Berlin: Grunting may not make it harder to predict the tennis ball's trajectory by masking the sound of the racket striking the ball, according to a study.
Exceeding noise levels of 100 decibels, the grunting sounds produced by some tennis players when hitting the ball are on par with motorbikes or chainsaws, said researchers from Friedrich Schiller University in Germany.
While fans react to these impressive exhalations with either annoyance or amusement, the habit has also been a source of intense debate among professionals, they said.
For instance, American tennis star Serena Williams has said that she is not bothered by opponents grunting in the heat of the competition.
In contrast, former world number one Martina Navratilova has complained that grunting masks the sound of the racket striking the ball, making it -- unfairly -- harder to predict the ball's trajectory, researchers said.
In the study published in PLoS ONE journal, researchers conducted a series of experiments in which experienced players were shown video clips of rallies from a professional tennis match.
After observing players hitting the ball, they had to work out the ball's trajectory and indicate where it would land.
Largely unnoticed by participants, though, the intensity of the grunting noises was manipulated.
Results indicate that grunting does have an effect -- but not the one claimed by Navratilova.
There was no evidence that grunting caused a distraction effect, researchers said.
In spite of the supposed irritation, participants' level of error in predicting where the ball would land was the same -- regardless of the intensity of the grunts.
Instead, it was shown that the louder the grunting, the further the participants assumed the ball would fly, researchers said.
This reaction was observed even when the noises could only be heard after the racket had made contact with the ball, as is usual in many professional matches.
"We assume that players account for the physiological benefits provided by grunting," said Florian Muller from Friedrich Schiller University.