IT HAS become common behaviour in top-level tennis, like the pumped fist on winning a set and the expletive aimed at a coach after an error. “Grunting” is too limited a name for it. The noises made by modern professionals range from wounded roars to frantic shrieks. Gone are the days of hushed rallies, punctuated only by the thud of felt on strings. Like sledging in cricket (talking to an opponent to disturb their concentration) and bat-flipping in baseball (throwing the bat in the air after a sizeable hit), squealing in tennis is considered by some players and spectators to be a blight on the game.

All three vices have been around for decades. Tennis’s best-known early grunters were Jimmy Connors and John McEnroe. Stars of the 1970s and the 1980s, and hardly famed for their courtesy on court, they used to groan with ostentatious exertion. Yet if they could claim to be exhaling with effort during particularly strenuous rallies, then Monica Seles extended the practice. In the 1990s she pioneered stroke-by-stroke screeches, delivered apparently regardless of exertion. Ms Seles is one of several successful whiners to have been trained by Nick Bollettieri, an American coach, along with Andre Agassi, the Williams sisters and Maria Sharapova. Mr Bollettieri claims that the tactic is “a release of energy in a constructive way”, though he has also spoken of encouraging his younger charges to release that energy in other ways. At more than 100 decibels, Ms Sharapova’s wailing is roughly as loud as a chainsaw or helicopter. Rafael Nadal is another bellower, to the irritation of his rival, Roger Federer. But even the GOAT (the “Greatest Of All Time”, as Mr Federer’s fans call him) has been known to bray under duress.

Unlike, say, bat-flipping, grunting in tennis has been shown to give the player responsible a definite advantage. Two separate studies of college players have found that the speed of their serves and ground-strokes increased by 4-5% when they groaned. The authors of both papers note that similar gains in performance have been observed in noisy weightlifters and martial artists. The most likely cause is the extra tension created in the athlete’s core muscles by the grunt. The pitch of the grunt also seems relevant. An analysis of 50 fixtures featuring some of the world’s top 30 players demonstrated that the men hollered a semitone higher in matches that they lost, and that the difference in pitch was clear from early in the contest. It was unclear, however, whether this change was a cause or effect of the poorer performance. Players seeking further reason to unlock their inner grunter should also note the effects of the sounds on their opponents. An experiment which required subjects to guess the direction of tennis shots on a video screen found that an accompanying burst of white noise hampered their reaction times. It took them an extra 30 milliseconds to read the direction of the ball, during which it would typically travel two feet. The participants were merely recreational players, but professionals may be even more reliant on sound, since they can use it to guess the spin on the ball.

With such compelling proof of grunting’s benefits and so much to be gained from winning—the total prize money for a grand slam is typically $40-50m—it is remarkable that there are any silent rallies at all. A crackdown on excessive exhaling seems unlikely. Rumours of an on-court “gruntometer” to establish a maximum volume faded five years ago. Umpires are allowed to award points against a player who causes an opponent a “deliberate hindrance”, but rarely do so. “Quiet please”, their favourite instruction, applies only to the crowd. For the foreseeable future, fans will have to put up with the unseemly racket.