That feeling

Ok here's a description of that feeling. This is purely for my own reference, that i may not forget it's details. It starts somewhere in the heart (which is by this time beating quite fast). Somehow a band or a beam of sorts slowly travels downward from the chest area. The beam is characterized by a sensation not quite akin to pain, but is more like a "weakness". Perhaps this weakness is best described as, "that same feeling Superman gets when exposed to kryptonite". Anyway, this beam slowly travels downward, and is felt strongest when it reaches the knees, where it seems to linger on for a while, before proceeding lower and ultimately diminishing towards the feet.