Fig. 4. This figure demonstrates the hourly mean systolic blood pressure (mean ± SEM) in volunteers with or without oral arginine supplements. ANOVA testing demonstrated a significant difference during the treatment period (Hour 5:00 to Hour 14:00, i.e., 5:00 AM to 2:00 PM). The effect of arginine on systolic blood pressure was not significant until 7:00 AM. There was no difference between groups after arginine was discontinued (Hours 15:00 and 16:00). Please note that the arginine was stopped at hour 14:00 or 2:00 PM. The hypotensive influence was not present one hour after stopping the arginine for systolic measurements. A significant difference between the two groups at each time point by paired testing is indicated by a star (p < 0.05).