There are loads of different styles of harnesses out there, but it’s been demonstrated that certain styles can actually cause damage to a dog’s shoulders and neck by placing pressure on these areas when the harness is being pulled on in whatever context. The best option for your dog’s comfort and safety is the style pictured above, which focuses any pressure onto the chest, and avoids pressing on those fragile areas of the throat and shoulder joints. A harness is a good choice in many situations, as it takes additional strain off the neck by not using the collar, and provides an additional grab-point for you should you need one. If you’re going to be using a long training line at all, you definitely need to pair it with a harness, as otherwise you risk sudden jolts to the neck which could cause serious discomfort or even injury.