Swimming

Swimming is the method by which living creatures move themselves through water in a method not involving simply walking on the bottom. Swimming is a popular recreational activity and a competitive sport. There are many health benefits of swimming, but it also entails risks if basic precautions are not taken.

Technique

The human body is composed primarily of water, and thus has a very similar density. But since only roughly 70% of the body is water, it is slightly less dense than the surrounding water, which exerts a buoyant force on it. 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, 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.

Related Topics:
Drag - Paddle

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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.

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The torso and the legs should be kept as much as possible parallel to the surface of the water. Dropped legs or a slanted torso dramatically increase drag.

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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. This is an effect long used by boat designers, and unconsciously used by "naturally good swimmers."

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The time spent on the side should be maximized 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 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.

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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.

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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.

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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.

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A number of swimming styles have been developed based on the implementation of some or all of these principles.

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