The so-called pronation movement in a tennis serve is an unusual movement of the forearm that is quite difficult to understand if you can’t execute it well.
Trying to figure out pronation and compare it in flat, topspin or slice serves can be really confusing.
I’ve written quite a few articles on the topic of pronation and how to practice it, but since the questions keep coming in, I’ve decided to tackle the pronation topic again and answer most common questions about it.
Pronation May Not Be What You Think It Is
The confusion about pronation starts actually with us, tennis coaches.
We use the general term “pronation” to describe a much more complex movement that goes on during the acceleration phase up towards the ball and the movement right after the contact.
But, pronation as defined in anatomy or medical terms is just a forearm/wrist turn.
The service motion is so complex that using the correct anatomical terms to explain what really goes on would totally confuse the players.
Here are two excerpts from a biomechanical study of a tennis serve:
“Acceleration of the racquet before ball impact is accompanied by a rapid lumbar spine rotation reversal for a right-handed server from hyperextension and right lateral flexion to flexion and left lateral flexion.”
“Continued glenohumeral internal rotation and forearm pronation occur during the acceleration stage and continue after ball contact during deceleration.”
If you follow the link above, you can get a better sense of how complex a tennis serve really is.
Hopefully you now understand why we tennis coaches just use the term “pronation” to simplify the teaching of the final phase of acceleration towards the ball and the movement after contact.
Also keep in mind that we are able to teach 8- to 10-year-old kids to serve with pronation without ever explaining to them what it is or having them ask us any questions about it.
They simply follow the drills we give them. In time, they develop the feel for the movement and are able to produce power and control with it.
My point is that you don’t need to “understand” pronation intellectually to master it. In fact, you will only understand pronation when you can execute it well – and that can happen only if you perform the pronation exercises regularly and correctly execute them.
Players mistakenly think that this finish position is pronation...
So, what we coaches call “pronation” is a more complex movement. But tennis players usually incorrectly think that pronation is the finish with the elbow high and the racket head pointing down.
That is in fact the end of the whole complex movement that started with the upward racket acceleration.
When you wonder whether you do pronation, my answer is that you do; otherwise, you wouldn’t be able to serve the ball over the net as I demonstrate in the video.
If you’re holding a continental grip and you can serve over the net, then you do pronate the forearm so that the strings can hit the ball.
However, it’s possible that you don’t maximize the potential of the whole complex movement if your forearm never reaches or goes through the same position as you see in the pros’ examples.
Is There Pronation On Topspin And Slice Serves?
If you watched the video above, then you saw me demonstrate the topspin and slice serves with no pronation.
Again, the ball doesn’t go anywhere if we don’t pronate because we simply don’t turn the strings towards the ball.
I am attempting to demonstrate the serve with no pronation but you can still see a slightly angled racket which made the ball fly away... I simply couldn't hit the serve with no pronation.
So, a similar principle applies – if your ball crosses the net, then you are pronating, but you are likely not using the whole potential of the forearm twist which, if executed correctly, gives you extra power and bite on the ball.
The only solution to that is, again, to do practical drills because you will not learn the right move by simply looking at it and thinking about it.
What Is The Difference In Pronation on FLAT Serves vs SPIN serves?
When we hit a flat serve, the pronation will complete fully, which means the forearm and therefore the racket will turn 90 degrees from the original position and hit the ball at the back “flat”.
But, when we hit a slice serve, the pronation has not yet fully completed by the time we hit the ball.
The racket face is in the process of turning, so as we hit the ball, the racket is still angled.
That’s what makes the ball spin.
As the ball flies off the racket (that’s in about 0.005 seconds), the forearm and racket continue their path because of inertia, and the pronation will complete very soon after contact.
Therefore, all types of serves (flat, topspin and slice) look almost the same at the end of the hitting phase. In all cases, the pronation will complete.
Is A Serve With A Waiter’s Tray Position Hit With No Pronation? Do I Really Need To Learn Pronation? (It’s Difficult)
A player asked me whether they really need to learn pronation because they saw Kiki Bertens hit serves with a waiter’s tray position, which suggested to the player that the serve had no pronation.
