In this randomized, double-blind, placebo-controlled trial, 40 participants with hypertension were given 6 g of citrulline malate acutely with exercise, exercise with placebo, no exercise with citrulline, or no exercise with placebo.
At rest, there wasn't an overall notable effect of citrulline on blood, although blood pressure was somewhat higher, and was statistically significantly higher at one point. During exercise, however, the overall reduction in systolic blood pressure, but not diastolic blood pressure, was increased by citrulline acutely. During the 24 hour period, there was a greater reduction in systolic and diastolic blood pressure in the citrulline groups, but it was only statistically significant for diastolic blood pressure. There weren't any statistically significant effects on heart rate variability.