Dog Scratching Leg Reflex

Question
I was wondering why dogs sometimes involuntarily kick their hind leg when you scratch them vigorously in certain spots.  I am asking this because I have a 1-1/2 year old Beagle who has always kicked his leg when his stomach or ribs were scratched, but recently starting kicking his leg at even at the lightest touch to his lower back. Any thoughts?

Thanks, Adam  

Answer
Hey,

Dogs kick there legs because it feels good when you scratch them in certain parts. It's like you are massaging the area that you scratch them on. I scratch my Dog on his stomach sometimes and he always involuntarily kick his hind leg and when I stop scratching he starts licking my hand for me to stratch him again.

As far as  his lower back...maybe he could be hurting in his lower back. Does he seem to have problems with his lower back?

Vantressa Brown