We cannot access our forehand swings directly – we only have access to the Forehand Function, a neurological process that runs in the brain, which processes our sensory inputs into movement. What physically occurs as we move is not always relevant to how we program our Forehand Function. It typically informs how we adjust our Forehand Function, but just because, physically, your body should move in a certain way, does not necessarily mean that thinking about that fact will have a beneficial effect.
In this article, we’ll dissect a real-world example of this phenomenon which occurs during forehand development.
First, A Simpler Example
The distinction between the Forehand Function and the forehand itself feels paradoxical at first. If I want to move in X way, surely I should think about moving in X way, right? Turns out, no, that’s not how the human organism works, and here’s a simple example to prove it:
Counter-rotate your head while you rotate your trunk underneath it.
Try it. Look at the image below if it’s unclear exactly the movement I mean.
This movement actually is quite trivial, but only if you know the trick: you must lock your gaze on something. Lock your gaze on the wall in front of you, and now turn left and right. Your head will effortlessly counter-rotate to hold your gaze. Dislodge your gaze – don’t look at anything in particular – and now try again, and all of the sudden, it becomes next to impossible.
This simple movement – counter-rotating the head while your trunk rotates underneath – exemplifies why we must decouple the mental process of learning a movement from the physical nature of the movement itself. In this example, the physical nature of the movement is counter-rotation of the head, but that physical reality does not necessarily imply that the verbal cue “counter-rotate your head” is the best input to make it happen. In fact, in this case, it is certainly not. The best input is “lock your gaze before you rotate.”
Hip-Shoulder Separation
You’ve probably heard the term “hip-shoulder separation” before. You’ve also probably run into the idea that the “kinetic chain” proceeds from the ground → hips → trunk → shoulder → wrist → racket. Both of those things are, physically, true.
But does that mean we should program the Forehand Function with the verbal cue “ground → hips → trunk → shoulder → wrist → racket”? In my experience, not at all, and specifically the idea of “hips → trunk” is usually actively counter-productive. Again, to the naive observer, this seems like a paradox, but it’s not. The hip-shoulder separation movement simply falls into the class of movements, similar to counter-rotation of the head, for which thinking about the physical nature of the movement does not help us perform it.
The Physical Reality
The image above shows representative measurements for the angular velocity of the pelvis and the trunk for one high-performance and one elite forehand. Basically, the researchers measured a bunch of forehands, but since plotting every single one would look messy, they only plotted a single high-performance forehand and a single elite forehand on this graph. They plotted the “angular velocity” of the trunk and pelvis – how fast they were rotating at various times.
For the elite-level forehand, factually speaking:
- At the start, the pelvis rotates faster than the trunk.
- The pelvis hits peak velocity before the trunk does.
Great! Time to tell my students, so they can sync up their kinetic chains like the pros. As you can probably guess if you’ve read this far, that’s unlikely to work.
The Forehand Function Gets Confused
Let’s focus in on #1:
At the start, the pelvis rotates faster than the trunk.
While this is true… it is true only for twenty-five milliseconds. That is such a small amount of time that, for example, your ears can barely even perceive it. If I were to play a “beep beep” 25 ms apart, you’d hear only a single beep. But when a student hears “hips → trunk”, they aren’t visualizing a delay so short it’s imperceptible; they hear “hips first, then trunk” and process those words into expected sensations that they will, in fact, be able to feel. Usually, something like:
- a sensation of the hips moving faster than the trunk
- a sensation of the hips moving without the trunk
Ah! Disaster! Neither of those two sensations should exist on a well struck forehand!
Despite the fact that the pelvis does, in physical reality, outpace the trunk for ~25 ms at the start of the swing, because 25 ms is such a small amount of time, the human brain will not perceive that timing gap as a delay. It will perceive those actions as simultaneous, and therefore a student who tries to adapt their swing until they can perceive a time delay will ultimately install a delay which is far larger than the delay we want:
- We want a 25 ms delay (very short).
- You can’t feel a 25 ms delay (because it’s too short).
- A student modifying their stroke by trying to feel a delay does not correctly install the 25 ms delay (because it’s unfeelable), and instead elongates their delay until it can be felt, leading to a delay much greater than 25 ms.
So even though a short delay exists in physical reality, the process of attempting to program the Forehand Function using it typically fails. Despite the delay’s existence, the perception of the timing between the hips and the trunk is almost always:
- the hips and trunk start the swing together
- the trunk rotates faster than the hips
It is the sensation of simultaneity which is, almost paradoxically, the sensation most likely to program the Forehand Function to produce the very nuanced small delays which facilitate the hip-shoulder separation whip in the first place. That the hips and the trunk move simultaneously doesn’t literally map onto the body’s physical timing, but we, as humans, do not have direct access to that literal, physical timing. We can only access reality through our senses, and your sense of kinesthesia will almost certainly perceive the best version of your forehand swing as: the hips and trunk engage simultaneously.
