The Reformer consists of a carriage that moves back and forth along tracks within a wooden frame (similar to a bed frame). Springs of varying strength are attached to both the carriage and the platform to provide resistance during a variety of exercises done on the device. The principle is, as so often, a movable base and progressive, i.e. increasing, resistance: Pilates always uses spring resistance, not weights. A complete whole-body workout (feet, calves, thighs, hips, abdomen, back, arms and shoulders) can be performed on the Reformer.