If grunting is so helpful in tennis, why don’t more athletes do it?



MATT MORET: Welcome to Field Study, a podcast about sports and science from the Pittsburgh Post-Gazette. I’m Matt Moret.

Today’s episode is all about the not-so-mysterious power of loudly grunting during athletic activity. It’s a common topic when discussing professional tennis. If you’ve ever seen a match featuring Serena Williams, or really any elite player, you’ve probably heard voices boom through a stadium loudly enough to reach the folks at home.

So the question is, just how big of a difference does a loud burst of sound make on the playing field?

Post-Gazette reporter Chris Huffaker decided to find out. In this episode, you’ll hear from a martial arts master, as well as a couple of major league baseball players -- all of whom have incorporated grunting into their styles.

And with that, here’s Chris.

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In this July 16, 2015 file photo, Misaki Oku, right, a member of Japan's national team, practices karate with her teammates at Kokushikan University in Tokyo. (Ken Aragaki/Associated Press)


CHRIS HUFFAKER: Okay could you do it one more time? I’m going to hold the mic further away just in case it popped the mic.




HUFFAKER: Okay, yeah, that’s loud. Wow. That’s impressive! *laughs*

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HUFFAKER: You may recognize that yell. It's a kiap, used in karate and many other martial arts whenever you strike, punch, kick, and so on. That's Master Patricio Saavedra kiaping. Here he is discussing it.


SAAVEDRA: The kiap — we can say in one way — is the connection between the spirit and the environment, and the other part is to cause your body to hit or break the board, and some people say to scare your opponent, too. When we do sparring, we use it a lot. All the students use it a lot. When we do the breaking, we make the yell as soon as we hit the board.


HUFFAKER: Master Saavedra runs South Hills Karate, in the Pleasant Hills suburb of Pittsburgh. He teaches the kiap to all his students, from day one.


SAAVEDRA: We try to teach it in the way that they become natural. When you kick, make some sound. Yell, kiap, make some sound. And it starts to become slowly something natural, then we start to explain with more detail what is key about it.

What I say is that it’s not just about your vocal area. It’s more about compressing your core, and then you perform your yell.


HUFFAKER: The kiap has a mental role, focusing a martial artist’s attention on their actions, but it also has a physical role: it actually makes you stronger.

I know that might be hard to believe, but it’s true. There’s an extensive literature: a simple yell, like the kiap, can cause major strength increases, somewhere around 5 to 10 percent. At an elite level, where differences between the top athletes are marginal, 5 to 10 percent can be huge.

To learn about findings like this, I spoke with Amy Welch, a researcher who has studied the effects of making noise during physical exertion.


AMY WELCH: My name is Dr. Amy Welch, I’m a professor of health sciences at Northern Vermont University in Johnson, and my area expertise I would say is exercise and sport psychology.


HUFFAKER: In 2011, Dr. Welch, alongside her graduate student Mark Tschampel, conducted a study with martial artists, testing the power of the kiap.


WELCH: We sampled 25 people who had some martial arts experience, less than a year. I think the average was about six months of experience. And those were 25 people we considered sort of novices, therefore. And there were 25 experts who were all black belts and had at least two years of experience.


HUFFAKER: They had them do three hand grip tests three times — three times one after another, three times with 30 second breaks, and three times with a kiap.


WELCH: You sort of squeeze two handles together, and it shows you the force that’s produced on a dial. So the main finding was that, irrespective of whether they were novices or experts, they all produced greater force when they did the kiap than when they did no kiap.

The force was measured in Newtons, and there was 437 Newtons produced, on average, when there was a kiap and 408 produced when there was no kiap. That translated to about a 6% increase in power output.


HUFFAKER: Dr. Welch says the research is still in its childhood, if not its infancy. But we know from other studies testing electrical activity in the muscles, the kiap seems to make more muscle cells activate. This is “muscle recruitment,” she says.

The obvious next question is: why do only martial artists do it?

Well, they’re actually not alone. Anyone who has watched professional tennis knows this.

In tennis, the grunt is much more controversial. Grunters, particularly women, are often criticized, and in American tennis rules, loud grunting is technically banned. Officially, grunting counts as a “hindrance” to the opponent. The idea behind the rule is that players are just grunting to distract the other player.

The problem is, that’s not true.

Here’s Dr. Dennis O’Connell.


Serena Williams makes a forehand return to Karolina Pliskova during their quarterfinal match at the Australian Open tennis championships in Melbourne on Wednesday, Jan. 23, 2019. (Aaron Favila/Associated Press)


DENNIS O’CONNELL: I’m a professor of physical therapy at Hardin-Simmons University in Abelene, Texas. That’s really my primary job.


HUFFAKER: Dr. O’Connell’s wife played tennis in college, and he studies breathing, so grunting was on obvious topic for him to investigate. He’s done several tennis grunting studies.


O’CONNELL: We’ve done two on-court tennis studies and we’ve done one in the lab.


