We have had our 9 month old hound mix for a short time now (he is a shelter dog). We have been walking/jogging him twice per day (40-60 minutes per walk). He was doing great on his walks - he almost always walks by my side, and rarely pulls on the leash (unless he sees a rabbit!!!). This past weekend, there were several times that he was refusing to walk anymore. The first time it happened, we were about 20 minutes into the walk. He began to stop, you know, sort of hung his head down low a little bit and began "digging in" to resist from going forward any further. I gently kept moving forward, somwhat ignoring him, and after a brief few seconds, he started trotting again by my side. He did the same thing yesterday morning. This happened immediately after we left the house. We got to the end of the driveway, walked about 20 feet down the street, and he started to dig in again. He just didn't want to walk any further. I reversed directions with him and we went the other way on the street. Well after going about 40 feet this time, he again started to "dig in" and didn't want to go forward any longer. Any thoughts on what might be causing this behavior and how to stop it?