We get people in the store all the time that are looking for a harness for their dog. Unfortunately, most of the time, they aren't actually looking for a harness, but for a way to control a dogs pulling when on leash, and a standard harness is just about the opposite of what they need.
Harnesses are designed, generally, to restrain an animal. To prevent "Houdini" dogs from slipping out of its collar when on tether, or to protect it when driving in a vehicle. Harnesses, such as H-type, mesh, and figure 8, spread the pulling tension over a larger area than a collar, so that the dog doesn't choke itself with its pulling. This allows the dog to actually pull harder without hurting itself! Exactly the opposite of what most people think the harness will do.
Harnesses designed for use in the car have extra padding and to lessen the impact on the dog in case of collision. The also have stronger attachment points, to prevent it from becoming a projectile that can actually harm the vehicle's occupants. These can also be used for walking, but again, they will allow a dog to exert more pressure without discomfort, which can make them harder to control.
When a pet owner is looking for help in controlling a dog while walking, there are many options. The best of which is training. There are classes available for dogs and owners to learn to walk on leash properly, as well as many online resources. Investing time and effort can really pay off with most dogs.
When training isn't the answer, either because of the time investment or the dog not wanting to learn, there are products that can be very effective. Control collars, control harnesses and head collars just to name a few.
A control collar will use a physical deterrent to stop the animal from pulling. Martingales are a combination of a nylon collar and a choke chain, making for the gentlest of the "choke" type correction devices. Choke chains can actually choke the dog, and used improperly can damage the dogs trachea if the dog really fights it. They can be effective if only a light control is needed. Pinch chokes add a set of barbs or points that dig in when the dog pulls, making them more uncomfortable to pull against and therefore more effective in strong pullers. But again, used improperly they can hurt the animal.
Control harnesses will work like a harness in normal use, but when the dog pulls, they will apply an unusual pressure that is uncomfortable and encourages the dog not to continue pulling. These passive devices can be very effective in the right situation, and should not harm the animal if used as directed.
Head collars come in a variety of models, some pull under the chin, some behind the head, but in general, when the animal pulls, the harness restrains their head, giving the owner more control. These do require training with the dog to work properly, and not every dog will submit to them. They can look like muzzles, but they are not, and were not meant prevent biting.
Finding the proper answer for your dog's walking issues isn't difficult, with the proper equipment and advice. Don't wait until you need rotator cuff surgery to decide to fix the problem.