Why do woman swing their leg put a bet on and fourth when they own their legs crossed?

I notice when woman enjoy their legs crossed they will swing the leg that is crossed over the other leg actual fast.It is sexy.I be just wondering why woman do that and why dont most men do that.Why do woman swing their leg put a bet on and fourth when they own their legs crossed?
I agree that it's a unconscious way of keeping the blood blood flowing and not getting numb. Women probably don't even assume about it. The just other way would be to hang on to switching legs. Men, on the other hand, don't usually cross their legs so tightly; they do that cross at the ankle position. That's smaller amount constrictive. Even if they do use the leg cross, men are more aware of any position or movement that is "unmasculine" and they avoid those. At lowest in Western culture.
resourcefully its how they cross it...it gives leg cramps i deem
I do it so my leg doesn't fall asleep! It's not a conscious entry... just inborn habit. My foot starts to tingle if I stay approaching that too long... swinging my leg keeps it from falling asleep! I don't know why guys don't do that... worthy question.
To avoid reflective vein thrombosis and varicose vein (gosh, hope that doesn't ruin all the sexiness for ya)
to some, doing so releases tension