As mentioned before, if a player has a continental grip, then they pronate regardless of their backswing shape.
The waiter’s tray position just puts the hand in a position from which you cannot accelerate optimally, but you still do accelerate, and you still pronate to hit the ball.
Your forearm can actually be pronated already in the backswing!
In other words, the serve has a flaw, and the coaches and the player have not been able to correct it over the years.
But, the player is, of course, still able to serve quite well, and she does execute the pronation and the final forearm twist correctly.
I can demonstrate a powerful serve also with an incorrect forehand grip and still whack the ball 150 km/h.
I am serving with an incorrect forehand grip in a waiter's tray position and still serving fast.
The reason why most coaches don’t teach the forehand grip serve is that it doesn’t allow players to hit topspin and slice serves.
It is very unnatural and awkward to hit a spin type of serve with a forehand grip.
With a continental grip, you can serve all types of serves really well.
The real challenge is to get used to the continental grip and to the pronation movement.
It can take you a few months of regular practice before you feel comfortable with pronation movement.
But do keep in mind that pronation and the rest of the complex movements in the serve are biomechanically natural to the body!
Perhaps it’s similar to learning to play a violin. Before you learn how to play well, you create awful screeching sounds, and it seems like you have no idea what you’re doing.
But, if you persevere through regular practice, you develop the necessary feel and precision of movement to play wonderful music.
It’s similar with pronation – before you can do it well, you will feel that this move makes no sense and that you’re not really sure what you’re doing.
But, if you persevere through drills, you will train your forearm to the point where it will smoothly and powerfully execute the movement and improve your serve significantly.
Tennis is, in my view, the most difficult sport you can play recreationally, and the serve is the most complex stroke of the most difficult sport.
You don’t really have to pursue the perfection of technique, which is really challenging. Even with an imperfect serve, you can be a competent player enjoying the game of tennis.
If you do go after correct technique, then you have to put in the hours of practice and prepare yourself for slow and gradual progress.
If you still have some confusion related to pronation or you have any other questions, let me know in the comments below, and I’ll do my best to answer.
hello again Tomaz, thank-you so very much for addressing this confusing topic. I continue to tinker with my serve and your instruction has really helped me over the past few years. My question for you is: for topspin/slice serves, is there more ulnar deviation AND wrist flexion happening? It seems like flat serves maximize the full pronation. But for any spin serves, i feel like there is more ulnar deviation & wrist flexion and maybe less pronation. I hope my question makes sense. thanks again from Canada and I love your videos. – philip
Hi Philip,
Yes, you can say there is more ulnar deviation and wrist flexion for spin types of serve. At contact the pronation has not fully completed but it will complete a few hundredths of a second later.
In other words, when you look at the finish of a flat serve vs a finish of a topspin you can barely see the difference.
On a flat serve I am “pushing” right into the ball whereas on a spin type of serve I “partially” hit the ball – meaning on the side of it and not exactly on the back of it and that’s what makes the ball spin.
The ball leaves the racket in a few milliseconds of contact, meaning we can’t “do anything to it”. It leaves the racket before we can do anything to it.
Here are the differences – images taken from my Second Serve Mastery course where I compare the flat and topspin serve.
Finally, after viewing so many videos on pronation, I really understand the topic after viewing this excellent video. Thanks Tomaz:)
Hi Tomaz, great article. What is the teaching aid you use in the video? Did you make it yourself or did you buy it? You seem to be able to make the ball spin from bottom to top & right to left. Is that correct?
Richard
Hi Richard,
It’s called Spin Doctor from Oncourtoffcourt.com. It can also be purchased on Amazon.
https://oncourtoffcourt.com/spin-doctor/
The ball spins only around one axis.
Extremely helpful. Succinct and to the point. Thank you
thanks so much for your thoughtful reply, Tomaz. Yes, I have both of your online serve courses and they have helped me tremendously over the past few years.
thanks for the comparison pictures. I am forever trying to develop an effective topspin and slice serves. For any of my spin serves, it seems like the sequences of events is (in sequential order): 1. tricep extension, 2.ulnar deviation, 3. some wrist flexion, 4. then pronation is like an afterthought that completes the motion and the elbow remains “high”, like Pete Sampras’ finish. It seems like the more i focus on ulnar deviation, the more reliable the spin serve. Do you think that makes sense? – – thanks again, Philip
Nicely explained Tomaz, not just the HOW, but just as important, the WHY. I always learn a thing or three from your easy-to-digest instruction video, editing and commentary. Thanks VERY much!
