If the apex of the heart is not working properly it is as a result of the congestive heart failure. This usually requires immediate medical attention and dietary changes.
extensor
increased agility
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
moderate
knee
more than 6 mets
vigorous
it would be light