extensor
The blood flows to and from the heart primarily because of the relaxing and contracting of the heart muscle. Muscles throughout the body also exert pressure on blood vessels to literally push blood to the heart.
the relaxing and contracting of the heart muscle
knee
Henry Knox and his men volunteered to bring the cannons from Fort Ticonderoga back to Boston in 1775. Knox used ox sleds to bring 50 captured cannons back to Boston.
arerobic
I
Normally yes, but doctors sometimes prescribe light exercise to help improve the function of a heart that may not be working normally.