Forehand Kinetic chain

[uspta2331024484]

Who can explain the role of the left leg in terms of the kinetic chain when hitting an open stance forehand for a right-handed player?

[uspta146749877]

Please post another section as well

Probably it would be a good idea to post the same question in the section
Sticky: Have a Question for Me?

John Yandell reads the section mentioned above more frequently

julian mielniczuk
usptapro 27873

[uspta990770809]

Put the player on a roasting spit

Who can explain the role of the left leg in terms of the kinetic chain when hitting an open stance forehand for a right-handed player?

It's hard to understand intuitively how the left leg/left side of the body gets power to the right side of the body to hit the open-stance forehand. The key is to understand torque and rotational energy. It's not a question of the body pushing forward to put linear momentum into the ball.

So imagine the body spinning about a pole through the left ear perpendicular to the ground. Usually, that pole would be a little behind the left leg which would mean force from that leg would push you away from the target. But since the body is turning on that "spit", the force rotates the right side of the body forward around that "spit". Of course, the right leg is also working around that "spit" to contribute to the rotation of the body.

The actual speed of the ball comes from a transfer of linear momentum to the ball, but the force is generated by torques...and in this case, around that "spit".

I don't know where in the articles that may be delineated, but perhaps John will point that out.
don

[johnyandell]

Good explanation. The question is, other than academic interest, how valuable is it--and also how verifiable.

I think we get caught up sometimes in trying to explain things in scientific terms when only a few people have actually done any measurements that would make that truly possible.

What we can say is that in the semi-open stance and open stance set ups, when the players are in the center of the court at least, the coiling or bending of the left leg corresponds with the stretch of the left arm and about the top of the backswing. If you make that position and crush the ball do you need to know how forces flow thru some mysterious chain???

[uspta990770809]

Don't get technical with the student

John is absolutely right. Thinking about these things in scientific terms is nice for discussion purposes and those of us trying to figure out what is happening and to understand what might work better or keep someone from being able to execute a simple shot. But when you are talking to a student, the point is to get them to load the legs, stretch the arms and release. For me, I get my students to throw a 6 to 10 lb. medicine ball to feel the power come from their core. When they feel that, they are usually able to execute the shot a little better. It also helps them feel that they don't need to jump into the shot to get power.

[oliensis]

I think that addressing this question could be valuable, even if it's real tough to answer it. Value coming from raising awareness about what that left leg feels like when setting up for, and executing, and then following through on open-stance forehand...and whether it might be able to contribute more to the whole sheh-bang.

Good examples from the Stroke Archive:

http://www.tennisplayer.net/members/strokearchive/pro_men/fernando_gonzales/fg_forehand/fg_fh_center/fg_fh_center.html?FGFHCenterOpenStanceFront3.mov

http://www.tennisplayer.net/members/strokearchive/pro_men/rogerfederer/rogerfederer_forehand/rogerfederer_fh_center/rogerfederer_fh_center.html?FedererFHCenterSide1.mov

Often it seems left leg is not all that involved (other stroke archive clips, esp when F and G are pushed back a bit). But when theyre setting up aggressively, looks to me like the left leg contributes in more than 1 way:

My hypothesis, submitted for consideration:

1) left leg gets loaded along w/right leg, at least somewhat (30/70?)...and left leg contributes to thrust as you launch toward hitting zone.

2) then the left leg turns from "knee facing sideline" to "knee facing net" after thrusting, rotating roughly 1/4 turn (90 degrees) as hips do likewise.

3) as that rotation occurs, the left leg also moves forward, so that it can be landed on...and I suspect, from slowly shadow stroking myself that there's an element of "counter rotation" internally, (like non-striking hand in a karate punch, which pulls back as punch goes out) by which I mean that the pull of the abs during the stroke is transmitted through pelvic floor to pull on the muscles that connect pelvis to leg as well, so that the leg's moving forward is not an "act of doing" but a reaction to the whole dynamic action of hitting the ball.

Worth listening for next time on the court.

[uspta146749877]

A nice video to watch

A nice example to watch is

http://www.tennisplayer.net/members/strokearchive/tournament/mens/umag_fh_2006/Umag.FHs.Center/Umag.FHs.Center.html?WawrinkaFHOpenStanceCenterFront.mov

and a running variation

http://www.tennisplayer.net/members/strokearchive/pro_men/andy_murray/am_forehand/am_fh_running/am_fh_running.html?AMFHRunningOpenStanceFront1.mov

[uspta146749877]

Landing foot?