DAS/Austin TX
Superb explanation of the grips, pronation and type of spin with each variation
Another great article full of insights! You analysis and detailed explanation make it very easy to understand and implement!!! Truly appreciate your videos!!! Thank you 🙂
I seem to be pronating fine but end up with only side spin.
You are likely observing your pronation after the contact and it seems fine.
If you are hitting with side spin it means that by the time you contact the ball the racket face hasn’t fully turned (your forearm pronated) so it’s still at a slight angle.
You may be off by 0.01 seconds and it will produce side spin.
Focus on feel and not so much on technique. Try to feel when you really hit the ball smack flat and try to replicate that feel.
You will not solve the 0.01 – 0.02 seconds issue with any conscious effort, it’s not possible.
Hi Tomaz, well I changed my serve last winter using the correct continental grip and natural pronation. I have the basics of a Flat , Slice and Kick serve .I try and emulate a Federer like serve in body motion. The results are I can shoot 70% near ace serves in front of my tennis instructor during lessons but when I play a match I cant hold my serve game. Usually into the net more often but also some long over the baseline. Im told to keep the toss arm up ,head up and reach up as well as toss the ball just froward into the court slightly to the right while Im at a slight left tilt (Im righty).Very frustrating.I dont feel nervous but more motivated to gte this technique down.
Hi Corrado,
When you play matches don’t ever think about technique. In matches we only aim, so just mentally visualizing the targets or trajectories.
Either serve with a completely blank mind if you can achieve that or aim in a small window above the net. Visualize 0.5 meter window above the net and aim to hit through it.
Hi Tomas. Question about slice or top spin slice. Is your aim to strike the side of ball at 3 and 2 respectively or the back center of ball?On kick serve is your aim to brush up from 7 to 1 ( clock face). Thanks. Love your teaching. Paul
Hi Paul, yes, hit the side of the ball but you still need to hit the ball somewhat dead on for slice otherwise you’ll just spin it sideways and it will drop down on the ground. You need to give it both speed and some direct power. So yes, at 3 o clock but a bit more inside of the ball. And yes, 7 to 1 for topspin.
Please explain that as you strike the ball and racket is brushing from left to right( as a righty).the rotation of the ball will begin to spin that same direction. So why does it bounce in the opposite direction when it hits the court?
Hi Antonio,
Good question. The ball is affected by the Magnus force (also called Bernoulli effect) when it’s spinning.
The same force that pushes the ball down when hit with topspin, also works with a side spin.
Check this video where I scientist demonstrates the ball flight with side spin:
https://youtu.be/23f1jvGUWJs?t=187
So because I spin the ball sideways it starts to fly in a sideways curve and that gives the ball a sideways vector.
When the ball hits the ground it’s not the spin that makes it go left (for righty slice serve to deuce side), but the sideways vector that was created during the flight.
The side spin actually wants to move the ball to the right (which is what is confusing you) but the sideways vector is stronger so the ball skids off to the left.
Hi Thomas
Your teaching is fantastic by the way. Love your work. My question to you, Is it possible to over pronate on the serve?
Thanks, Keith!
Yes, it’s possible, it happens when you are forcing the pronation too much outwards.
You will see the racket turned outwards with strings at the end of pronation and you may want to push the racket that way too consciously – or even some coaches teach that.
But the outward racket position simply just happens, what we do with pronation is to push forward toward the target for a split moment.
Also, pronation can be done too forcefully if one doesn’t relax the arm / forearm enough as it comes out of the loop since the arm / forearm needs to supinate first and it does that automatically naturally if one is relaxed.
But if one is too conscious about pronation (or trying too hard) then they will not relax at all (since they are trying hard) and pronation will feel very forced and eventually painful.