); P > 0.05) were similar between the groups at basal conditions, and they remained unchanged after supplementation. Following exercise, blood flow increased ~160 % above the basal level, and there was no significant (P > 0.05) difference between the ARG and PLA groups. Additionally, there were no significant (P > 0.05) differences between the ARG and PLA groups for any strength variable (isokinetic, isometric, and functional).

Conclusion: These results show that acute L-arg supplementation provides no ergogenic effect on blood flow and muscle performance in older women.