"The word lost much of its force during the last century, especially after World War II. When Alan Jay Lerner wrote the musical My Fair Lady, based on Shaw’s play, he felt bloody was too weak to make the point to American audiences about Eliza’s low-class origins breaking through under stress. In the Ascot scene, which isn’t in the play, he has Eliza urge on her horse with “Move your blooming arse!” I remember hearing gasps from members of the audience at this extremely rude word arse when I saw the film in Britain on its release in 1964. That euphemistic blooming was rather sweet; bloody turns up a couple of times elsewhere in the film, but perhaps Lerner felt that “Move your bloody arse!” would be pitching it too strong even for his more tolerant times."

from: http://www.worldwidewords.org/topicalwords/tw...

"Move your ass" would be the US version, and I agree, it's pretty vulgar. Not sure it would do the job, either. You could always use "Get a move on!", which is informal, too, but parents or coaches might be more likely to say it.