“I do not believe that there is a harness on the market that is nonrestrictive and that also helps the dog not to pull,” says Dr. Zink.” There are however some very nice, well constructed, nonrestrictive harnesses on the market. However, those should not be considered as a method to teach a dog not to pull. In my opinion the real way to get a dog to stop pulling is to train it.”
It isn't all harnesses, just the ones that are designed to inhibit the dog's pulling. I know my harness that I use to bike with is fine, it's got the D ring on the back, and my dog has complete freedom in it. I'd like the strap under his chest to be a tad longer, but then he'd be able to get out of it.