HUFFAKER: Like Dr. Welch, Dr. O’Connell had people do sets of three grunting and non-grunting actions. In his study, they did actual tennis serves and forehand swings, looking at both force and speed in different settings.


O’CONNELL: What we found was that subjects, when they grunted, their forehands and their serves were about 4.5 mph faster during grunting.

We also had them pull against a string gauge, which we attached to the poles of the tennis court, to mimic forehand and serve position. But they were doing isometric contraction. And in those cases we went up 7 to 8 lbs of force when they grunted.

So we decided at that point, well, why don’t we go into the laboratory and see what was happening in the lab. So we brought them into the lab and had them push against a force transducer where they were mimicking a forehand stroke. The racket hand was at an umbilicus level and they had to push forward.

And what we found in the lab study was that, again, grunting was significantly higher than the other conditions. This time we decided, hey, why not do four breathing conditions?

So we had them grunt, we had them forcefully exhale, we had them do a val salva maneuver, which is a straining maneuver where you don’t let air out, you just push air out as hard as you can. And we also had them do a forced inspiratory maneuver, which had them inhaling while trying to produce force.

In that study, we found again that grunting was almost 6% more forceful than a forced expiration, and it was 14% more forceful than the val salva or the inspiratory maneuver. So basically in the first study we didn’t really know how they were breathing other than that they weren’t grunting. In the second, we really tried to define hey here’s four breathing conditions, let’s see what happens. And we found the same thing that we found outside. The forces went up significantly when they grunt.

We also measured muscle activity during that, which is one of the reasons we brought it into the lab. We found that the anterior deltoid, which is a muscle important to the forehand or the serve, went up significantly. And the internal oblique, which is a muscle along the chest wall, went up significantly as well.


HUFFAKER: Unlike Dr. Welch, who gave kiaping instructions, Dr. O’Connell didn’t teach his test subjects a specific grunt. But Master Saavedra says tennis players are clearly doing the same thing as martial artists.


SAAVEDRA: You get all your energy from your core. When you are sick to your stomach, you feel very weak. And that’s because all your energy comes from there. So you swing and you yell, then you probably get more power. Professional tennis players yell a lot when they hit the ball. That’s one example you can apply.

I don’t play tennis, but I guess there’s probably some similar training. You know, they can hit the ball and compress or apply power from the core. I think it’s something similar, yeah.


HUFFAKER: Now, that doesn’t mean the distraction theory behind U.S. tennis rules is wrong, per say.


O’CONNELL: Scott Sinnett basically showed that it is distracting to the receiver of the ball, of the serve.


HUFFAKER: That’s in a 2010 PLOS ONE survey where Scott Sinnett and Alan Kingstone had subjects watch videos of tennis serves with and without grunting. They found that when the video included a grunt, viewers were slower and less accurate in determining which direction a ball would go.

And we would be remiss if we left out Dr. O’Connell’s other grunting study.


O'CONNELL: We just recently did a study with patients that had lung disease, chronic obstructive lung disease. And what I had noticed in all sorts of older people was that they often grunted when they stood up from a chair, especially a low chair. So we thought we would actually ask them to get up from a chair as quickly as they could and we would measure their power output.

And so we measured their power output and they did three reps of each particular trial.

The first one was just whatever they do normally, they stood up as quickly as possible. That takes a fraction of a second, but they had a minute rest between trials. So they did three trials of standing up as quickly as they could, however they typically breath. We didn’t ask them or tell them to do anything.

Then we randomly assigned either three trials of grunting or three trials of quiet, forced exhilation. And again, all of them were a second or less to stand up, then a minute to rest.

What we found out of that group, which was a small group of only about 50 subjects with chronic obstructive lung disease, was that really the breathing condition didn’t matter. So no matter how they breathed, their velocity really was no different.


Serena Williams serves to Dayana Yastremska during their third round match at the Australian Open tennis championships in Melbourne on Saturday, Jan. 19, 2019. (Andy Brownbill/Associated Press)


HUFFAKER: For many, grunting is just annoying. Tennis has had periodic cycles of complaints about grunting for a long time, and it’s easy to see that other sports would be similarly opposed. The country-club, semi-formal world of golf might be less fertile ground for loud yelling than a sandlot sport like baseball.

And in baseball, the grunt is making inroads. Meet Robbie Ray, a starting pitcher for the Arizona Diamondbacks.

In 2016, during a troubled stretch, he got a piece of advice from his coach.


ROBBIE RAY: We were in Miami, I was getting loose and it was one of those days when I didn’t have my best stuff in the bullpen. And he basically told me, as we were walking back to the dugout, he goes, “I just want you to throw as hard as you can for as long as you can.”

It kind of came out of that. It was me just letting it all go on every single pitch.


HUFFAKER: Ray got a text from a friend, Archie Bradley, who was playing in the minor leagues at the time.


RAY: “Dude, did they put a mic in your back pocket?”


HUFFAKER: Robbie Ray had started grunting. That season, his fastball went up a little over a mile per hour, on average, and he started tallying more strikeouts. And, when we talked during Spring Training, he said he’s planning to keep doing it.


