Swimming is the self-propulsion of a person through water, usually for recreation, sport, exercise, or survival. Swimmers achieve locomotion by coordinating limb and body movements to achieve a level of buoyancy and hydrodynamic thrust that results in directional motion. For example, they float to a greater or lesser extent, and move in a given direction by coordinating their forward thrusting actions, especially of their head and torso, with other actions such as stroking with their arms and kicking with their legs. Swimming is a whole body exercise that requires endurance, skill and efficient techniques to maximize speed and minimize energy consumption. Swimming is consistently among the top public recreational activities, and in some countries, swimming lessons are a compulsory part of the educational curriculum. It offers numerous health benefits, such as strengthened cardiovascular health, muscle strength, and increased flexibility. It is suitable for people of all ages and fitness levels. As a formalized sport, swimming is featured in various local, national, and international competitions, including every modern Summer Olympics. Swimming involves repeated motions known as strokes to propel the body forward. While the front crawl, also known as freestyle, is widely regarded as the fastest of the four main strokes, other strokes are practiced for special purposes, such as training and competition. Swimming comes with many risks, mainly because of the aquatic environment where it takes place. For instance, swimmers may find themselves incapacitated by panic and exhaustion, both potential causes of death by drowning. Other dangers may arise from exposure to infection or hostile aquatic fauna. To minimize such eventualities, most facilities employ a lifeguard to keep alert for any signs of distress. Swimmers often wear specialized swimwear, although depending on the area's culture, some swimmers may also swim nude or wear their day attire. In addition, a variety of equipment can be used to enhance the swimming experience or performance, including but not limited to the use of swimming goggles, floatation devices, swim fins, paddles, and snorkels.
Science
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 based on body composition, lung inflation, muscle and fat content, centre of gravity 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. Because they tend to have a lower centre of gravity and higher muscle content, human males find it more difficult to float or be buoyant. See also: Hydrostatic weighing. Since the human body is less dense than water, water can support the body's weight 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 hydrodynamically effective, swimmers can either increase the power of their strokes or reduce water resistance. However, power must increase by a factor of three to achieve the same effect as reducing resistance. 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. Swimmers may opt to do some pre-swim exercises such as "arm swings", in which they rotate their arms like a windmill, to help loosen their joints and warm their muscles immediately before swimming. Outside the pool, swimmers may incorporate strength training exercises such as squats. A 2022 systematic review, published in Science & Sports journal, found that adding certain strength training exercises to traditional swimming training may improve both short and medium distance swimming performance. The authors concluded it would be "appropriate" to have strength sessions separated from swimming sessions within a training programme but cautioned against increasing the training volume too much, to avoid "greater fatigue" among swimmers.
Infant swimming
Human babies demonstrate an innate swimming or diving reflex from newborn until approximately ten months. 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). Because infants exhibit instinctual swimming behaviors, classes for babies about six months old are offered in many locations, and formal training is recommended to reinforce these abilities. This helps build muscle memory and makes strong swimmers from a young age.
Technique
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