Abstract

Controversy exists whether recruitment of a large muscle mass in dynamic exercise may outstrip the hearts pumping capacity and require neurogenic vasoconstriciton in exercising muscle to prevent a fall in arterial blood pressure. To elucidate this question, 7 healthy young men cycled for 70 min at 55-60 VO2max. At 30 to 50 min, arm cranking was added and total work load increased to 82+-4 VO2max. During leg exercise, leg blood flow averaged 6.15+-.51 l/min, mean arterial blood pressure 137+-4 mmHg and leg conductance 42.3+-2.2 ml/min/mmHg. When arm cranking was added to leg cycling, leg blood flow did not change significantly, mean arterial blood pressure increased transiently to 147+-5 mmHg and leg vascular conductance decreased transiently to 33.5+-3.1 ml/min/mmHg. Furthermore, arm cranking doubled leg noradrenaline spillover. When arm cranking was discontinued and leg cycling continued, leg blood flow was unchanged but mean arterial blood pressure decreased to values significantly below those measured in the first leg exercise period. Furthermore, leg vascular conductance increased transiently, and noradrenaline spillover decreased towards values measured during the first leg exercise period. It is concluded that addition of arm cranking to leg cycling increases leg noradrenaline spillover and decreases leg vascular conductance but leg blood flow remains unchanged because of a simultaneous increase in mean arterial blood pressure. The decrease in leg vascular conductance seems to be a means to prevent overperfusion. Verf.-Ref.