A leash assembly includes a body with a handle and a cord which has an end captive in the body. The assembly is adjustable whereby the tension in the cord can be caused automatically to increase and decrease respectively causing a shudder in the cord. Optionally, a noise my accompany the change in tension in the cord. The leash will be attached in use to a collar or harness worn, for example, by a dog and the shudder is used to assist in training the animal.