THE REFORMER IS A PIECE of resistance exercise equipment designed by Joseph Pilates. It consists of a platform that moves back and forth along a carriage. Resistance is provided by the exerciser's body weight and by springs attached to the carriage and platform. Despite the somewhat medieval name, the Pilates reformer is actually an amazingly elegant machine. The reformer provides finely tuned exercise resistance that allows one to work very precisely to develop good alignment, balance, core strength and flexibility.