Which factor explains why mean arterial pressure tends to rise only modestly during moderate aerobic exercise?

Which factor explains why mean arterial pressure tends to rise only modestly during moderate aerobic exercise?

• A. Cardiac output increases while systemic vascular resistance falls due to vasodilation in active muscles
• B. Cardiac output decreases and SVR increases
• C. Both CO and SVR increase proportionally to raise MAP dramatically
• D. There is no change in any parameter

Answer: (A)

Mean arterial pressure stays on a narrow range during moderate aerobic exercise because two opposing changes balance each other. Exercise causes the heart to pump more blood, so cardiac output rises. At the same time, the working muscles release metabolites that cause local vasodilation, lowering systemic vascular resistance. Since MAP is roughly the product of cardiac output and systemic vascular resistance, a higher CO tends to raise MAP, but the concurrent drop in SVR offsets that rise, producing only a modest increase in MAP. Additional adjustments from the baroreflex and redistribution of blood flow to active muscles help keep MAP stable.