It has well known that post-exercise hypotension (PEH) after a bout of aerobic exercise was a major mechanism to reduce blood pressure though exercise training, and that citrulline supplementation reduced blood pressure by increasing nitric oxide in vivo. However, the effects of citrulline supplementation on PEH have not been fully elucidated yet. This study was designed to examine the effects of citrulline supplementation on PEH after a bout of aerobic exercise in prehypertensive and normotensive 20s males. The effects of a four-day citrulline or placebo treatment on blood pressure, cardiovascular function, and blood lactate concentration measured at rest and during recovery phase after a bout of exercise performed for 30 min at 70% VO2max were compared and analyzed. All subjects participated in a citrulline trial and a placebo trial repeatedly according to a counter-balanced order. Main results of the present study were as follows: 1) Systolic blood pressure, diastolic blood pressure, and mean arterial pressure measured at 10-60 min of recovery phase in citrulline trial were significantly lower than placebo trial. Rate-pressure product measured at 30 min and 45 min of the recovery phase in citrulline trial was significantly lower than placebo trial. 2) No significant differences were found in heart rate (HR), cardiac output (CO), and total peripheral resistance (TPR) measured during the recovery phase between two trials. There were significant differences in HR, stroke volume, CO, and TPR among times within a trial. 3) No significant difference was found in blood lactate concentration measured at rest and during the recovery phase between two trials. The results would be summarized that the PEH was augmented by the citrulline supplementation, and that burden to cardiac muscle as well as cardiovascular function were not affected by the citrulline supplementation. It was concluded that the short-term citrulline supplementation would be very effective to augment the PEH. A research investigating the effects of citrulline supplementation on the PEH in pre-hypertensive and/or hypertensive individuals would be warranted. In addition, a study examining the effects of citrulline supplementation during long-term exercise training on the blood pressure in hypertensive patients also would be warranted in near future.
