If this is a problem, talk to a trainer or dog obedience school about using a head halter called the Gentle Leader. It's a wonderful device that keeps them from pulling so hard. Many dog lovers like retractable leads, but Kian doesn't favor them because they tend to reduce the owner's control. It doesn't give you time to prevent a dangerous situation from developing. If you want to run with your dog, Kian says, first be sure it's suited to such exercise.
Many dogs are mixed breeds, which are a great thing.
Yet if you have a scent hound like a bloodhound, they're so into smelling everything they want to stop every few feet and not run with you. And if you have a tiny dog like a dachshund, there's no way it's going to keep up with you for very long. And be sure to have plenty of water with you. There are lots of neat devices out there, like collapsible dishes, in pet supply stores and catalogs. I take a squirt bottle, and my dogs have learned to lick water out of that.