Swimming

Swimmers perform squats prior to entering the pool in a U.S. military base, 2011

Swimming relies on the nearly neutral buoyancy of the human body. On average, the body has a relative density of 0.98 compared to water, which causes the body to float. However, buoyancy varies on the basis of body composition, lung inflation, and the salinity of the water. Higher levels of body fat and saltier water both lower the relative density of the body and increase its buoyancy. See also: Hydrostatic weighing

Since the human body is very slightly less dense than water, water supports the weight of the body during swimming. As a result, swimming is “low-impact” compared to land activities such as running. The density and viscosity of water also create resistance for objects moving through the water. Swimming strokes use this resistance to create propulsion, but this same resistance also generates drag on the body.

Hydrodynamics is important to stroke technique for swimming faster, and swimmers who want to swim faster or exhaust less try to reduce the drag of the body's motion through the water. To be more hydrodynamic, swimmers can either increase the power of their strokes or reduce water resistance, though power must increase by a factor of three to achieve the same effect as reducing resistance.[7] Efficient swimming by reducing water resistance involves a horizontal water position, rolling the body to reduce the breadth of the body in the water, and extending the arms as far as possible to reduce wave resistance.[7]

Just before plunging into the pool, swimmers may perform exercises such as squatting. Squatting helps in enhancing a swimmer's start by warming up the thigh muscles.[8]

Human babies demonstrate an innate swimming or diving reflex from newborn until the age of approximately 6 months.[9] Other mammals also demonstrate this phenomenon (see mammalian diving reflex). The diving response involves apnea, reflex bradycardia, and peripheral vasoconstriction; in other words, babies immersed in water spontaneously hold their breath, slow their heart rate, and reduce blood circulation to the extremities (fingers and toes).[9] Because infants are innately able to swim, classes for babies of about 6 months old are offered in many locations. This helps build muscle memory and makes strong swimmers from a young age.

Swimming can be undertaken using a wide range of styles, known as 'strokes,' and these strokes are used for different purposes, or to distinguish between classes in competitive swimming. It is not necessary to use a defined stroke for propulsion through the water, and untrained swimmers may use a 'doggy paddle' of arm and leg movements, similar to the way four-legged animals swim.

There are four main strokes used in competition and recreation swimming: the front crawl, also known as freestyle, breaststroke, backstroke and butterfly. Competitive swimming in Europe started around 1800, mostly using the breaststroke. In 1873, John Arthur Trudgen introduced the trudgen to Western swimming competitions.[10] Butterfly was developed in the 1930s, and was considered a variant of the breaststroke until accepted as a separate style in 1953.[11] Butterfly is considered the hardest stroke by many people, but it is the most effective for all-around toning and the building of muscles.[12] It also burns the most calories and can be the second fastest stroke if practiced regularly.[12]

Other strokes exist for specific purposes, such as training, school lessons and rescue, and it is also possible to adapt strokes to avoid using parts of the body, either to isolate certain body parts, such as swimming with arms only or legs only to train them harder, or for use by amputees or those affected by paralysis.

Timurid conqueror Babur's troops swim across a river.

Swimming has been recorded since prehistoric times, and the earliest records of swimming date back to Stone Age paintings from around 7,000 years ago. Written references date from 2000 BC. Some of the earliest references include the Epic of Gilgamesh, the Iliad, the Odyssey, the Bible (Ezekiel 47:5, Acts 27:42, Isaiah 25:11), Beowulf, and other sagas.

The coastal tribes living in the volatile Low Countries were known as excellent swimmers by the Romans. Men and horses of the Batavi tribe could cross the Rhine without losing formation, according to Tacitus. Dio Cassius describes one surprise tactic employed by Aulus Plautius against the Celts at the Battle of the Medway:[13]

The [British Celts] thought that Romans would not be able to cross it without a bridge, and consequently bivouacked in rather careless fashion on the opposite bank; but he sent across a detachment of [Batavii], who were accustomed to swim easily in full armour across the most turbulent streams. . . . Thence the Britons retired to the river Thames at a point near where it empties into the ocean and at flood-tide forms a lake. This they easily crossed because they knew where the firm ground and the easy passages in this region were to be found, but the Romans in attempting to follow them were not so successful. However, the [Batavii] swam across again and some others got over by a bridge a little way up-stream, after which they assailed the barbarians from several sides at once and cut down many of them."

