Science Fair Project Encyclopedia
Swimming is the method by which humans (or other animals) move themselves through water. Swimming is a popular recreational activity, particularly in hot countries and in areas with natural watercourses. Swimming is also a competitive sport. There are many health benefits of swimming, yet basic swimming skills and safety precautions are needed to participate in water activities.
The human body, being composed mostly of water, has nearly the same density as water. 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 motion, due to generally low hydrodynamic drag. This propelling is typically accomplished by cupping the hands and using them as paddles, and by kicking the legs to push water away from the body.
With practice, technique can convert a slow or average swimmer to at least a moderately fast swimmer. Since speed converts directly into distance, the same techniques that improve speed also aid one to move farther with the same effort.
The torso and the legs should be kept as much as possible parallel to the surface of the water. Drooped legs or a slanted torso dramatically increase drag.
Try to have a pointed hand above the head, pointed forward as much as possible. This increases the average length at the water-line, substantially increasing speed. This is an effect long used by boat designers, and unconsciously used by "naturally good swimmers."
Try to maximize the time spent on the side because the torso is smaller front-to-back than side-to-side on most swimmers. This reduces the frontal cross-section, reducing drag further, and also increasing the ratio between the bodies 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 back to the front should be in the air as much as possible, and in the water, oriented as perfectly 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 (drag increases with the cube of the speed) of an equal amount of torso frontal area.
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.
Note that 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 (minimise drag and lengthen water-line) are not optimal.
A number of swimming styles have been developed based on the implementation of some or all of these principles.
Main article: History of swimming
Swimming has been known since prehistoric times. Drawings from the stone age were found in "the cave of swimmers" near Wadi Sora (or Sura) in the southwestern part of Egypt. Written references date back up to 2000 B.C., including Gilgamesh, the Iliad, the Odyssey, the Bible (Ezekiel 47:5, Acts 27:42, Isaiah 25:11), Beowulf, and other sagas. In 1538 Nicolas Wynman, German professor of languages, wrote the first swimming book "Colymbetes". Competitive swimming in Europe started around 1800, mostly using breaststroke. The front crawl, then called the trudgen was introduced in 1873 by John Arthur Trudgen, copying it from Native Americans.
Swimming was part of the first modern Olympic games in 1896 in Athens. In 1902 the trudgen was improved by Richard Cavill, using the flutter kick. In 1908, the world swimming association Federation Internationale de Natation (FINA) was formed. Butterfly was first a variant of Breaststroke, until it was accepted as a separate style in 1952.
Competitive swimming is swimming with the goal to maximize performance, usually the speed of swimming. Competitive swimming became popular in the 19th century, and is an event at the Summer Olympic Games. The competitive swimming's governing body is FINA, and there are four swimming disciplines regulated by it, swum over different distances.
- Freestyle refers to "any style", and in competitive swimming places no restrictions on what action the competitors use, except during the freestyle portion of medley swimming. In practice, almost all freestyle events are swum using front crawl. Events are held at distances of 50 m, 100 m, 200 m, 400 m, 800 m and 1500 m. Events are held in yards at distances of 50 y, 100 y, 200 y, 500 y, 1000 y, and 1650 y.
- Butterfly events require that the swimmer's actions retain bilateral symmetry (the left side of the body has to do the same as the right). The butterfly is the most physically demanding of the four strokes. Events are held at distances of 50 m, 100 m, and 200 m. Events are also held in yards.
- Breaststroke, from which the butterfly stroke evolved, places the additional restriction that the swimmer's hands must be pushed forward together from the breast and that the elbows must remain under the water. It is the slowest stroke in competitive swimming. Events are held at distances of 50 m, 100 m, and 200 m. This stroke, as well as butterfly requires great shoulder strength. Events are also held in yards.
- Backstroke places no symmetry restrictions, but swimmers must lay on their back at all times except during turns to perform the stroke. Backstroke is performed, in essence, as an inversion of the crawl — competitors swing their arms back over their shoulder, alternately, and pull through under the water to provide motive power, with a flutter kick. Events are held at distances of 50 m, 100 m, and 200 m. Events are also held in yards.
In addition to that there are a number of combination events in competitive swimming.
- Relay, where a number of swimmers swim sequentially. Events are held at distances of 4×50 m freestyle (short 25 lane only), 4×100 m freestyle and 4×200 m freestyle.
- Individual Medley, where one swimmer swims Butterfly, Backstroke, Breaststroke, and Freestyle in this order. Events are held at distances of 100 m (short 25 m lane only), 200 m, and 400 m.
- Medley Relay, where four swimmer swim Backstroke, Breaststroke, Butterfly, and Freestyle in this order. Events are held at distances of 4×50 m medley (short 25 lane only) and 4×100 m medley.
