The butterfly technique with the dolphin kick consists of synchronous arm movement with a synchronous leg kick. Good technique is crucial to swim this style effectively. The wave-like body movement is also very significant, as this is the key to easy synchronous over-water recovery and breathing.
In the initial position, the swimmer lies on the breast, the arms are stretched to the front, and the legs are extended to the back.
The butterfly stroke has three major parts, the pull, the push, and the recovery. These can also be further subdivided. From the initial position, the arm movement starts very similarly to the breast stroke. At the beginning the hands sink a little bit down with the palms facing outwards and slightly down at shoulder width, then the hands move out to create a Y. This is called catching the water. The pull movement follows a semicircle with the elbow higher than the hand and the hand pointing towards the center of the body and downward. Do not form the traditionally taught "keyhole" when using this stroke, as it disrupts the flow and speed of the stroke. The arms should be pushed straight back after the Y is formed.
The push pushes the palm backward through the water underneath the body at the beginning and at the side of the body at the end of the push. The swimmer only pushes the arms 1/3 of the way to the hips, making it easier to enter into the recover and making the recovery shorter and making the breathing window shorter. The movement increases speed throughout the pull/push phase until the hand is the fastest at the end of the push. This step is called the release and is crucial for the recovery. The speed at the end of the push is used to help with the recovery.
The recovery swings the arms sideways across the water surface to the front, with the elbows straight. The arms should be swung forward from the end of the underwater movement, the extension of the tricep in combination with the butterfly kick will allow the arm to be brought forwards relaxed yet quickly. In contrast to the front crawl recovery, this arm recovery is a ballistic shot. The only other way of lifting the arms and the shoulders out of the water is by dropping one's hip. Therefore the recovery, at least the acceleration of the arms, is in no way relaxed. It is important not to enter the water too early, because this would generate extra resistance as the arms moved forward in the water against the swimming direction, however, during longer distances, this cannot be avoided, and it should be noted that it is more important to avoid dropping one's hips. A high elbow recovery, as in front crawl, would be disadvantageous because of the natural undulations that are partially caused by the recovery and the relaxed movement caused by the momentum of a tricep extension. Limitations of the shoulder movement in the human body make such a motion unlikely.
The arms enter the water with the thumbs first at shoulder width. A wider entry loses movement in the next pull phase, and a smaller entry, where the hands touch, wastes energy. The cycle repeats with the pull phase. However, some people prefer to touch in front, because it helps them catch water, as long as they can do this efficiently, they are not losing anything. The underwater part is actually more like a keyhole than it isn't, contrary to what was said in the 1st paragraph.
Generally, viewed from below, the arm movement forms a fat "keyhole" figure during the stroke cycle in the water. However, more recently, a straighter arm pull has been favored in competitive swimming.
The leg movement is similar to the leg movement in the front crawl, except the legs are synchronized with each other, and it uses a wholly different set of muscles. The shoulders are brought above the surface by a strong up and medium down kick, and back below the surface by a strong down and medium up kick. A smooth undulation fuses the motion together.
The feet are pressed together to avoid loss of water-pressure. The feet are naturally pointing downwards, giving downwards thrust, moving up the feet and pressing down the head.
There is no actual stipulation in competitive butterfly rules that a swimmer make a fixed number of pulses in butterfly–the swimmer may kick as little or as much as he or she may wish. While competitive rules allow such a choice, the typical method of swimming butterfly is with two kicks.
As butterfly originated as a variant on breaststroke, it would be performed with a breaststroke or whip kick by some swimmers. While breaststroke was separated from butterfly in 1953, the breaststroke kick in butterfly was not officially outlawed until 2001. However a number of Masters swimmers were upset with the change since they came from a time when butterfly was usually swum with a breaststroke kick. FINA was then convinced to allow a breaststroke kick in Masters swimming. Given the option, most swimmers choose to use a dolphin kicking action, but there still is a small minority of swimmers who prefer the breaststroke kick, for recreational swimming and even for competition.
There is only a short window for breathing in the butterfly. If this window is missed, swimming becomes very difficult. Optimally, a butterfly swimmer synchronizes the taking of breaths with the undulation of the body to simplify the breathing process; doing this well requires some attention to butterfly stroke technique. The breathing process begins during the underwater "press" portion of the stroke. As the hands and forearms move underneath the chest, the body will naturally rise toward the surface of the water. With a minimum of effort, the swimmer can lift the head to break the surface fully. The swimmer breathes in through the mouth. The head goes back in the water after the arms come out of the water as they are swinging forward over the surface of the water. If the head stays out too long, the recovery is hindered. The swimmer breathes out through mouth and nose till the next breath. Some swimmers breathe to the side as in the front crawl, but their timing is otherwise the same.
Normally, a breath is taken every other stroke. This can be sustained over long distances. Often, breathing every stroke slows the swimmer down. (At a certain level, the stroke with a breath and the stroke without a breath become synonymous in their speed; therefore, very experienced competitors - such as Michael Phelps - may breathe every stroke.) Other intervals of breathing practiced by elite swimmers include the "two up, one down" approach in which the swimmer breathes for two successive strokes and then keeps their head in the water on the next stroke, which is easier on the lungs. Swimmers with good lung capacity might also breathe every 3rd stroke during sprints or the finish. Some swimmers can even hold their breaths for an entire race (assuming that it is a short one).
Swimming butterfly is difficult if the core is not utilized, and correct timing and body movement makes swimming the butterfly much easier. The body moves in a wave-like fashion, controlled by the core, and as the chest is pressed down, the hips go up, and the posterior breaks the water surface and transfers into a fluid kick. During the push phase the chest goes up and the hips are at their lowest position. In this style, the second pulse in the cycle is stronger than the first pulse, as the second pulse is more in flow with the body movement.
Although butterfly is very compatible with diving, the resulting reduction in wave drag does not lead to an overall reduction of drag. In the modern style of the Butterfly stroke one does only little vertical movement of the body.
Butterfly uses the regular start for swimming. After the start a sliding phase follows under water, followed by dolphin kicks swam under water. Swimming under water reduces the drag from breaking the surface and is very economical. Rules allow for 15 m of underwater swimming, before the head must break the surface, and regular swimming begins.
During turns and during the finish, both hands must simultaneously touch the wall while the swimmer remains swimming face down. The swimmer touches the wall with both hands while bending the elbows slightly. The bent elbows allow the swimmer to push himself or herself away from the wall and turn sideways. One hand leaves the wall to be moved to the front underwater. At the same time the legs are pulled closer and moved underneath of the body towards the wall. The second hand leaves the wall to be moved to the front over water. It is commonly referred to as an "over/under turn" or an "open turn." The legs touch the wall and the hands are at the front. The swimmer sinks under water and lays on the breast, or nearly so. Then the swimmer pushes off the wall, keeping a streamline position with the hands to the front. Similar to the start, the swimmer is allowed to swim 15m underwater before the head must break the surface. Most swimmers dolphin kick after an initial gliding phase.
The finish requires the swimmer to touch the wall with both hands at the same time, in the same horizontal plane.