Friends in line: Students from the Hayes School of Irish Dance gearing up for St Patrick's Day, from left, Audrey, Bridget, Anna, Camille and Kate. Photo: Meredith O'Shea
To keep the hems of their skirts under control. Or maybe it's because they're so bunched up together in a line it's impossible to move their arms anyway.
There is no accepted reason why Irish dancers keep their hands down while on the reel. Legend has it, the British didn't want the Irish to dance - so in case they were spotted through a window by a Redcoat, they only danced from the waist down. Given the racket their feet would have made, this seems a daft strategy.
Whatever the case, the question will no doubt raises its head again as St Patrick's Day revellers gather in Edinburgh Gardens on Sunday with their green beer and their ''begorrahs'' and watch a new generation of Irish dancers all but die above the waist while seemingly possessed in the legs by the frenzied devil himself.
Fancy footwork, Irish dance class
Irish dance students with Thomas Wilson who is representing Australia in the next World championships.
''Because it's fun,'' says Camille Brunacci, 7, explaining the technical aspects of the dance that, for a time, held the world agog.
Does Camille - who is dancing in the gardens with her sisters Bridget and Audrey, and her best friend Anna, and also Anna's sister Kate - know that Irish dancing once ran on Broadway?
''Yep. My teacher used to be in Riverdance,'' she says. ''We looked it up on the computer.''
Camille's teacher is Conor Hayes, who toured the world with Riverdance for nine years, including 18 months on Broadway and dancing at the Grammys. The son of Irish migrants, he started dancing at St Matthews School in Fawkner when he was six. ''It was a good way to get into something retained from where we had come.''
During the Riverdance craze, dance schools in Melbourne couldn't keep up with demand. Now some schools are struggling.
''It's a good dance style for beginners because there's so much footwork involved,'' he says.
''They get a sense of accomplishment from day one.''