Competitive swimming has traditionally been dominated by the United States, but recently that dominance has been challenged by Australia , where swimming is a hugely popular recreational activity, and participant and spectator sport. The success of Australian swimmers like Ian Thorpe, Grant Hackett, and Kieren Perkins is reminiscent of Australia's previous golden age of swimming in the 1950s and 1960s, which saw the emergence of swimmers such as Shane Gould and Dawn Fraser, but for the moment the American swimmers led by Michael Phelps, Colin Cordes, Natalie Coughlin, Kaitlin Sandeno, and Kara Lynn Joyce will be able to hold off the Australians just like they did in the 2004 Olympics.
There are also a number of other Competitive swimming performances, for example a long distance 5 kilometer open-water event, which became part of the Olympic program in 2000, or long distance swims across the English Channel, or circumnavigating Manhattan Island. The world record for the longest nonstop swim is held by Martin Strel for swimming 504km nonstop in 2001 in the Danube River. He also swam the Mississippi River in 2002 in 66+2days, a total of 3885km. The current holder of the most world records for long distance swimming is Vicki Keith.
The most common reason for swimming is probably recreation, where the swimmer enters the water merely for enjoyment. Many swimming styles are suitable for recreational swimming. Most recreational swimmers prefer a style that keeps their head out of the water and uses an underwater arm recovery, for example breaststroke, side stroke, or 'dog paddle', however, out-of-water recovery of freestyle or butterfly gives rise to better exploitation of the difference in viscosity of the two media (air and water). Butterfly, which consists of out-of-water recovery with even symmetry in body movements, is most suited to rough water swimming. For example, Vicky Keithy crossed the rough waters of Lake Ontario using butterfly. Much of recreational swimming takes place in pools, where the water is calm. Therefore freestyle (which does not work as well in rough water) is suitable. However, playing around in rough water is a common source of recreation, but is sometimes dangerous due to undertow or being smashed into rocks on the bottom of the lake. Swimming pools are popular venues for recreational swimming, as are beaches, lakes, swimming holes, creeks, rivers, and sometimes canals.
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 for example by lifeguards, or members of the Coast Guard. The training of these techniques also evolved into competitions, as for example surf lifesaving.
Swimming is also done for scientific research. Swimming is studied to improve the swimming performances of competitive swimmers. Swimming is also used in marine biology to observe plants and animals in their natural habitat. Other sciences may also use swimming. Konrad Lorenz for example swam with geese as part of his studies of animal behavior.
Swimming also has military purposes besides the mere need to cross waters. 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, as for example 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. Special equipment and techniques are also used to engage hostiles in and under water.
Swimming for exercise
Swimming is a good form of exercise. Because the density of the human body is approximately similar to water, the body is supported by the water and less stress is therefore placed on joints and bones. Furthermore, the resistance against movement depends heavily on the speed of the movement, allowing the fine tuning of the exercise according to ones ability. Therefore, swimming is frequently used as an exercise in rehabilitation after injuries or for the disabled.
Swimming is an aerobic exercise due to the relatively long exercise times, 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. While aerobic exercises usually burn fat and help with losing weight, this effect is limited in swimming, even though being in cold water burns more food energy to maintain body temperature.
The reason that swimming does not significantly reduce weight is still poorly understood, but seems to be related to the better heat conduction of water. A number of reasons are suspected.
- First, water cools the body much faster than air, and most researchers believe that subsequently the body aims to maintain a layer of fat under the skin for insulation.
- Secondly, it is believed that appetite decreases as your body temperature increases, as for example during exercise. However, during swimming the body is cooled down almost instantly as the surrounding water is usually cooler than the body temperature, and some researchers believe that this may actually increase the appetite. This assumption is not yet proven by research.
- Finally, some researchers also believe that the metabolism of the body increases at higher body temperature, burning more food energy. Again, during swimming the body is cooled down by the surrounding water, reducing the metabolism, and subsequently the amount of food energy burnt. This assumption is also not yet proven by research.
Swimming exercises almost all muscles in the body. Usually, the arms and upper body are exercised more than the legs. In competitive swimming, excessive leg muscles can be seen as a disadvantage as they consume more oxygen, which would be needed for the muscles of the arms. However, this depends on the swimming style. While breaststroke generates significant movement with the legs, front crawl propels the body mainly with the arms.
Sometimes the swimming consists of swimming laps using a conventional stroke, such as the front crawl; other forms can include different forms of exercise performed in the water, such as aqua aerobics .
Swimming is considered a sport with a low risk of injury. Nevertheless there are some health risks with swimming. Most lethal risks in swimming are due to the inability to swim. It is recommended to swim in an area supervised by lifeguards and to paying attention to the water conditions. Possible health risks range from lethal to minor inconveniences. Below is a list of these risks, ranging from potentially lethal to minor temporary inconveniences.
- Drowning can cause injury or death.
- Drowning due to adverse water conditions which may force the body under water or force water into the body.
