 It was this improper flexion that ruined the reputation of their inventor, William Cavendish, 1st Duke of Newcastle-upon-Tyne.That being said, competent riders who correctly and tactfully use the draw and running reins can have success in correcting specific problems in horses that require retraining to get rid of bad habits.These are often the riders who use the equipment the least, because they can achieve correct results through good riding instead of gadgets.