Butterfly Stroke

The butterfly, (fly for short) is a swimming stroke swum on the breast, with both arms moving simultaneously. The butterfly kick was developed separately, and is also known as the "dolphin kick". While other styles like the breaststroke, front crawl, or backstroke can be swum easily even by beginners, the butterfly requires very good technique to be feasible. Many students consider it the most difficult style. It is the newest swimming style swum in competition, first swum around 1934.

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.

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 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 body center and downward. The semicircle ends in front of the chin, with the hands close together so the swimmer can form a triangle with the fingers.
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 slightly higher than the hands and shoulders. The arms have to be swung forward fast in order to bring them to the front over the water. 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. 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 loses movement in the next pull phase, and a smaller entry, where the hands touch, wastes energy. After a brief rest the cycle repeats with the pull phase.

Leg Movement

The leg movement is similar to the leg movement in the front crawl, except the legs are synchronized with each other. 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 fuse 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.

Breathing

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.

Experienced swimmers continue looking toward the bottom of the pool while they inhale to keep the body balanced and in a straight line. 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, most notably Denis Pankratov, breathe to the side as in the front crawl, but their timing is otherwise the same. Such a style of breathing is quite uncommon though and generally discouraged by coaches.

Normally, a breath is taken every other stroke. This can be sustained over long distances. Oftentimes, 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 breath 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 the 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).

Body Movement

Swimming the arms or the legs separately is difficult, and correct body movement is great 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 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.


Start

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 economical. Rules allow for 15 m of underwater swimming, before the head must break the surface, and regular swimming begins.


Turn and Finish

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.

The Risks of Swimming

Swimming is generally a healthy activity and enjoys a low risk of injury compared with many other sports. Nevertheless there are some health risks with swimming, including the following:


Drowning, inhalation arising from


Adverse water conditions swamping or overwhelming the swimmer or causing water inhalation.
Actions of others pushing under water accidentally in play or intentionally.

Exhaustion or unconsciousness.

Incapacitation through shallow water blackout, heart attacks, carotid sinus syncope or stroke.


Adverse effects of immersion

Secondary drowning, where inhaled salt water creates a foam in the lungs that restricts breathing.

Salt water aspiration syndrome, SWAS.

Thermal shock after jumping into water can cause the heart to stop.

Exostosis which is an abnormal growth in the ear canal due to the frequent, long-term splashing of water into the ear canal. (Known as Surfers' ear or Swimmers' ear)


Exposure to chemicals

Disinfectant Chlorine will increase the pH of the water, if uncorrected the raised pH may cause eye or skin irritations.

Chlorine inhalation; breathing small quantities of chlorine gas from the water surface whilst swimming for long periods of time may have an adverse effect on the lungs, particularly for asthmatics. This problem may be resolved by using a pool with better ventilation, with an outdoor pool having the best results.

Chlorine also has a negative cosmetic effect after repeated long exposure, turning blonde hair green and stripping brown hair of all color, turning it very light blonde. Chlorine damages the structure of hair, turning it "frizzy."

Chlorine will often remain on skin in an anhydrous form, even after several washings. The Chlorine becomes odourous once it is back in an aqueous solution (when salivated on, during a shower, etc.)


Infection

Water is an excellent environment for many bacteria, parasites, fungi and viruses affecting humans depending on water quality.

Skin infections from both swimming and shower rooms can cause athlete's foot (boat bug). The easiest way to avoid this is to dry the space between the toes.

Microscopic parasites such as Cryptosporidium can be resistant to chlorine and can cause diarrheal illness when swimmers swallow pool water.

Ear infections, otitis media, (otitis externa).

Unfortunately, when chlorine levels are improperly balanced, severe health problems may result, such as chronic bronchitis and asthma.


Swimmer's own actions

Overuse injury; competitive butterfly stroke swimmers for example may develop some back pain, including vertebral fractures in rare cases, and shoulder pain after long years of training, breaststroke swimmers may develop knee pain, and hip pain, and freestyle and backstroke swimmers may develop shoulder pain, commonly referred to as swimmer's shoulder (a form of tendinitis).

Hyperventilation in a bid to extend underwater breath-hold times lowers blood carbon dioxide resulting in suppression of the urge to breathe and consequent loss of consciousness towards the end of the dive, see shallow water blackout for the mechanism.


Adverse water and weather conditions

Currents, including tides and rivers can cause exhaustion, move swimmers away from safety, or pull swimmers under water.

Wind enhances waves and can blow a swimmer off course.

Hypothermia, due to cold water, can cause rapid exhaustion and unconsciousness.

Sunburn severity can be increased by reflections in the water and the lack of clothing worn during swimming. Long-term exposure to the sun contributes to risk of skin cancer.


Objects in the water.

Propeller damage is a major cause of accidents, either by being run over by a boat or entanglement on climbing into a boat.

Collision with another swimmer, the pool walls, rocks or boats.

Diving into a submerged object, or the bottom, often in turbid water.

Snagging on underwater objects, particularly submerged branches or wrecks.

