does your dog's back do that too?

My moms old cocker(since passed) would do that with her back if it tickled her, I never found it to be unusual.

This can acctuly be a indication of a health conditions of some sort. I don't remember exactly what it indicated but I remember my vet saying something about that. It shouldn't be something to worrie too much about. humm... I wish I remember what it was... like I said nothing serious but it does mean something... I'll have to look it up now.

I will have to check back and see what you find out.Emmie does this too,at the slightest touch.I have been wondering why.

Pretty commonly seen in females. If you look behind the bitch will probably tilt her pelvis and maybe even hook her tail as well.
 
Part of dog courtship is nuzzling of the ears, back, and flanks. It apparently feels quite good...lol. Most of my girls will move the skin on their back and tilt their pelvises when I rub them anyplace on their back behind the shoulders. They also look quite pleased...lol.

Oh I wanted to add that it makes sense for the back on a bitch to be an errogenous zone as it were, if you consider the position the male will eventually be in. If it feels kinda good while he's up on her back it encourages her to brace back against and hold his weight. I'd imagine even some male dogs might have this reponse since males and females of the human species share many errogenous zones.

Kayla did this and so does Bailey.  Only sometimes, in some spots.  The same spot doesnt always get a result either.  Generally I forget about it until the next time...   that makes sense Gina.  Hope its nothing to do with health as well..? 

If any of you have cats you are used to the skin moving thing lol. Both our cats like to "readjust" their back skins when you run your hands down them. lol.

My Chiropractor would adjust our female on occasion, when she needed it.  As I'm a licensed massage therapist, she shared with me that when the skin twitches laterally across the spine there is usually something going in there.
 
I specialize in animal massage and would suggest light massage along the spine in the area of question - ruling out anything serious going on first.  Dogs get sore like we do - with age, injury, and in just repetitively moving the wrong or right way - and then can establish a pattern of protecting that area via muscles, skin, and skeletal holding/tensing.
 
Goldens are known for having hip problems (which attach to the spine, everything is connected), so I massage and stretch mine regularly...paying attention to hot or warm areas, twitching, etc.  I'm already massaging and stretching our puppy...she naturally leans into the stretches.
 
When you know for sure that nothing serious is going on, I suggest circular massage - light to medium pressure - along both sides of the entire spine...not on top of spine.  Practice pressure on yourself first.  Small dogs, definitely light pressure.
 
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what you described I think is different than what I'm thinking about, easy to get thing confused without seeing them. I was thinking about how the vet lifts the skin of the back to check for dehydration and how if it crawls back into place means the dog is dehydrated. When Gina said cat's do it to I realized I was completly off.[&:] sorry.

Interesting. Can't say I 100% agree it's indicative of a problem "usually", esp in a young fit dog...sometimes I might go along with tho []
Since massaging your dog in that spot would doubtless make them quite happy so where's the harm in it lol!

ORIGINAL: rwbeagles

Can't say I 100% agree it's indicative of a problem "usually", esp in a young fit dog...sometimes I might go along with tho []

That's okay, you don't need to agree. []  Young fit dogs are especially prone to over doing activites, precisely because of their fitness.  As far as the Chiropractor and "usually" is concerned, the twitching she is looking for is confirmation of an area of the spine that needs to be adjusted.
 
For those interested, I want to point out that skin twitching, or crawling, can simply indicate an area that needs manual therapy.  This isn't a diagnosis I'm giving here, as it is not in my scope of practice.  It's just professional advice to tuck away. []

Actually, that is how I found out Romeo was allergic to fleas.  He was bitten by one, one! and whenever you would scratch him from the base of his tail up to the middle of his back, the poor thing would stretch, fall to the ground, or curve his back up or down, or lift his leg and try to scratch the other side.  Someone told me, I had found his "funny spot" but my dog did not seem like he was enjoying this too much, took him to the vet, tested him for fleas allergies and bingo same reaction.
 
Just food for thought.