- Drowning due to negative buoyancy, for example due to being attached to items heavier than water, e.g. medieval armour or a concrete block around the feet, or being trapped in an item heavier than water, e.g. a sinking ship.
- Drowning due to outside influence, as for example being pushed under water by another person by accident or intentionally.
- Drowning can also be caused by the inability to swim due to exhaustion or unconsciousness or a combination thereof. Besides other health risks listed below this may be due to effects unrelated to swimming as for example heart attacks and other strokes.
- Risks due to the effect of water on the human body.
- Secondary drowning, where inhaled salt water in the lungs after a near drowning starts to create a foam in the lungs that restricts breathing.
- Thermal shock after jumping into water can cause the heart to stop.
- Spending time in the water can give a wrinkled skin on the fingers, palms of the hands, and the soles of the feet. This disappears quickly without any negative effect.
- Injuries may heal slower if submerged in water.
- Risks due to chemicals in the water.
- In chlorinated swimming pools the chlorine may burn in the eyes. This stops shortly after leaving the water. Other disinfection techniques using, for example, ozone can avoid this effect.
- Breathing small quantities of chlorine from the water surface during swimming repeatedly for long periods of time, as for example in the case of competitive swimmers, can face adverse effects on the lungs.
- Chlorine also has a negative cosmetic effect on hair after repeated long exposure.
- Risks due to bacteria, fungi and viruses in the water. Water is an excellent environment for many bacteria, which may affect humans. The risk and severity of infection vary with the water quality. A selection of more common infections related to swimming are:
- Swimming and showering can cause athlete's foot (boat bug). The easiest way to avoid this is drying the space between the toes after swimming.
- Swimming can cause ear infections in the ear canal (Otitis externa).
- Cases of Legionnaires' disease have been transmitted by improperly sterilized showers after swimming. Good swimming facilities heat the shower water to 60°C (140°F) once per week during closing time to disinfect the water system.
- There is no known case of transmission of AIDS through the water, nor is there a known case of pregnancy due to sperm transported through the water while swimming.
- Risks due to physical activity in the water specific to swimming.
- Competitive swimmers may have a health risk due to overuse. Butterfly swimmers for example may develop some back pain after long years of training, breaststroke swimmers may develop knee pain, and front crawl and backstroke swimmers may develop shoulder pain.
- Long term swimmers may occasionally get some abnormal growth in the ear canal due to the frequent water splashing of water in the ear canal.
- Shallow water blackout is a condition where holding the breath causes a sudden unconsciousness due to oxygen starvation (Asphyxia).
- Exhaustion due to long swims or bad physical shape can cause drowning.
- Risks due to water and weather conditions.
- An outdoor swimmer can be hit by lightning during a thunderstorm. Lightning will usually hit the highest point available, as for example the head of a swimmer on a flat water surface.
- Strong winds can cause waves and can blow a swimmer away from land.
- Hypothermia due to cold water can cause rapid exhaustion and unconsciousness depending on the water temperature and the body conditions.
- Currents, including tides and rivers can cause exhaustion and can move a swimmer away from safety or pull swimmers under water.
- Due to the reflections in the water, the effect of the sun is more severe than on land, causing sunburn. Furthermore, swimming is usually done wile exposing most of the body to sunlight, especially some areas usually covered (around the rims of the bathing suit) or in the shade (the back of the knees). In the long term this may increase the risk of cancer and decrease the aesthetics of the skin.
- Risks due to other objects in the water.
- A collision with another swimmer or other object as for example the wall of a pool, rocks, and boats, especially the propellers thereof, may result in injuries. Severe injuries are possible after hitting an object while diving into the water. Injuries can also be caused by stepping on sharp objects, e.g. broken glass.
- Dangerous marine life can attack swimmers in self defense or for prey, often in combination with a poison.
The desire or cultural demand of modesty together with the awkwardness or unsuitability of conventional clothing in the water led to the development of the swimsuit (and in Victorian times, the bathing machine).
Women's swimsuits are generally either one-piece swimsuits of traditional or competitive style (such as the racerback) or bikinis. Also there is the monokini, in case the coverage of the breasts is neither required nor desired. However, special swimsuits for competitive swimming, designed to reduce skin drag, can resemble unitards. (See Competitive Swimwear)
Nude swimming is done:
- at nudist areas
- in Denmark, all beaches are clothing-optional unless marked otherwise
- during nudist hours in some swimming pools
- at (usually small) swimming pools in saunas
- without being formally allowed, at quiet places and hours; also called skinny dipping
- at private swimming pools and beaches, not visible for outsiders
- List of water sports
- List of swimming styles
- How to swim (From the Boy's Own Book of Outdoor Sports (early 1900s))
- List of Swimmers
- List of swimming coaches
- Swimming at the Summer Olympics
- Total immersion
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