The four competitive swimming strokes are freestyle, backstroke, breaststroke and butterfly. The combination of all four strokes is called individual medley. In freestyle, the stroke is characterized by the alternate stroking of the arms over the surface of the water and an alternating (up-and-down) flutter kick. Swimmers do a flip turn between laps. Backstroke consists of an alternating motion of the arms with a flutter kick while on the back. On turns, swimmers may rotate to the stomach and perform a flip turn and some part of the swimmer must touch the wall. The swimmer must finish on the back. The breaststroke requires simultaneous movements of the arms on the same horizontal plane. The hands are pressed out from in front of the breast in a heart shaped pattern and recovered under or on the surface of the water. The kick is a simultaneous somewhat circular motion similar to the action of a frog. On turns and at the finish, the swimmer must touch the wall with both hands simultaneously. A flip turn is not performed. Butterfly features a simultaneous recovery of the arms over the water combined with an undulating dolphin kick. In the kick, the swimmer must keep both legs together and may not flutter or use the breaststroke kick. Both hands must touch the wall simultaneously on the turns and the finish. A flip turn is not performed. The individual medley, commonly referred to as the I.M., features all four strokes. In the IM, the swimmer begins with the butterfly, then changes after one-fourth of the race to backstroke, then breaststroke and finally freestyle.