When you do aerobic exercise like running or cycling, it pushes blood through your vessels in a way that helps your blood vessels make a substance called nitric oxide. This substance helps your blood vessels relax and widen, which lowers your blood pressure.

Aerobic exercise induces shear stress on blood vessel walls, stimulating endothelial nitric oxide production, which results in sustained reduction in vascular resistance.

When the lining of blood vessels isn't working right and makes less of a substance that keeps vessels open, it can raise blood pressure — even if the heart's pumping and blood amount stay the same.