By Brandon Griggs, CNN

(CNN) — It’s the climactic week at Wimbledon, the world’s most prestigious tennis tournament, and the usual sights and sounds are on display:

Players competing in their traditional white. Well-dressed celebrities in the royal box. Fans eating bowls of strawberries and cream.

And … the grunting. Lots of grunting.

If you’ve watched much professional tennis, the grunting is hard to miss. Many top players make some sort of noise as they are striking the ball — an audible sign of effort that can range from a muffled grunt to a piercing shriek.

This has long been the subject of debate in the genteel tennis world, with many fans and some former players complaining that it’s too much racket.

“It’s not necessary,” tennis legend Martina Navratilova once said. “There’s no reason to be making that noise when you’re hitting a ball. We’re not lifting 200 pounds over our head.”

In past decades, most of the scrutiny about on-court grunting was aimed — perhaps unfairly — at women players. Former player Maria Sharapova’s world-class shrieks were once measured at 101 decibels — roughly the level of a pneumatic drill. When Sharapova faced fellow grunter Victoria Azarenka in the final of the 2012 Australian Open, one headline called it a “scream-queen” matchup. Serena Williams, one of the best players of all time, was another prolific grunter.

The Women’s Tennis Association, which oversees the women’s professional tour, addressed gripes about on-court grunting in 2012, saying it would work with coaches and tennis academies to quiet the noises players make in matches.

But more recently it’s the male players who have drawn complaints, and sanctions, for their grunts.

In last year’s Wimbledon semifinal against Jannik Sinner, Novak Djokovic was penalized a point by the chair umpire for a long grunt he made after ripping a backhand down the line. And during a quarterfinal match last month at the French Open, Stefanos Tsitsipas complained to the umpire about an “extended grunt” from Carlos Alcaraz during a pivotal second-set tiebreak. Tsitsipas didn’t like the timing of the grunt, which he said came “when I’m about to hit the shot.”

Grunting has not been a big issue so far this year at Wimbledon. Several of the most prominent grunters on the women’s side, Azarenka and Aryna Sabalenka, pulled out of the tournament with injuries. So did Rafael Nadal, whose on-court intensity is matched only by his loud exhortations each time he hits the ball.

But Carlos Alcaraz, the defending Wimbledon men’s champion, has grunted his way into the semifinals. Djokovic, who owns 24 Grand Slam titles, will join him.

So why do tennis players grunt, anyway? Experts cite several reasons. They also say that while grunting in matches may annoy spectators, it can actually improve performance.

It helps players breathe better

Some experts say grunting can help players keep a rhythm and release energy as they swing through the ball. But mostly it helps regulate their breathing, experts say.

Patrick Mouratoglou, who has coached Serena Williams and other top players, says many players are taught to grunt because, “It’s a way to breathe well while you play.”

Some people have a tendency to hold their breath in crucial moments when they are exerting themselves, but this can hinder tennis players, says tennis coach Nikola Aracic.

“You’re going to get out of breath faster if you’re not breathing properly. When you hold your breath on your stroke your body is going to be clenched up, it’s going to be stiff,” he says. “So what breathing does, it allows you to completely unload the stroke in the most natural way. If you happen to make a sound while you exhale and grunt, there’s nothing wrong with that.

“Grunting in tennis is intuitive,” Aracic continues. “I grunt when I play tennis, and I have absolutely no control over it. And the interesting thing is that as my intensity increases, so does my grunting. I can tell you personally that if I don’t grunt, I lose a lot of intensity.”

It can throw off opponents

Grunting when you hit a tennis ball can mask the sound of the ball coming off the racquet, which can make it harder for opposing players to read the shot and react quickly, experts say.

“It is not direct cheating, but it is cheating in a way, because you’re making it difficult for the opponent to hear the ball hitting the racquet, and that should not be,” Navratilova says.

Mouratoglou believes grunting also sends a signal to your opponent that you’re going to hit the ball hard, which puts pressure on them. But it becomes unfair when a player extends a grunt so long that it distracts their opponent during their shot, he says.

Some critics trace the rise of grunting to Nick Bollettieri, the late tennis instructor who trained such well-known grunters as Monica Seles, Andre Agassi and Serena Williams. They accused him of teaching grunting as a tactic, but Bollettieri pushed back.

“I prefer to use the word ‘exhaling,’” he once told the BBC. “I think that if you look at other sports — weightlifting or doing squats, or a golfer when he executes the shot, or a hockey player — the exhaling is a release of energy in a constructive way.”

It boosts velocity

Grunting while striking a tennis ball also appears to have a more tangible benefit: It can help players hit the ball harder.

Researchers at several US universities in 2014 studied college tennis players and found that velocities increased in both serves and forehands by almost 5% among players who grunted.

“Although the ‘grunting’ sound is unpleasant to opponents, fans, and officials, it seems to offer a distinct competitive advantage,” the researchers said.

Three years later, another study discovered that when it comes to grunting, a lower register is better. Researchers at Sussex University in the UK analyzed television footage of 50 matches involving top-ranked male and female tennis players and found that players who grunted in a lower pitch tended to beat opponents who were grunting in a higher pitch.

The Sussex researchers found that the pitch of players’ grunts could even predict the winner of a match long before the scoreboard reflected the final outcome, suggesting that the tenor of the grunts may offer a window into the players’ mental state during the match.

So maybe athletes in other sports will start grunting more — and more deeply. Fans, cover your ears.

Even though she’s retired, Serena Williams won’t stop. In a recent interview Williams says she modeled her grunt on Seles, one of her favorite players when she was growing up.

“And so I literally would grunt because of her, and then it just became natural … It was really loud,” Williams says. “I grunt (while) playing golf now… It’s like a part of my life.”

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