Stepping on sharp objects such as broken glass.


Dangerous aquatic life

Stings, jellyfish and some corals.

Piercings, sea urchins, zebra mussels, stingrays

Bites, sharks and other fish, snakes, lobster or crabs.

Electrocution, electric rays, electric eels.

Swimming Lessons

Children are often given formal swimming lessons, which serve to develop swimming technique and confidence. Children generally do not swim independently until 4 years of age.

In Sweden, Denmark, Norway and Finland, the curriculum for the fifth grade states that all children should learn how to swim as well as how to handle emergencies near water. Most commonly, children are expected to be able to swim 200 metres (220 yards) – of which at least 50 metres (55 yards) on their back – after first falling into deep water and getting their head under water. Even though about 95 percent of Swedish school children know how to swim, drowning remains the third most common cause of death among children.

In both the Netherlands and Belgium swimming lessons under school time (schoolzwemmen, school swimming) are supported by the government. Most schools provide swimming lessons. There is a long tradition of swimming lessons in the Netherlands, the Dutch translation for the breaststroke swimming style is even schoolslag (school style).

In many places, swimming lessons are provided by local swimming pools, both those run by the local authority and by private leisure companies. Many schools also include swimming lessons into their Physical Education curricula, provided either in the schools' own pool, or in the nearest public pool.

In the UK, the "Top-ups scheme" calls for school children who cannot swim by the age of 11 to receive intensive daily lessons. These children who have not reached Great Britain's National Curriculum standard of swimming 25 metres by the time they leave primary school will be given a half-hour lesson every day for two weeks during term-time.

In Canada and Mexico there has been a call for swimming to be included in the public school curriculum.

Swimming for exercise

Swimming is an excellent form of exercise. Because the density of the human body is approximately similar to that of water, the body is supported by the water and less stress is therefore placed on joints and bones. Therefore, swimming is frequently used as an exercise in rehabilitation after injuries or for those with disabilities.

Resistance swimming is one form of swimming exercise. It is done either for training purposes, to hold the swimmer in place for stroke analysis, or to enable swimming in a confined space for athletic or therapeutic reasons. Resistance swimming can be done either against a stream of moving water (often termed a swimming machine) or by holding the swimmer stationary with elastic attachments.

Swimming is primarily an aerobic exercise due to the long exercise time, requiring a constant oxygen supply to the muscles, except for short sprints where the muscles work anaerobically. As with most aerobic exercise it is believed to reduce the harmful effects of stress.

Occupational swimming

Some occupations require the workers to swim. For example, abalone divers or pearl divers swim and dive to obtain an economic benefit, as do spear fishermen.
Swimming is used to rescue other swimmers in distress. There are a number of specialized swimming styles specially for rescue purposes (see List of swimming styles). Such techniques are studied by lifeguards or members of the Coast Guard. The training of these techniques has also evolved into competitions such as surf lifesaving.
Swimming is also used in marine biology to observe plants and animals in their natural habitat. Other sciences use swimming, for example Konrad Lorenz swam with geese as part of his studies of animal behavior.

Swimming also has military purposes. A swimmer in the water or under the water can be difficult to detect, especially at night. Military swimming is usually done by special forces, such as Navy SEALS. Swimming is used to approach a location, gather intelligence, sabotage or combat, and to depart a location. This may also include airborne insertion into water or leaving a submerged submarine through a hatch or the torpedo tubes.
Swimming has become a professional sport as well. Companies such as Speedo and Tyr Sports, Inc. sponsor swimmers just as Nike sponsors basketball players (Nike also sponsors swimmers). Cash awards are also given at many of the major competitions for breaking records.

Competitive swimming

The goal of competitive swimming is to be the fastest to swim a given distance. Competitive swimming became popular in the nineteenth century, and currently comprises 34 events - 17 male events and 17 female events. Swimming is a popular event at the Summer Olympic Games, where male and female athletes compete in 13 of the recognized events each. Olympic events are held in a 50 meter pool. Competitive swimming's international governing body is FINA (Fédération Internationale de Natation), the International Swimming Federation.

The four competitive strokes are the butterfly, backstroke, breaststroke, and freestyle (frontcrawl). Also, there are different times to get to different levels in these strokes. These strokes can be swum individually or together in an individual medley (IM). The IM order is: 1) butterfly, 2) backstroke, 3) breaststroke, and 4) freestyle. There are two types of relays: medley and freestyle. The medley relay order is: 1) backstroke, 2) breaststroke, 3) butterfly, and 4) freestyle. Each of the four swimmers in the relay swims a predetermined distance, dependent on the overall length of the relay. The three relay lengths are 200 meters or yards, 400 meters or yards, and 800 meters or yards (which is only swum freestyle). In a 50 meter pool, each swimmer swims one length for the 200 relay, two lengths for the 400 relay, and four lengths for the 800 relay. In a 25 meter or yard pool, each swimmer swims two lengths for the 200 relay, four lengths for the 400 relay, and eight lengths for the 800 relay. Many full-size competition pools in the United States have a length of 50 meters and a width of 25 yards, allowing both short course (25 m or 25 yd pool) and long course (50 m pool) races to be held.
There are a few types of judges: a starter sets off the swimmers; turn judges check that the swimmers' turns are within rules; swim judges check the swimmers' strokes; time keepers time the swims; and the referee checks that everything is running smoothly. If an official catches a swimmer breaking a rule concerning the stroke he or she is swimming, that swimmer is said to be disqualified (commonly referred to as "DQ'd" or "deaked") and the swim is not considered valid.

