TENNIS PLAYERS who grunt and groan their way through Wimbledon may have an edge on their opponents.

The increasing number of tennis players who gasp or shout loudly as they hit the ball are not necessarily out of breath, they may be using the "Valsalva manoeuvre", either knowingly or unknowing.

For a split second before hitting the ball, the Valsalva grunters fill their chest, stop breathing, and then suddenly, and in some cases spectacularly, let it all out in an attempt to put more energy and momentum into the ball.

"The Valsalva manoeuvre has its origins in the greatest grunters of all, weightlifters who let it all out as they drop the weight," said Professor Greg McLatchie, surgeon and professor of sports medicine at Sunderland University. "It's thought that the action releases more energy because everything is thrown out explosively at the same time, giving them an extra edge. It also helps with focusing and relaxation.''

Dominic Bliss, editor of Ace tennis magazine, says grunting is increasing. "We don't know why, perhaps it is contagious. Women players in particular seem to be grunting a lot more now. It can be a distraction, Martina Navratilova once compared Monica Seles' grunting to a pig being cut up in a butcher's shop.''