My theory on the heart is that it isn't designed to move all the blood through the system, it depends on physical activity to squeeze blood along those tiny capillaries w/one-one valves. So ultimately if you don't do that a lot of exchange, wastes etc. doesn't get "flushed" out and any number of issues can arise, kinda like not changing the oil in your car, so it may cause a lot of those other conditions, eg, the basic body functions are not being supported by good circulation.