Nitric oxide is a key molecule involved in vasodilation (the relaxation and widening of blood vessels to increase blood flow to tissues that lack oxygen or nutrients).[1][2] The beneficial effects of arginine on high blood pressure[3][4][5] and erectile dysfunction[6][7] are likely related to vasodilation because arginine increases nitric oxide synthesis.[1][2][8]
A similar mechanism may explain how arginine might increase VO2max.[9][10][11] Additionally, nitric oxide might have direct effects on muscle contractile function.[9][12] Furthermore, arginine’s role in the urea cycle helps with the excretion of ammonia[13], the accumulation of which might induce fatigue during exercise.[14][15][16]