Most dogs enjoy a good belly rub or tummy tickle. They’ll lie on their backs and literally beg for it. But why do certain spots get their legs kicking too?
This happens when you hit the “sweet spot”. What happens physiologically may a little surprising. Your dog’s not actually ‘besides themselves” with pleasure, but there is a bit of “it’s so nice that I can’t stand it” going on.
Some dogs have a few “sweet spots” that will get their legs going. For most dogs, the spot is in the saddle region – the belly, sides, and a few places on the back.
Some dogs kick only one leg, while some kick both. The height and speed varies depending on the spot and sensitivity.
Animal Planet offers this explanation:
Dogs shake or kick their legs when you scratch them because of something known as the scratch reflex. It’s a completely involuntary reaction, which explains why your dog may look as puzzled as you do when it starts to happen. When you scratch or tickle your dog’s belly, it irritates him, much the same way that the wind or a bug might. It activates nerves under his skin that are connected to his spinal cord and relays a message to his leg muscles to kick in an attempt to get rid of the irritant. Of course, you’re the one both providing the “itch” and “scratching” it, so it’s a completely pointless act.
So actually, you’re kind of irritating your dog. The scratch reflex is an entirely automatic reaction,. The strangest part is that this entirely automatic response comes about during an activity that your dog really loves. This is why your dog might seem as confused as you do when it starts. The best thing to do is to simply move to another spot and the kicking should stop.
Veterinarians make use of the sensitive area to recognize nerve damage or neurological problems. The belly-rub kick is similar to the human knee-jerk when tapped just under your knee with a hammer, or a cat’s instant tail-lift if you scratch the root of the tail.
The majority of dogs absolutely love a stomach scratch. It they didn’t they’d soon let you know. Don’t stop this wonderful, loving activity, simply move on to a more appropriate place.