After exercise, peripheral arteries typically show which change in resistance?

• A. Low resistance
• B. High resistance
• C. No change
• D. Reversed flow

Answer: (A)

Local metabolic regulation causes arterioles in active muscles to dilate after exercise, a process known as functional hyperemia. The working muscles produce metabolites (low O2, high CO2, H+, adenosine, potassium) that relax smooth muscle and release endothelium-derived relaxing factors like NO, so the peripheral arterial bed becomes less resistant. With this vasodilation, more blood can flow to meet the increased metabolic demand, and the Doppler waveform shifts toward a low-resistance pattern with a stronger diastolic component. This is in contrast to resting conditions, where resistance is higher and diastolic flow is reduced. Reversed flow or no change would not reflect the active vasodilation that occurs with exercise.