Effect of Acute Exercise on Plasma Nitric Oxide Level in Humans

Objective: Since nitric oxide (NO) plays an important role in regulating vascular tone and changes in the plasma concentration of the end product of NO (nitrite/nitrate) have been observed during exercise, we studied the influence of acute exercise on nitrite/nitrate plasma levels in a group of semiprofessional football players and in younger and older sedentary subjects. Methods: The subjects exercised for 10 min on a cycle ergometer and blood samples were obtained at rest and immediately after exercise. Plasma samples were analysed for nitrite/nitrate. Results: The acute physical exercise induced a significant increase in nitrite/nitrate plasma levels both in sedentary and in active subjects. No difference was evident between the younger and older subjects, both in the basal level and after exercise, indicating that the changes could not be due to age. The higher basal plasma level of nitrite/nitrate observed in the active subjects compared with sedentary groups indicates that the state of physical conditioning had an effect on resting NO concentration. Conclusion: It seems that either acute exercise, even for a short time, or training can induce an increase in circulating NO.