In mainstream medicine they claim that we need to move the body in order to make the blood flow. They say that the blood vessels need to be squeezed by muscle movements outside the vessels because they lack the capacity to transport the blood fully themselves [correction: mainstream medicine has now changed its opinion about that! See below.]. That's actually a false claim since there are meditators who can sit perfectly still for hours with only their breathing moving.
And it's even probable that the belief that the heart is doing all the pumping of the blood is contributing a lot to increasing cardiovascular disease in our modern society. The blood vessels, except for the tiniest, the capillaries, have muscles in their walls. So with the correct neurological functioning the blood vessels can transport the blood themselves, even when the body is still, and the heart just gently needs to squeeze blood into the elastic aorta in order to maintain a balanced pressure.
Wow, I found on Wikipedia that mainstream medicine has now realized this:
"There is a layer of muscle surrounding the arteries and the veins which help contract and expand the vessels. This creates enough pressure for blood to be pumped around the body. Blood vessels are part of the circulatory system, together with the heart and the blood." -- https://en.wikipedia.org/wiki/Blood_vessel
Ok, that's good. But still we can improve the blood flow by making our nervous system better regulate the blood vessel musculature (and even the capillaries, because as one scientific study showed, the cells in the brain slightly push and pull on the capillaries to regulate the blood flow).
The old mainstream theory was that so-called venous pumps were always needed to make the blood flow fully:
"Blood is pushed through the veins when body muscles contract and squeeze the veins. In this way the blood moves.
The contraction/relaxation cycles of skeletal muscles squeeze the veins forcing the contained blood towards the heart." -- http://leavingbio.net/circulatory%20sys ... system.htm
So, to come to the point, the cardiovascular system has a lot of tensions within it. And the idea is that dissolving those tensions can be done by changing our beliefs about how the heart and the blood vessels work. Instead of thinking of the heart as a pump and the blood vessels as passive tubes, think of the whole cardiovascular system as a unified and active system.