Bull dog mix won't sit

Pushing a dog's butt down just engages the oppositional reflex.  If the dog has been cleared by a vet, and has no physical problem that makes it painful for him to sit, then I would learn to clicker train, and "capture" the behavior when he sits on his own, or reward him for approximations of the behavior - in other words, if he even ducks his butt a bit, it earns him a click and a treat.
For more on clicker training, and "shaping" behaviors, visit these sites:
www.clickerlessons.com
www.clickertraining.com (there's a trainer search on this site)
www.clickertrainusa.com
www.clickersolutions.com

Attempting to position the dog may just trigger an oppositional reflex in him - picture someone you don't know grabbing your arm, your first reflex - especially if you are distrustful or dislike being touched - is to pull your arm back. The other problem with that method is that, especially with a dog whose health problems you don't yet know, he could actually be protecting himself from pain due to HD or something like that.
 
You should probably assume the dog has no idea what "sit" means... you have to teach him what it means. The two ways I would suggest teaching it are luring and capturing. Capturing means, anytime you catch him sitting (and surely he sits sometimes?), praise him, tell him "good sit!" and give him treats or rewards (whatever turns him on most). Luring a sit is done by offering a treat (or toy if he likes toys) in front of his face, then slowly moving it (hang on tight to it!) back over the top of his head, just inches away from his face. Most dogs will automatically drop their butts to the floor as they try to follow the treat back behind their heads. The moment he sits you tell him "good sit!" treat and praise.
 
Good luck and congrats on rescuing this boy!

Thank you. the vet has given him a clean bill of heath upon completion of his on going treatment. I will give this a try. The Lokota proverb was right, don't know what I was thinking.
thanks again

Get close to a barrier (like a piece of upholstered furniture).  Position the dog so its rear is up against the furniture.  Take a treat (a really good treat) in your hand.  Place your hand at nose level and slowly raise the treat up (with the nose following) and slightly behind the dog's head.  The dog will crane its neck up.  As the becomes less comfortable (craning the neck to follow the treat) the dog will sit to change the position of the spine so it is more comfortable.  Say "sit" use a word to indicate yup that is it (like good dog).  Repeat over a couple of days and in new locations in the house and you will have the beginning of a sit on command. 

ORIGINAL: mrv

Get close to a barrier (like a piece of upholstered furniture).  Position the dog so its rear is up against the furniture.  Take a treat (a really good treat) in your hand.  Place your hand at nose level and slowly raise the treat up (with the nose following) and slightly behind the dog's head.  The dog will crane its neck up.  As the becomes less comfortable (craning the neck to follow the treat) the dog will sit to change the position of the spine so it is more comfortable.  Say "sit" use a word to indicate yup that is it (like good dog).  Repeat over a couple of days and in new locations in the house and you will have the beginning of a sit on command. 

This technique works well against a corner between two walls, too. []

I agree, even thought of that one...Just thought in the off chance that made the dog a bit nervous, butt up against the couch would have a whole different "feel" to it. []

Here's a funny story you can relate tone of my client's was given a young Pit mix by a hispanic guy that was sitting on a wall near my client's place of business. My client was outside smoking a cigarette and saw this man with the dog and commented on how good looking the pup was. The hispanic guy didn't speak English so my client went back in the building. The next day my client was visited by the hispanic guy with pup in tow and a bag of dog food. He handed over the dog and dog food to my client and walked away. Fast forward...my client tried teaching the dog to "sit" for weeks but to no avail. His daughter put two-and-two together and told the dog in Spanish to "sit" and the dog sat.Maybe your dog doesn't understand English!

I'm not sure if he was raised out side, but dosn't seem like he was pet alot. He was slightly timid. He still likes to know where your hands are going. He Is so bright eyed and attentive and he plays very well with my 3 year old 50lb 1/4 chow, 1/4 collie, 1/4 ridge back...sorry other 1/4 unknown. He stands very tall and proud. He likes my cat and my 6lb poodle mix. He makes me laugh.
 
Just though I would share a little

That is so funny... might give it a try. I sure am glad I have met all of you. I just have always loved my dogs. Three is my limit! Now that I have found this guy am quite the happy girl.
 
I was once walking and a black lab began following about 10 ft behind me. I would turn and tell him to get...and he would sit. I would continue walking, he would follow...I'd say get... he would sit. He and I had a nice walk togeather.

ast forward...my client tried teaching the dog to "sit" for weeks but to no avail. His daughter put two-and-two together and told the dog in Spanish to "sit" and the dog sat.Maybe your dog doesn't understand English!

Oh what a funny story!

Reminds me of my childhood, I'm hispanic and my grandparents mostly speek spanish. As a kid they always told us to "sit down" in spanish when we were being a little too hyper. Somehow when my parents told us "sit down" in english it never worked. Even though I can't speek spanish I was taught a few words in spanish first before I learned english becaue of my grandparents. Guess you could apply the same to dogs as well?

Just remember that in Spanish "to sit" is a verb and you have to conjugate it to sound correct depending on weather your talking in first, second or third person and in singular or plural...that tricky spanish...[]

ORIGINAL: ldyharley

Here's a funny story you can relate tone of my client's was given a young Pit mix by a hispanic guy that was sitting on a wall near my client's place of business. My client was outside smoking a cigarette and saw this man with the dog and commented on how good looking the pup was. The hispanic guy didn't speak English so my client went back in the building. The next day my client was visited by the hispanic guy with pup in tow and a bag of dog food. He handed over the dog and dog food to my client and walked away. Fast forward...my client tried teaching the dog to "sit" for weeks but to no avail. His daughter put two-and-two together and told the dog in Spanish to "sit" and the dog sat.Maybe your dog doesn't understand English!

Don't laugh - my assistant trainer adopted a Sato from Puerto Rico and although the dog understands her English commands, she understands a bit of Spanish. []

I had a bilingual cat.  I was learning Vietnamese and started using it to teach the cat to "come" when called.