The opponents of tennis players who grunt when they strike the ball over-estimate the strength behind the stroke, researchers have shown.
Loud grunts are very much a feature of the modern professional game – and very much a source of irritation to those on the other side of the net.
Some in the latter camp have gone so far to suggest the grunting constitutes an unfair attempt to distract.
Martina Navratilova once claimed the grunts masked the sound of the ball and the racquet making contact, thus making it harder to judge the trajectory correctly.
Sport stories of this type often go unchallenged, or at least unproven, but a team of researchers led by Florian Müller and Rouwen Cañal-Bruland, both from the Friedrich Schiller University, in Jena, Germany, decided to put the matter to the test.
What they discovered is that grunting during a tennis match does indeed have an effect – but not the one Navratilova claimed.
To test the contention, the researchers used experienced tennis players as volunteers, and played them footage of on-court serves and volleys in which one of the participants grunted at each stroke. After each bit of video, the volunteers were asked to predict the direction the ball went in and the distance it covered.
Unknown to the them, however, was the fact that Müller and colleagues were manipulating the volume of the grunts.
The researchers found that the presence or absence of grunts made no difference to the volunteers’ ability to predict the direction in which would move, no matter how loud the noise.
There was, however, a definite relationship between the volume of the grunt and the distance the ball was predicted to fly. The louder the grunt, the further the volunteers’ predicted. The effect remained even when the grunt was delayed until after the ball had been struck.
The reasons for the outcome remain obscure, but Muller and colleagues point to earlier research that found that the act of grunting led to a contraction of abdominal muscles and thus the generation of a bit of extra force in the shot.
And tennis professionals, of course, would know all about that.
“We assume that players account for the physiological benefits provided by grunting,” he explains.
The research is published in the journal PLOS One.