The Serve: Twist Versus Forward Rotation

[gzhpcu]

Brian summed it up in his video: tennis is a complex sport and the serve its the most complex stroke.

[seano]

Brian - Once again, the frequency of your correspondence and your insight is invaluable, it's greatly appreciated.

[BrianGordon]

So... I guess we should be specific about the various roles of trunk flexion. Is it passive or is it active - and if active what is the goal.

In the case of the diagram a "slight" forward flexion is a passive natural consequence of the previous torso rotations - indeed this is normal position regardless of the momentum base.

As I said before, in serve variations where forward rotation is lacking by design, some minimal active flexion may be required - the purpose of this is positional. The variations often requiring this are twist based and forward type but around a diagonalized axis like Fed - not that his is bad, the package works for him.

Jackknifing to me implies extensive active flexion for the purpose of directly impacting racquet head speed (based on when it occurs). Trunk flexion of this sort would however have a very minimal impact on that speed compared to the must faster rotations of the arm joints that have been shown by me and others to impact racquet speed nearing impact. It would also have downward pulling influence on the arm and racquet which is why players that try this often hit in the bottom of the net.

To me it is clear that active trunk flexion to produce racquet speed is a flaw born of failure to produce and transfer adequate forward angular momentum. The more interesting thought from the world of biomechanics is that in contrast to active flexion, that an extensor torque (reversal of flexion) would apply an acceleration of the arm forward - the old whip analogy. A presentation I did at American College of Sport Medicine conference in 2004 showed it doesn't happen that way.

Great to see that there are other mechanics junkies - keep thinking.

[gzhpcu]

Plaegenhoef’s book is still one of my favorites. Timeless, I find.

[bottle]

Protruding Buttocks

In the serve chapter of FUNDAMENTALS OF TENNIS by Stanley Plagenhoef and illustrated by Nelson Giles, every server whether famous or not has buttocks that protrude.

Is this caricature (https://itunes.apple.com/us/app/clip...6328355?mt=8)? Judging from Plagenhoef's text, I don't think so. Is it intention, i.e., on purpose? Yes.

Next question: When should the buttocks get that way? And how fast or how slow?

I'm thinking right now I might like to raise the right foot with the right hip as arm bends. Hips to go backward to cantilever against shoulders leaning forward as if to form a hammer head. The rest of lean could then come from the feet.

No jolt: I get that, although one of my favorite tennis writers of all time, John M. Barnaby, advocated that as prime ingredient of a huge cannonball on page 72 of his book RACKET WORK: THE KEY TO TENNIS: "When the fanny moves back it accelerates the top of the torso forward and down."

But I am more than willing to accept that forward push on the ball could with more efficacious spin come from somewhere else.

Note: In one of Plagenhoef's pen-drawn sequences, Owen Davis lifts his foot first before his hip bumps upward and backward. Will have to try that too as soon as I come back from therapy.

Favorite word: "decrepit."

[seano]

Stotty - Your student in the video hardly "loads" his back leg at all. When he brings his back leg up to the pinpoint stance, he brings his back foot past the front and has all the weight on his toes. His back hip is hardly turned. Notice the difference between the angles of the front and back feet to the ground. The front foot has better weight distribution, while to back foot is only on the top of the shoe. To me, that's why he has too much twist rotation and "jackknifes".

[stotty]

Brian, is this relevant? From Stanley Plaegenhoefs "Fundamentals of Tennis".
Is the “juttung buttocks” a sign for what you meant?

Jutting buttocks is an amazing observation by Stanley in a book written so long ago. Most books back didn't even consider such aspects or even notice them.

Brian - To help me further understand why "jackknifing" of the trunk (flexion) is not ideal, could you please give me a practical explanation using Roger Federer as an example? Roger's serve is widely considered one of the best on tour and Tennisplayer has video of him still raising up even after contact, yet he does "jackknife" to some degree. What can Roger do differently so he doesn't "jackknife" yet makes his serve even better? Thanks once again for your input.

Some folding of the body would seem entirely natural. I, too, wonder to which degree folding would be normal or acceptable.

