Blood Pressure
It is a simple fact from fluid dynamics that for a fluid flowing through a pipe, a higher fluid speed means a lower pressure in general. This is called the 'Bernoulli |Effect', and arises from the Bernoulli equation for a flowing fluid.\[p+ \frac{1}{2} \rho v^2 + \rho gh= constant\]
where
\[p= pressure, \; \rho = density, \; v= fluid \; speed, \; g=9.81m/s^2, \; h=height \]
If the fluid is flowing horizontally we can write
\[p+ \frac{1}{2} \rho v^2 = constant\]
The Bernoulli Effect explains why having a strong heart that pumps efficiently will generally result in a lower blood pressure. The heart is a pump. If it can pump more strongly, the blood will flow faster and blood pressure will fall as a result of the Bernoulli effect.
Blood pressure is important because high blood pressure can cause kidney failure and heart problems. The muscles of the heart can be strengthened by exercise, as with any muscles.