During swimming, a person exerts a force pushing themselves forward in the water. This can be done through many methods and means, although there are only four competitive strokes: backstroke, butterfly, breaststroke, and freestyle. In all these, a swimmer's arms and hands are used to physically push the water backwards, assisted through the repetitive kicking of the feet. The arm is rotated at the shoulder and the hand is held firmly together when pushing backwards, as water going between a swimmers finger's can significantly reduce the force created from each push. Swimmers can increase their fluidity through the water by decreasing the drag created between their body and the water. This accomplished through methods ranging from the shaving of all hair to wearing small low drag suits. Professional low-drag are often thin enough that swimmers can frequently tear the suit with the wrong movement, and have become so low drag, that certain types have become banned due to unfair competition.
Freestyle and backstrokes are the simplest strokes and have the fastest time due to their ability to move the water the fastest behind them. Both strokes take the simplest measure of pushing water directly behind underneath them. Butterfly strokes do not take advantage of the level created by the human arm, and instead rely solely on the rotational motion of the arm created at the shoulder's pivot point and through straight-legged kicking. (Straight legged kicks also occur at the start of freestyle races.) Breaststrokes use the elbow and knee joints to create levers to push water around the outside of the swimmer. This method is usually the least effective, meaning times for breaststroke races are slower than similar length races of other strokes.
There are two other major mechanics to competitive swimming: the start and the flip turn. During all non-backstroke races, backstrokers start in the water, swimmers begin crouched back trying to create the most force and momentum to get a speed advantage in the water. The entry into the water is crucial, as the less drag one has, the more the swimmer's get translated into the speed of his initial swim. Along with the pre-start aforementioned methods, this is accomplished by getting the body as straight as possible when entering into the pool, with arms lined up behind the head and toes pointed. Overall, drag in swimming comparable in basics to aero drag. The flip turn is necessary in all high school swimming events, as all events are longer than the pools they are held in. To summarize the process, a swimmer inverts his direction by causing his body to somersault forward as he converts his momentum into the opposite direction through the force his legs exerts on the wall.
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