It's hard to understand intuitively how the left leg/left side of the body gets power to the right side of the body to hit the open-stance forehand. The key is to understand torque and rotational energy. It's not a question of the body pushing forward to put linear momentum into the ball.

So imagine the body spinning about a pole through the left ear perpendicular to the ground. Usually, that pole would be a little behind the left leg which would mean force from that leg would push you away from the target. But since the body is turning on that "spit", the force rotates the right side of the body forward around that "spit". Of course, the right leg is also working around that "spit" to contribute to the rotation of the body.

The actual speed of the ball comes from a transfer of linear momentum to the ball, but the force is generated by torques...and in this case, around that "spit".

I don't know where in the articles that may be delineated, but perhaps John will point that out.
don

Do we always land on a left foot ( for rightie)?

[airforce1]

Who can explain the role of the left leg in terms of the kinetic chain when hitting an open stance forehand for a right-handed player?

left leg is pulling thru

[uspta146749877]

Exception ?

left leg is pulling thru

Except of some players whose first names start with the letter D

[BrianGordon]

On the left leg during the latter stages of the open stance forward swing (right handed player):

...and I suspect, from slowly shadow stroking myself that there's an element of "counter rotation" internally

Very good!!! - so the obvious next question is why is that necessary in the overall scheme of the open stance stroke - get that and you are the king du jour of the forum in my view.

[airforce1]

On the left leg during the latter stages of the open stance forward swing (right handed player):

Very good!!! - so the obvious next question is why is that necessary in the overall scheme of the open stance stroke - get that and you are the king du jour of the forum in my view.

Is this counter rotation you hint at,
during the stroke or at the end,
after the ball is gone?

[BrianGordon]

Is this counter rotation you hint at,
during the stroke or at the end,
after the ball is gone?

Latter part of the forward swing meaning as the racquet is being swung into contact - prior to to contact - his observation approaches the heart of the kinetic difference between stance permutations - never seen anyone get even close from a mechanical perspective.

[oliensis]

Brian,
I suspect that the left leg's internal counter rotation is necessary because the left leg is the "lever" on the opposite side of the center (or center of gravity) from the hitting arm. The left leg's counter rotation is "counter" to the right/hitting arm's action, so the left leg is the expression of Newton's 3rd Law of Motion (for every action there is an equal and opposite reaction) in the context of the biomechanical system of a person hitting a forehand.

More specifically, especially since the left leg is often in the air (not planted) at the moment of contact in an open-stance forehand, and since the pelvis roughly functions as a fulcrum/platform from which the upper body rotates into the forehand (), the counter action of the left leg is needed help stabilize the pelvis/platform/fulcrum by generating a force upon it that is roughly equal and opposite to the forces generated from above by the upper body mechanics of the stroke.

Don't know if that's along the lines you are thinking, but that's my hypothesis, based on my experience in tennis and martial arts.

In Edit: In a neutral-stance forehand, we don't see the same counter rotation in the left leg because both feet are planted on the ground. The platform from which that shot is hit is the Earth's surface (court surface), not the pelvis. In black-belt Tae Kwon Do forms, one learns to strike with hands using progressively "higher" platforms: feet, pelvis, solar plexus, sternum... and subtler and subtler counter-balances/counter-rotations, so that ultimately stances can also become subtler and subtler.

On the left leg during the latter stages of the open stance forward swing (right handed player):

Originally Posted by oliensis
...and I suspect, from slowly shadow stroking myself that there's an element of "counter rotation" internally

Very good!!! - so the obvious next question is why is that necessary in the overall scheme of the open stance stroke - get that and you are the king du jour of the forum in my view.

[BrianGordon]

In general terms the mechanism you mention is valid and used – we could quibble about the details but they are not that important here. If I understand correctly, your reasoning for why it is used in the open stance stroke is simply that you can because the left leg is in the air. Why not keep it on the ground? I wonder if there is not a deeper kinetic explanation here – one in which the open stance trades technical simplicity or decreased physical effort for less overall rotational capability for the body during the primary leg drive (compared to the square stance for an identical shot).

Qualitatively comparing the placement of the legs, and the implied direction of the forces and torques from the ground during the leg drive, it seems fair to conclude this could be the case. Then your counter motion mechanism makes a hell of a lot of sense. It could be used to generate more upper body rotation given less total body rotation from the leg drive to work with. Conceptually at the extreme, this would be a zero-sum angular momentum game.

So with the open stance you get equivalent upper body rotation to the square stance (this has been quantified) in a potentially simpler or easier way – might help explain its prevalence in the game today. Anyway, I’m testing this in the lab right now – I’ll let you know what I find out. In the mean time, I think you are on the right track – kudos.