Broad shoulders are the result of skeleton structure, and some people have broad shoulders while others have not. This is genetically determined and you cannot change it. read more
Well-developed shoulder muscle can visually widen the appearance of the upper body, but swimming will only do this to a certain extent. Beginners may notice some initial toning in the upper body, but this doesn't last forever. read more
Swimmers activate/exercise this muscle constantly when swimming which over a period of time develops leading to a pronounced “V” shape and broad shoulders. They also exercise their deltoids and upper trapezius which also hypertrophies (grows bigger through exercise) leading to broad shoulders. read more