Swimming can be done using a wide range of strokes, known as «strokes», and these movements are used for various purposes, or to distinguish between competitive swimming lessons. It is not necessary to use a defined stroke for propulsion in the water, some inexperienced swimmers use a «Dog style swim», this style is derived from the movement of the arms and legs, similar to what four-legged animals do when swimming. There are four main movements that are used in swimming competitions and recreational swimming activities: the front crawl or freestyle, the breaststroke (breaststroke), the backstroke, and the butterfly stroke. Competitive swimming in Europe began around the year 1800, using mainly the stroke style. In 1873, John Arthur Trudgen introduced a swimming technique called trudgen in western swimming competitions, the crawl style was copied from the American Indians, but substituting a scissor kick for the traditional flutter kick that reduced splashing. The butterfly style was made in the 1930s and was introduced in the same decade, it was considered a variant of the stroke until in 1952 it was accepted as a separate style. The butterfly style is for many the most difficult style, the butterfly style burns more calories compared to the other 3 styles. The butterfly stroke is not easy and has a very high level of complexity, but that is perhaps why swimming butterfly is a challenge. It is clear that the figure of Michael Phelps has contributed to this style becoming popular in the last decade, especially after his gold medals at the Olympic Games (2008 and 2012) .v