We had a very large Boxer (around 110lbs) and no matter what we did he would pull. What worked for us was called a Halti..Its a collar that also loops around the muzzle. When they pull it tugs their head down and to the side. It doesnt hurt them either. They can still eat, drink and bite it they want to. But alot of people thought he had a muzzle on. He was the only one of the 5 Boxers we have had that had that issue.. http://www.petsupplies4less.com/Halti-Headcollar_p_1157.html?preselopt=8935&gclid=CK24-dPihMsCFQtFaQodl5cHMA