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Butterfly stroke

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Butterfly, or short fly, is swum on the breast, with the arms moving synchronously. The butterfly kick was developed separately, and is also known as Dolphin. While other styles like breaststroke, front crawl, or backstroke can be swum easily even for beginners, butterfly requires a very good technique to be feasible. Most students consider it the most difficult style. It is also the newest swimming style swum on competitions, first swum around 1934.

Speed and Ergonomics

Butterfly is the second fastest style after front crawl, and the fastest style regulated by FINA. The speed of top swimmers is around 1.67 m/s, very close to the speed of front crawl swimmers with 1.71 m/s, and significantly faster than backstroke (1.52 m/s) and breaststroke (1.37 m/s). The peak speed Butterfly is even faster than the peak speed of front crawl due to the synchronous pull/push with both arms, yet drops significantly during the recovery phase, making it overall slightly slower than front crawl.

Breaststroke, backstroke, and front crawl can be swum easily even if the technique is flawed. Butterfly, however, is unforgiving to mistakes in the style, and it is very difficult to overcome a bad butterfly style with brute strength. Most people consider it the most difficult style to swim, yet done correctly competitive butterfly swimming requires less energy than breaststroke. The main difficulties for students are the synchronous over water recovery, especially when combined with breathing, as both arms, the head, and parts of the shoulder have to be lifted out of the water for these tasks.


The butterfly style evolved from breaststroke. David Armbruster, swimming coach at the University of Iowa, researched breaststroke, especially considering the problem of the increased drag due to the underwater recovery. In 1934 Armbruster refined a method to bring the arms forward over water in breaststroke. He called this style butterfly. While butterfly was difficult, it brought a great improvement in speed. One year later, in 1935, Jack Sieg (Seig?), a swimmer also from the University of Iowa developed a kick technique involving swimming on his side and beating his legs in unison similar to a fish tail, and modified the technique afterward to swim it face down. He called this style Dolphin fishtail kick. Armbruster and Sieg quickly found out that combining these techniques created a very fast swimming style consisting of butterfly arms with two dolphin kicks per cycle. Nowadays, 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 regular breaststroke, and 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 were butterfly was swum as a separate competition, swum over 100m and 200m.

(see History of swimming)


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 for an 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 Arm Movement

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 similar to the front crawl. At the beginning the hands sink a little bit down with the palms facing outwards and slightly down at shoulder width. 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 body center and downward. The semicircle ends in front of the chest at the beginning of the ribcage.

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 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 slightly higher than the hands and shoulders. The arms have to be swung forward fast in order to bring them to the front over water and not to enter the water too early, generating extra resistance of the arms moving against the swimming direction in the water. A high elbow recovery as in front crawl would save more energy, yet the movement restrictions in the shoulders do not allow this easily, and due to the synchronized movement it is not possible to roll around the shoulders as in front crawl.

The arms enter the water with the thumbs first at shoulder width. A wider entry looses movement in the next pull phase, and a smaller entry were the hands touch wastes energy. After a brief rest the cycle repeats with the pull phase.

The Leg Movement

The leg movement is similar to the leg movement in front crawl, except they are synchronized and the entire body moves in a wave-like motion to assist the legs. The first kick comes when the hands enter the water and the second, stronger kick comes at the middle of the push phase. The second kick assists in the recovery of the arms.

Alternatively, it is possible to do only one kick per cycle, but this is not advisable as it will make the recovery more difficult. Also, it is possible to swim butterfly arms with a breaststroke kick, were the main push of the kick comes at the middle of the push phase. However, this is not allowed by the FINA, but sometimes done for training purposes. A breaststroke kick will be not as fast as the dolphin kick, but is also a feasible swimming style.


There is only a short window for breathing in butterfly. If this window is missed, the style becomes very difficult to swim. Normally the head is in the water. At the end of the push before the hands come out of the water, the head also comes out of the water by bending the head backwards. The swimmer breathes in through the mouth. The head goes back in the water again shortly after the arms come out 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.

Normally, a breath is taken every other cycle. This can be sustained over long distances. Breathing every cycle slows the swimmer down. Swimmers may also breathe every 3rd cycle or less during sprints or the finish, depending on the need for air.

Body Movement

Swimming the arms or the legs separately is difficult, and the body movement is crucial for the arms and legs to use their full potential. The body moves in a wave like fashion, controlled by the arm movement. As the hands go in, the hips go up, and the posterior breaks the water surface. During the push phase the head goes up and the hip are at the lowest position. In this style, the second kick in the cycle is stronger than the first kick, as the second kick 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 swum under water. Swimming under water reduces the drag from breaking the surface and is very economic. Rules allow for 15m of underwater swimming, before the head must break the surface, and regular swimming resumes.

Turn and Finish

During turns and during the finish, the hands must touch the wall at the same time on the breast. The swimmer touches the wall with both hands while bending the elbows slightly. The bent elbows allow the swimmer to push himself away from the wall and turning 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. 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. Next the swimmer pushes himself 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 swim a dolphin kick after a initial gliding phase.

The finish requires the swimmer to touch the wall with both hands at the same time.


There are three common distances swum in competitive butterfly swimming, both over either a long course (50m pool) or a short course (25m pool). Of course, other distances are also swum on occasions.

  • 50m Butterfly
  • 100m Butterfly
  • 200m Butterfly

Butterfly is also part of the Medley over the following distances:

  • 100m Medley (short 25m pool only)
  • 200m Medley
  • 400m Medley
  • 4*100m Medley

These are the official FINA rules. They apply to swimmers during official swimming competitions.

  • From the beginning of the first arm stroke after the start and each turn, the body shall be kept on the breast. Under water kicking on the side is allowed. It is not permitted to roll onto the back at any time.
  • Both arms shall be brought forward together over the water and brought backward simultaneously through-out the race, except after the start and at turns
  • All up and down movements of the legs must be simultaneous. The position of the legs or the feet need not be on the same level, but they shall not alternate in relation to each other. A breaststroke kicking movement is not permitted.
  • At each turn and at the finish of the race, the touch shall be made with both hands simultaneously, at, above or below the water surface.
  • At the start and at turns, a swimmer is permitted one or more leg kicks and one arm pull under the water, which must bring him to the surface. It shall be permissible for a swimmer to be completely submerged for a distance of not more than 15 meters after the start and after each turn. By that point, the head must have broken the surface. The swimmer must remain on the surface until the next turn or finish.

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