How to Feel Hip-Shoulder Separation
Here’s where it gets really interesting: we can’t feel a 25 ms delay, but we still want it. This article is not claiming that hip-shoulder separation, the physical reality, is a catastrophe – far from it, it spring loads the fascia and produces lots of easy power. Rather, it is only the “hip-shoulder separation” verbal cue, used to program the forehand function, which rarely works.
We can’t feel a 25 ms delay, but we still want it.
We need a way to feel the presence or absence of our hip-shoulder separation whip, to feel that 25 ms delay, so we can habituate it, and our sense of time fails us, because 25 ms is too short to feel. Here’s the secret: don’t use your sense of time. You can perceive the proper hip-shoulder separation as tension. Tension through the fascia in your abdomen, between the shoulders and the pelvis. Other imperceptible timing gaps are perceived similarly – as tension or stretch, not as timing delays.
Mapping Reality onto Sensations
This brings us to the holy grail of mechanical improvement. After we understand the physical reality of an efficient swing, the next, critical step is to map that reality onto an appropriate sensation. We don’t just skip straight to the cue. In the hip-shoulder separation case, we map the reality of a timing delay onto the sensation of tension through the trunk, and once we can recognize that sensation, we can use intuition to optimize the swing.
Physical Reality: 25 ms delay during which the hips move faster than the trunk.
Sensation: Tension through the abdomen while twisting. Timing wise, simultaneous.
Drills and exercises interact with sensations we can actually feel, not with what is physically happening. While it is important to understand the reality of the swing – so we can spot check our improvement process and confirm it’s actually working – it’s equally important to map that reality onto sensations, which we have direct access to as we move, so our intuition has the tools it needs to refine our game.
Drills and exercises interact with sensations we can actually feel.
(For the particular case of improving twisting power, the medicine ball is a great tool. We discuss that, as well as some further abdominal sensations, in this video.)
(Coming soon: Applying this same idea to peak velocity timing. “The pelvis hits peak velocity 35 ms before the trunk” is not a great cue, but we can map useful sensations onto that reality to train it.)
Programming the Forehand Function
The inputs to your Forehand Function are not direct facts about reality. They are sensations – inputs from senses like sight, balance, and kinesthesia. We do not, in fact, have direct access to physical reality, and so each insight from it must be mapped on to internally accessible sensations for that insight to be useful on court.
Every cue you provide to a student will be understood through sensations. The tragedy, in the hip-shoulder separation case, is that the verbal description of reality – “hips then trunk” – implies a sensation which doesn’t exist. In the version of the swing where you can, in fact, feel the hips moving first, with the trunk behind it, the swing is almost certainly broken.
The verbal description of reality – “hips then trunk” – implies a sensation which does not exist.
Ironically, I have far more success with the literal opposite cue: “trunk → hips,” because the sensations that “trunk → hips” implies end up creating the reality of hips → trunk when executed. Players try to feel:
- their trunk accelerating fast, right from the beginning.
- their glutes driving in the middle of that rotation.
#1 is good because the trunk doesn’t get stuck. When a player tries to speed up their trunk, they’re going to use their hips. That’s how the body twists – use the legs, which the trunk is attached to, and it’ll force the trunk around. #2 works because the most vivid sensory experience from the glutes is close to lockout, not right when they start contracting. Imagine performing a deadlift, for example – obviously your hips are firing the entire way, but the most visceral sensation of hip drive is right through the sticking point. In the best version of your swing, that glutes-lockout happens in the middle of trunk rotation, not at its start.
Inferring a Student’s Internal Experience
All that said, none of the sensations I’ve described here are gospel. The truth is, when you first get on court with a student, you have no idea what their internal experience of playing tennis is like. A brilliant cue for one student might be entirely useless for another, because different students feel the game differently.
A brilliant cue for one student might be entirely useless for another.
Patience is extremely important. Keep physical reality in mind, but when you get on court with a student, work as hard as you can to understand their internal experience of the game, and be aware that most students will not be able to verbally tell you what that is, even if you ask the right questions. It will be an inferential process on your part (and it probably warrants an entire article on its own). Coaching is a mutual discovery process. You are discovering the students internal experience, and the student is discovering their game, and the better you understand the former, the faster you can help them discover the latter.
