I've literally just created an account so I can respond to this thread. I know exactly the sensation about which you're talking and I don't believe it is anything spiritual and nor have I ever encountered another word to describe it. I feel it most in my calves and feet but, if I hold it for long enough ( and i struggle around the 10 sec mark) i feel it in my fingers and sinuses. It feels like opening up, so to speak. I have to consciously make it happen and if i do it a few times i usually have to 'recharge' to do it again. I'm amazed I've been able to find anyone talking about this so quickly via Google! I would love to find out more about it but it seems like something that is so obscure and impossible to quantify that there probably is no research on it. Glad to know I'm not alone.