The main difference between a martingale collar and a regular collar is that it tightens up as a dog pulls. The purpose of this is not to choke a dog, but to prevent a dog from escape the collar. Many dogs have heads that are the same size or smaller than its neck. With a regular collar, when a dog backs up from up, it may be able to slip a regular collar. With a martingale collar, when this happens, the collar tightens and prevents it from come up over a dog's head.