Choke chains have been around for many years. They are so common that very few people will give them a second thought.
Often referred to as check collars, some trainers will use them as a quick correction collar. These were never meant to be used for walking a dog.
Apart from being ineffective as a training aid they have been responsible for many medical conditions including
Injured ocular blood vessels
Tracheal and esophageal damage
Severe neck sprain
Laryngeal nerve paralysis
Transient forelegs paralysis
Permanent nerve damage
Recurring pain in the eyes
A study conducted In German involved 50 dogs using Choke chains. These dogs were followed their entire lives until death. Autopsies were performed. 48 of the dogs had some form of neck, back, trachea injury. two were genetic while 46 were caused by trauma.
It's often advocated that Choke chains are used on dogs from a young age. Using these on a young animal is extremely likely to result in much more severe long term injury.
The principle of the Choke chain is to cause and inflict sufficient pain in order that the dog will learn that to disobey will cause pain and discomfort. So far from preventing pain and injury, the primary purpose is to cause it. Using Choke chains once you have inflicted sufficient pain, your dog will learn to respond to the clinking sound of the chain, this may be well and true, but these dogs in general will be flinching, cowering or frightened in anticipation of the pain that usually will follow.
All too often dogs are damaging themselves by pulling with all their weight and strength. That is a lot of pressure on the neck.
Dogs are usually very quick to learn with the correct techniques and handling.
Inflicting pain should never be justified. If you are having problems with training your dog, then there are many pain free technique trainers available.
Over the years I have trained many by simply stopping moving, standing still, Do not talk or make any sounds, once your dog stops pulling or stands beside you or relatively still you can move again. You're not stopping for a chin wag or meeting with the dog. Stop still and ignore until the dog is ready to move again. You may have to repeat this several times . Some maybe over and over again. You may look a bit silly on your stop and start walk, but not as silly as someone choking their pet to death.
Finding a treat & reward system may be another method. All too often people are shouting and screaming at the dogs, this should not be necessary, as the dog has no idea what you are on about anyway and this won't help in future as you will have to continue to shout and scream so your dog understands.
There are thousands of trainers that can show you more effective ways than the Choke chain or involving force and deliberating injury.