Andrew Huberman· PhD
But in addition, because of the amount of blood that's being returned to the heart, when you engage in these really intense bouts of effort repeatedly, the amount of blood being returned to the heart actually causes an east centric loading of one of the muscular walls of the heart. So your heart is muscle. It's cardiac muscle. We have skeletal muscle attached to our bones and we have cardiac muscle, which is our heart. When more blood is being returned to the heart because of the additional work that your muscles and nerves are doing, it actually has the effect of creating an east centric loading, a kind of pushing of the wall, the left wall. I realize I'm not using the strict anatomy here, but I don't want to get into all the features of the structural features of the heart. But the left ventricle essentially getting slammed back and then having to push back in a kind of east centric loading of the cardiac muscle and the muscle thickens, but not because the heart thickens overall, it's actually a strengthening of the cardiac muscle in a way that increases what we call stroke volume.