I have a 4 month old staff. Every time I put his harness on and lead he will not walk outside. He walks fine off the lead in the park, he is lead trained. Its not the lead or harness that's the problem. Its when I try leave the house to walk to the park he just stands there and does not move, but is fine in the park etc. what can I do?

Are you firmly Alpha in his mind? I don't believe dogs are stubborn because this would mean they plan and hold a grudge which they don't. He is showing some level of fear or at least wariness about going outside. You must win this little battle even if you use treats to get him moving. What type of collar do you use?

Don't allow your pup to call the shots!

I'm not a fan of harnesses. They enable dogs to pull. The only reason he is not pulling right now is because he is just a puppy.

Your pup is not walking out because you're not taking the time to teach him how to walk on a leash. Dogs will naturally follow their owner, but if you're not giving him the environment to follow, this is what happens. Its nothing you are doing right or wrong, but you do need to make "class" time for him throughout the day. 15 minutes a day is all you need. During that time, put continuous pressure on his lead until he moves. Even if it's a step forward, its still in the right direction! Praise him, give him lots of love and treats. He will soon learn that he HAS to follow you, and look at how much fun it is! He is four months old. Don't expect him to walk perfectly on his lead. He has no idea how to walk on a leash at this point. He is following you when you are outside the home. The home is his safety blanket, and when you two are out and about, his safety blanket becomes you which is why he follows you while at the park.

Please be careful with dog parks. Dog parks are full of disease. He is just a baby, I hope all his shots are completed. If you have to carry him to the park for the time being, that is perfectly fine. Remember, he is just a baby.