Some time ago I posted a clip of a young man with a powerful serve but who, in my opinion, jackknifed. In the clip he is bending right over, which in turn seems to badly affect his landing. He does serve well, though, and it's amazing how well he's overcome this deficit. I did work on his serve to rectify this but subsequently moved away and got a job in the neighbouring county.

Here is the clip: https://www.dailymotion.com/video/x6u5i05

[gzhpcu]

Another question Brian: to what extent does the physical makep of the player set the optimal biomechanical serve motion for him/her?

[gzhpcu]

Brian, quoting from Plaegenhoeff’s book, describing the serve motion, “trunk angular motion is aiding the arm motion The slightly bent body position at impact is characteristic of all good servers.”

[seano]

Brian - To help me further understand why "jackknifing" of the trunk (flexion) is not ideal, could you please give me a practical explanation using Roger Federer as an example? Roger's serve is widely considered one of the best on tour and Tennisplayer has video of him still raising up even after contact, yet he does "jackknife" to some degree. What can Roger do differently so he doesn't "jackknife" yet makes his serve even better? Thanks once again for your input.

[seano]

Brian - The trunk flexion tidbit is fascinating and contrary to several videos I have seen from "so called" ATP/WTA tour coaches. They stress the importance of the trunk flexion. Very thankful to have your insight and can't wait for the upcoming months for more on the serve. The videos and your correspondence are invaluable, thank you again.

[gzhpcu]

Brian, is this relevant? From Stanley Plaegenhoefs "Fundamentals of Tennis".
Is the “juttung buttocks” a sign for what you meant?

[bottle]

This is one guy who will chew on this. Fun.

[BrianGordon]

Hi All:

gzhpcu - glad my video potentially helped your serve. The video you posted describes a cartwheel very different from my definition. I'm describing a lateral rotation of the entire torso around a forward axis - the server in the video is simply tilting his shoulders (torso remains upright) - very different than a torso rotation and not a "cartwheel" in my world.

For bottle and others on older versions of the twist oriented serve - Certainly respectable serves can be hit with the twist based mechanics and to an extent overheads are still hit that way (not having the time and/or static conditions to set up the full forward rotation). It requires a different contact point and segment orientation to allow the twist to help the arm segments.

My point is that much "bigger" serve potential is available from the forward rotation oriented mechanics and I've seen that is what big servers tend to utilize. This comes with a cost however in that it is very dynamic requiring a lot of energy and force output. For many (including myself in my decrepit state) the twist oriented approach, or a hybrid, is a much more reasonable alternative.

The video stotty posted is interesting in that it represents a hybrid - the left leaning torso (also evident in the forward rotation version) optimizes the upper torso twist (around the tilted torso axis) such that it aids the arm segments more vertically. The difference from the forward version is that twist is generated from a twist influence from the ground and lower body whereas in the forward version the upper torso twist is derived from the forward angular momentum - big difference.

For seano and regarding trunk flexion - There is not much discussion about this (from me anyway) because on a well executed forward oriented serve this motion of the torso is a flaw - a major flaw at the extreme. Flexion will be evident only if not enough forward angular momentum is generated by pushing on the ground - in this case the trunk flexion is one last ditched effort to get the upper torso moving forward. But... this has a negative influence on the progression of the arm segments and interferes with the upper torso twist influence on arm progression - bad thing.

Based on this hopefully it is clear that should one NOT have adequate forward rotation of the entire body by design (twist based or forward based around a diagonal axis like Fed) some trunk flexion may required to compensate. That is why the serve is so fascinating to me, there are so many variables packed into a very short period and it is interesting to see the variety of solutions individual players build or acquire.

I'm hoping some of these things will be explained more in upcoming videos - don't remember so I'll find out with everyone else. Interesting points by all and a very good discussion - thanks.

[bottle]

Oh Boy. Now I Get to Possibly Reverse Myself.

And thus make myself seem like a silly person. Like someone who has loved John McEnroe all his life but now hates him for thinking that a referee should cool it and not mess up a U.S. Open final.

If cartwheel starts before foot lifts in a Jack Kramer serve, it can start with pressure from quads and other muscles in both legs even though left leg will never leave the court.

Can, I say. But that isn't what happens in this clip: https://www.tennisplayer.net/members...ServeFront.mov