In 1538, Nikolaus Wynmann, a Swiss–German professor of languages, wrote the earliest known complete book about swimming, Colymbetes, sive de arte natandi dialogus et festivus et iucundus lectu (The Swimmer, or A Dialogue on the Art of Swimming and Joyful and Pleasant to Read).[14]

There are many reasons why people swim, from swimming as a recreational pursuit to swimming as a necessary part of a job or other activity. Swimming may also be used to rehabilitate injuries, especially various cardiovascular and muscle injuries. People may also pursue swimming as a career or field of interest. Some may be gifted and choose to compete professionally and go onto claim fame.

Recreation

Children's bathing beach, Lincoln Park, Chicago, Illinois, United States, 1905

Many swimmers swim for recreation, with swimming consistently ranking as one of the physical activities people are most likely to take part in. Recreational swimming can also be used for exercise, relaxation or rehabilitation.[15] The support of the water, and the reduction in impact, make swimming accessible for people who are unable to undertake activities such as running. Swimming is one of the most relaxing activities, water is known to calm us and can help reduce stress.

Health

Chuck Sketch, a former U.S. Marine and a Wounded Warrior with the veteran swim team, swims laps during a practice session at the 2012 Marine Corps Trials at Marine Corps Base Camp Pendleton, California, February 14, 2012. Wounded Warriors, veterans, and allies competed in the second annual trials, which included swimming.

Swimming is primarily a cardiovascular/aerobic exercise[16] due to the long exercise time, requiring a constant oxygen supply to the muscles, except for short sprints where the muscles work anaerobically. Furthermore, swimming can help tone and strengthen muscles.[17] Swimming allows sufferers of arthritis to exercise affected joints without worsening their symptoms. However, swimmers with arthritis may wish to avoid swimming breaststroke, as improper technique can exacerbate arthritic knee pain.[18] As with most aerobic exercise, swimming reduces the harmful effects of stress. Swimming is also effective in improving health for people with cardiovascular problems and chronic illnesses. It is proven to positively impact the mental health of pregnant women and mothers. Swimming can even improve mood.[19]

Sport

Main article: Swimming (sport)

Start of the 4 × 100 meters men's relay during the 2008 Summer Olympics in Beijing.

Swimming as a sport predominantly involves participants competing to be the fastest over a given distance in a certain period of time. Competitors swim different distances in different levels of competition. For example, swimming has been an Olympic sport since 1896, and the current program includes events from 50 m to 1500 m in length, across all four main strokes and medley. During the season competitive swimmers typically train several times a week, this is in order to preserve fitness as well as promoting overload in training. Furthermore when the cycle of work is completed swimmers go through a stage called taper where intensity is reduce in preparation for racing, during taper power and feel in the water are concentrated.

The sport is governed internationally by the Fédération Internationale de Natation (FINA), and competition pools for FINA events are 25 or 50 meters in length. In the United States, a pool 25 yards in length is commonly used for competition.

Other swimming and water-related sporting disciplines include open water swimming, diving, synchronized swimming, water polo, triathlon, and the modern pentathlon.

A sign warns hikers on the trail to Hanakapiai Beach.

There are many risks associated with voluntary or involuntary human presence in water, which may result in death directly or through drowning asphyxiation. Swimming is both the goal of much voluntary presence and the prime means of regaining land in accidental situations.