RAY: I do it in my bullpens as well. I actually threw a bullpen today, and everyone who hasn’t heard it before was kind of joking around as well. But it is something I practice with, because if I’m going to do it in a game, I need to practice it and get it where it feels comfortable. It’s almost like second nature, like riding a bike.


HUFFAKER: His description of the purpose is even a lot like Master Saavedra’s.


RAY: It’s kind of like a mental cue, like every single pitch has a purpose. Every single pitch it’s 100%. I’m a max effort pitcher. I think it just allows me to have that mental note of taking no pitches off.


HUFFAKER: Robbie also has a theory on why it isn’t more common.


RAY: I think pitchers, for the most part, are creatures of habit. They used to doing the same thing they’ve been doing their whole lives. So it’s not something that people have really caught on to just yet, I guess.

You can’t really force it. The first game I did it, it was just something that came natural. Like, okay, here we go, we’re getting on it. It just kind of came out. So it sort of came naturally for me, whereas with other guys, I don’t know if it would feel natural for them.


HUFFAKER: As of recording time, it’s too soon to say how grunting will serve Robbie this year.

He’s not grunting alone in the big leagues. Pittsburgh’s own Jacob Stallings is a grunter, but on his swing. Post-Gazette Pirates reporter Bill Brink talked to him down at Spring Training.


STALLINGS: My hitting coach caught in the big leagues for a long time, Barry Lyons. And I used to hold my breath in whenever I hit, so I got real tense and it was kind of like a grunt when you lift, like you said you blow out sometimes when you lift. Sometimes guys grunt and hold it in.  

He said that just caused a lot of tension, and he started just having me blow out, kind of as a joke at first but kind of just to get me to feel it, and I guess I just stuck with it.


HUFFAKER: Robbie Ray thinks that if kids learning to play now watch people like him, grunting might become more common.

RAY: The way you learn is from other players who have done it and have been there, so if more guys are doing it then younger guys are going to catch on or at least try it.


Arizona Diamondbacks starting pitcher Robbie Ray throws against the Chicago Cubs during the first inning Friday, April 26, 2019, in Phoenix. (Ralph Freso/Associated Press)


HUFFAKER: For anyone who’s ready to learn, Master Saavedra is ready to teach you. He even taught me!


HUFFAKER: Okay, um, this is going to be kind of unpleasant for me, but I want to try to kiap myself. Could you tell me if I do an okay job? So I want to be trying to, from way down here, yell, right?


SAAVEDRA: Right, right. You have to inhale first and, when you yell, you compress your core.


HUFFAKER: Okay, let’s see if I can do it.

*Weak kiap*


SAAVEDRA: Hmm, no, no. *chuckles*


HUFFAKER: Yeah, that was pretty high …

*Slightly less weak kiap*


SAAVEDRA: It’s like, you want to try to push your core outside. Does that make sense? Okay, so inhale. And then the second time, you yell.


HUFFAKER: *Strong kiap*


SAAVEDRA: That’s much better, see, much better!


HUFFAKER: Now I kiap when I'm writing stories. The rest of the newsroom hates me, but a 5-10% increase in performance is worth it.

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MORET: Hopefully you enjoyed this episode of Field Study. We’d like to thank our guests for talking, and grunting, with us. Special thanks go out to Bill Brink and Ryan Winn for their help with this episode.

You can find some more research about grunting in the show notes.

Next time we will try to explain why Major League Baseball is regulating the storage of balls for the first time in its 116 year history.

Thanks for listening.


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Additional Readings:

Amy S. Welch & Mark Tschampl (2012) Something to Shout About: A Simple, Quick Performance Enhancement Technique Improved Strength in Both Experts and Novices, Journal of Applied Sport Psychology, 24:4, 418-428, DOI10.1080/10413200.2012.688787 https://www.tandfonline.com/doi/abs/10.1080/10413200.2012.688787  

O'Connell DG, Hinman M, Hearne KF, Michael ZS, Nixon SL. The effects of “grunting” on serve and forehand velocity in collegiate tennis players. J Strength Cond Res 28: 3469–3475, 2014. https://journals.lww.com/nsca-jscr/Fulltext/2014/12000/The_Effects_of__Grunting__on_Serve_and_Forehand.20.aspx?sessionEnd=true

O’Connell DG, Brewer JF, Man TH, Weldon JS, Hinman MR. The Effects of forced exhalation and inhalation, grunting, and valsalva maneuver on forehand force in collegiate tennis players. Journal of Strength and Conditioning Research. 2016;30(2):430–437. https://journals.lww.com/nsca-jscr/fulltext/2016/02000/The_Effects_of_Forced_Exhalation_and_Inhalation,.18.aspx
Unpublished: The Effects of various breathing strategies on sit-to-stand power in the elderly
Sinnet S, Kingstone A. A preliminary investigation regarding the effect of tennis grunting: Does white noise during a tennis shot have a negative impact on shot perception? PLoS One 2010. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0013148