They sound like a good idea. The act of allowing your dog a measure of freedom while retaining some measure of control. The problem with an extendable lead is that you’re never really in control. Extendable leads are usually just cheap plastic shells housing a spring loaded length of thin cord. They aren’t as strong as normal leads and over time they almost always break, but the real reasons never to use them are listed below.

1. Extendable Leads can cause serious neck and spinal injuries. If your dog takes off suddenly or at speed then when they reach the end of their lead they risk suffering severe whiplash and other related injuries. Hundreds of dogs are crippled every year because of these cruel devices. If you need to have your dog on a lead then use a proper strong lead 6 feet long or less.

2. You are not in control of a dog if they are 10 or twenty feet away from you. This additional distance can enable them to get into situations like traffic or confrontations with other animals.

3. By using an extendable lead you run the risk of rope burns. Many people suffer burns as a result of trying to prevent their dog from pulling. A big dog will easily be able to overpower the flimsy mechanisms inside one of these leads and the only option left to you will be to try and hold on to the cord itself. These injuries can be very painful and in some extreme conditions have lead to amputations.

4. Dogs can be spooked by the internal workings of extending leads. If you ever drop the lead with the catch off, the lead will begin to retract. If your dog is in any way skittish then the prospect of being chased by a whirring lump of plastic that they cannot escape is pretty much their worst nightmare.

5. Extendable leads are teaching your dog to pull. Dogs are smart problem solving creatures and they quickly learn that with extending leads they can can gain ground by pulling hard. This will teach your dog that if they pull they can be rewarded with extra freedom, which can make walking your dog a less pleasurable experience.