Blood flow circulation must be redistributed in the human body at the onset of dynamic exercise to deliver an appropriate amount of oxygen to exercising muscles. Muscle sympathetic nerve activity (MSNA) has been recognized as a major regulator of blood flow redistribution. However, recent research has indicated that there are some potent substances that affect peripheral blood flow circulation in humans. This review focuses on the physiological significance of functional sympatholysis, which can occur in exercising muscles, and the role of some potent vasoconstrictors in determining how blood flow in humans is redistributed during heavy exercise. It is expected that, during heavy exercise that requires marked blood flow redistribution (i.e. endurance sports), the maximal blood flow is enhanced as a function of the individual's maximal cardiac output (Q_max) by chronic exercise. This will contribute to overall muscle performance.