What does this sensation signify - if anything??

[carbar]

I have an exercise I do usually when lying in bed, and that is to try and move my toes/feet. I am T4 complete so don't expect to move anything! but the concentration & effort of trying produces a strong sensation like a rush of energy down my legs, particularly the back of the legs, as far as my feet. It is not random, but occurs in both legs every single time I make the effort. I try to make it happen in one leg at a time too but this is not so clear. The left seems more dominant. What exactly is happening when I do this, is there actually something physically taking place in the legs or is it somehow something more to do with my brain willing it to happen? It is a curiously pleasant sensation partly I suppose because it is the only one that appears to be "connected" - i.e. I can make it happen. All other sensations/pain appear not to have a connection. One other thing, the only other time I get this sensation is if I hear an unexpected loud noise - then I get it very strongly behind both knees. Sort of like an adrenalin rush.
Any explanations? Thanks.

[pianodave]

I recommend checking out the thread titled "Leg Pain" earlier in this forum. It appears to deal with your specific sensation of electric shocks behind your knees.

Hope it helps.

[carbar]

yes, I saw that thread after I had posted mine. I see that there are others who have the same type of sensation, but I didn't see any post there giving a shot at an explanation of what is exactly happening when these sensations occur - whether there is actually a physical response in the legs or whether it is somehow just the work of the brain?