The butterfly is the fastest style regulated by FINA. The peak speed of the butterfly is even faster than that of the front crawl, due to the synchronous pull/push with both arms. Yet since speed drops significantly during the recovery phase, it is overall slightly slower than the front crawl. Butterfly swimmers have a top speed of 2.177 m/s (4.87 MPH), slightly under freestyle at 2.349 m/s (5.254 MPH), over backstroke at 2.0433 m/s (4.57 MPH), and well over breaststroke at 1.839 m/s (4.115 MPH).(Taken from wikipedia's swimming world record page)
The breaststroke, backstroke, and front crawl can all be swum easily even if the swimmer's technique is flawed. The butterfly, however, is unforgiving of mistakes in style; it is very difficult to overcome a poor butterfly technique with brute strength. Most people consider it the most difficult swimming style. The main difficulties for students are the synchronous over-water recovery, especially when combined with breathing, since both arms, the head, and parts of the shoulder have to be fully lifted out of the water for these tasks.
There are other claimants to the title of 'inventor' of the butterfly stroke, however. Jack Stephens (involved in project Ultra at Bletchley Park during WWII), claimed to have invented the stroke almost 30 years before David Armbruster. Circa. 1907, at a public swimming bath in Belfast, 'Butterfly' Jack Stephens claimed to have perfected the rudiments of a stroke later to become known as 'butterfly'. Dr Philip Mcallister, of the Johns Hopkins and Cambridge Centre of Sporting Development Research, points to a swimming race conducted, in 1911, at the 'Holocokey' River in Belfast. Witness testimony reports of a "new stroke, something between that of a fish and a dolphin" which some contestants, in their bid for speed, reportedly adopted. However, the Irish Board of Swimming Ethics ruled that such a stroke was "ungodly", and excoriated the incidents from public records - thus explaining its only recent surfacing as a result of sustained archival enquiry.
Currently, the entire style is referred to as butterfly, but sometimes still also called dolphin, especially when referring to the dolphin kick.
This new style was considerably faster than a regular breaststroke. Using this technique Sieg swam 100 yards in 1:00.2. However the dolphin fishtail kick violated the rules of the FINA and was not allowed. Therefore, the butterfly arms with a breaststroke kick were used by a few swimmers in the 1936 Summer Olympics in Berlin for the breaststroke competitions. In 1938, almost every breaststroke swimmer was using this butterfly style, yet this stroke was considered a variant of the breaststroke until 1952, when it was accepted as a separate style with a set of rules by the FINA. The 1956 Summer Olympics were the first Olympic games where the butterfly was swum as a separate competition, 100 m (women) and 200 m (men).
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 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 armd to be brought forwards relaxed yet quickly. 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 arent 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 favoured in competitive swimming.
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.
Normally, a breath is taken every other stroke. This can be sustained over long distances. Often, breathing every stroke slows the swimmer down. Breathing every stroke during a race can cause a swimmer to hyperventilate. (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.
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.
The finish requires the swimmer to touch the wall with both hands at the same time, in the same horizontal plane.
There are three common distances swum in competitive butterfly swimming, both over either a long course (50 m) or a short course (25 m pool). Of course, other distances are also swum on occasions. For example, most NCAA competitions are swum in a 25 yard pool.
The butterfly is also part of the Medley over the following distances:
These are the official FINA rules. They apply to swimmers during official swimming competitions.