The use of harnesses is relatively new and initially presented as ‘safer’ for the dog’s neck. Think. Do you know any dog that sustained a neck injury from a leash? No, you don’t. Training a dog to heel is one of the most important inputs toward training and using a collar is ‘exceedingly’ more effective than a harness. Fact. Dogs have been trained with collars for hundreds (thousands?) of years and never a peep about ‘neck injuries’ being a measurable hazard.