Most recorded water deaths fall into these categories:

• Panic occurs when an inexperienced swimmer or a nonswimmer becomes mentally overwhelmed by the circumstances of their immersion, leading to sinking and drowning. Occasionally, panic kills through hyperventilation, even in shallow water.
• Exhaustion can make a person unable to sustain efforts to swim or tread water, often leading to death through drowning. An adult with fully developed and extended lungs has generally positive or at least neutral buoyancy, and can float with modest effort when calm and in still water. A small child has negative buoyancy and must make a sustained effort to avoid sinking rapidly.
• Hypothermia, in which a person loses critical core temperature, can lead to unconsciousness or heart failure.
• Dehydration from prolonged exposure to hypertonic salt water—or, less frequently, salt water aspiration syndrome where inhaled salt water creates foam in the lungs that restricts breathing—can cause loss of physical control or kill directly without actual drowning. Hypothermia and dehydration also kill directly, without causing drowning, even when the person wears a life vest.
• Blunt trauma in a fast moving flood or river water can kill a swimmer outright, or lead to their drowning.

Adverse effects of swimming can include:

• Exostosis, an abnormal bony overgrowth narrowing the ear canal due to frequent, long-term splashing or filling of cold water into the ear canal, also known as surfer's ear
• Infection from water-borne bacteria, viruses, or parasites
• Chlorine inhalation (in swimming pools)
• Heart attacks while swimming (the primary cause of sudden death among triathlon participants, occurring at the rate of 1 to 2 per 100,000 participations.[25])
• Adverse encounters with aquatic life:
  • Stings from sea lice, jellyfish, fish, seashells, and some species of coral
  • Puncture wounds caused by crabs, lobsters, sea urchins, zebra mussels, stingrays, flying fish, sea birds, and debris
  • Hemorrhaging bites from fish, marine mammals, and marine reptiles, occasionally resulting from predation
  • Venomous bites from sea snakes and certain species of octopus
  • Electrocution or mild shock from electric eels and electric rays

Around any pool area, safety equipment is often important,[26] and is a zoning requirement for most residential pools in the United States.[27] Supervision by personnel trained in rescue techniques is required at most competitive swimming meets and public pools.

A Styrofoam flotation aid being used.

Traditionally, children were considered not able to swim independently until 4 years of age,[28] although now infant swimming lessons are recommended to prevent drowning.[29]

In Sweden, Denmark, Norway, Estonia and Finland, the curriculum for the fifth grade (fourth grade in Estonia) 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 (660 ft)—of which at least 50 metres (160 ft) 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 and Belgium, the Dutch translation for the breaststroke swimming style is even schoolslag (schoolstroke). In France, swimming is a compulsory part of the curriculum for primary schools. Children usually spend one semester per year learning swimming during CP/CE1/CE2/CM1 (1st, 2nd, 3rd and 4th grade).

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. Children who have not reached Great Britain's National Curriculum standard of swimming 25 meters by the time they leave primary school receive a half-hour lesson every day for two weeks during term-time.[30]

In Canada and Mexico there has been a call to include swimming in public school curriculum.[31]

In the United States there is the Infant Swimming Resource (ISR)[32] initiative that provides lessons for infant children, to cope with an emergency where they have fallen into the water. They are taught how to roll-back-to-float (hold their breath underwater, to roll onto their back, to float unassisted, rest and breathe until help arrives).

In Switzerland, swimming lessons for babies are popular, to help them getting used to be in another element. At the competition level, unlike in other countries - such as the Commonwealth countries, swimming teams are not related to educational institutions (high-schools and universities), but rather to cities or regions.

• Cox, Lynne (2005). Swimming to Antarctica: Tales of a Long-Distance Swimmer. Harvest Books. ISBN 978-0-15-603130-1.
• Maniscalco F., Il nuoto nel mondo greco romano, Naples 1993.
• Mehl H., Antike Schwimmkunst, Munchen 1927.
• Schuster G., Smits W. & Ullal J., Thinkers of the Jungle. Tandem Verlag 2008.
• Sprawson, Charles (2000). Haunts of the Black Masseur - The Swimmer as Hero. University of Minnesota Press. ISBN 978-0-8166-3539-9.svin
• Tarpinian, Steve (1996). The Essential Swimmer. The Lyons Press. ISBN 978-1-55821-386-9.

Look up swimming in Wiktionary, the free dictionary.

• Media related to Swimming at Wikimedia Commons
• Swimmingstrokes.info, Overview of 150 historical and less known swimming-strokes