In the United States and the United Kingdom communities may sponsor competitive swimming leagues for children and teenagers, made up of swim teams. These leagues for the most part adhere to recognized swimming rules, swim the standard strokes, but swim shorter lengths as events in swim meets. These leagues are usually active in the warmer months, and are not directly associated with a national or world swim organization. However, swimmers who begin their competitive swimming experience on such a local swim team may go on to join a nationally-governed team.

In Australia such competition is usually conducted under the auspices of a club affiliated with the State Association which in turn is affiliated with Swimming Australia, the FINA accredited body. This provides a direct pathway to top level competition for those capable of taking it while still providing a more relaxed environment for those whose main intent is to have fun swimming competitively.

Technique

The human body is composed primarily of water, and it has a very similar density to water. Roughly 70% of the body is water; while the lungs are filled with the air, the body is slightly less dense than the surrounding water, and there is a net upward force on the body. Thus staying afloat requires only a slight propelling of water downward relative to the body, and transverse motion only a slight propelling of water in a direction opposite to the direction of intended motion. This propelling is accomplished by using the hands and forearms as paddles, and by kicking the legs and feet to push water away from the body (though kicking accounts for relatively little overall). Since salt water (e.g., the ocean) is denser than fresh water (e.g., most swimming pools), less effort is required to stay afloat in salt water than in fresh water.

A number of swimming styles have been developed based on the implementation of some or all of the following principles:The torso and the legs should be kept as parallel as possible to the surface of the water. Dropped legs or a slanted torso dramatically increase drag. The hand should be extended forward of the head as much as possible. This increases the average length at the water-line, substantially increasing speed.

Recent research has shown that hand force applied to the water is really generated by the rotation of the hips, and not by the muscles of the arm. The muscles that pull the arm through the water are attached within one inch of the top of the arm. With a 21" arm, the lever ratio is 1:20, which means that a 100 lbs. of pull by the shoulder muscles produces only 5 lbs. of force at the hand as it pushes back against the water. The torque generated by the larger, stronger hip muscles, on the other hand, whips the hands through the water, much like golfers or batters whip their clubs and bats through the air with a fast turn of the hips. Elite swimmers who were able to make modest increases in the acceleration of their hips doubled their peak hand force output.

The time spent on the side should be maximized so the shoulders do not break the water-line and do not produce bow waves. This reduces the frontal cross-section, reducing drag further, and also increasing the ratio between the body's water-line-length and width. Similar improvements are possible by orienting the narrowest direction of head, hands, legs and arms into the water. The torso is by far the most critical. The motion of the hand, arm, and leg from the back to the front should be in the air for as much time during the recovery stroke as possible, and in the water, oriented as hydrodynamically as possible, because the returning appendage has to move at least twice as fast as the swimmer, and in the water generates eight times the drag (which increases with the cube of the speed) of an equal amount of torso frontal area. Rotating your shoulders also adds power to one's pull by using abdominal muscles to help pull the arm through the water.

The basic "catch" of the water is not nearly as critical as the above items. Most swimmers simply grab water with their hand flat, or the fingers slightly spread, and then draw it smoothly down their body. None of the above techniques require improved strength. With strength training, the hands and feet can be extended further into the water, gaining more propulsion. For beginners, increased strength brings only small improvements if the above strategies (minimising drag and lengthening water-line) are not optimal.

Another technique that can help an athlete swim at a higher performance level is proper breathing techniques. Breathing correctly can make you swim faster and make it harder for you to be fatigued. Competitive swimmers take in one breath and gradually let it out over three to four strokes. As the race progresses and the swimmer becomes tired, less oxygen from those breaths reach his muscles. You can practice and teach your body how to run on less than normal levels of oxygen. Take a deep breath at one side of a pool, submerge yourself fully, and kick like a dolphin. Try to simulate a torpedo. Try crossing the pool with one breath, and once you can do that extend the distance. Another way you can practice endurance is by taking a breath and letting it out over six strokes (while freestyle swimming).

Skeletal animation and computational fluid dynamics allow simulation of swimmers. This allows to quantify forces on joints and muscles, and, if multiple simulations are employed, to compare different styles or individuals. By means of computer graphics or motion capture the simulation can be compared to real swimmers. While this removes many doubts, it is still guess work needed to create new styles, it is a didactic challenge to formulate a manual for swimmers, and the feel of the water is still needed to close a control loop so that the swimming styles does not drift away afterwards