Study aim: To determine the effects of oral L-arginine supplementation on vasodilation, blood flow and maximum oxygen uptake (O₂max) in soccer players.

Material and methods: A group of 24 healthy male soccer players aged 20 - 26 years volunteered to participate in the study. The subjects were randomly assigned into 3 groups: experimental, placebo and control. Experimental group was given L-arginine (6 g orally) and the placebo group - starch (6 g orally) daily for a week; subjects from the control group remained untreated. Before the test and at the end of the week blood samples were collected, and systemic blood pressures, blood flows and maximal oxygen uptake (O₂max, by Queens College step test) were recorded. Blood samples were assayed for HDL, LDL, triglyceride and urea concentrations. The study was conducted in a randomised, single-blinded, placebo-controlled fashion consisting of 7-day treatment periods.

Results: Oral supplementation of L-arginine significantly (p<0.01) decreased blood pressure indices and increased O₂max (p<0.01), blood flow (p<0.05), femoral artery diameter (p<0.05) and urea levels (p<0.05). There was no change in blood lipid levels (p<0.05). No significant changes were noted in the placebo and control groups.

Conclusions: Oral supplementation of L-arginine may have beneficial effect on vasodilation and O₂max, therefore may increase the exercise capacity of soccer players.