Forehand Kinetic chain

[oliensis]

Brian,
Thanks for the kudos. But my real motivation was to get the (thorny) crown that goes w/ being king du jour...8-)

The way you describe things is very sympatico to how things "look" to me.

One clarification. I wasn't suggesting that THE "reason" for the counter rotation of the left leg was that it was off the ground at contact...just that that's one signpost along the way that's indicative of the different vectoral(?) dynamics at play w/ the lower body in open stance vs. square (neutral) stance.

Looks to me like in neutral stance forehanad the rotational dynamics of the upper body are sitting on top of the sinking and then linear momentum generated by the lower body. But in the open stance you have a somewhat more advanced set of rotational dynamics at play that are a bit more sophisticated...which is why, I think, it still makes sense to teach beginners to step into the forehand...and later on to "let" the open stance develop at least significantly on its own.

And by the way, I always enjoy your work. Very rigorous stuff!

Best,
ao

[airforce1]

I guess I don't understand counter rotation. Having looked at open stance Fed FHs, other than compensations for tough CPs, all i see is pretty much a switch of the left hip around to the back as the right hip drives thru and around.
Where is something turning counter?
thanks,

[uspta990770809]

I guess I don't understand counter rotation. Having looked at open stance Fed FHs, other than compensations for tough CPs, all i see is pretty much a switch of the left hip around to the back as the right hip drives thru and around.
Where is something turning counter?
thanks,

Remember the song: leg bone is connected to the knee bone is connected to the thigh bone, etc...."

The left hip is not independent of the right hip. They are connected. If the spine and core are holding the head relatively stationary, the left hip back has to push the right hip forward and vice versa
don

[uspta146749877]

Location of an axis of rotation

Remember the song: leg bone is connected to the knee bone is connected to the thigh bone, etc...."

The left hip is not independent of the right hip. They are connected. If the spine and core are holding the head relatively stationary, the left hip back has to push the right hip forward and vice versa
don

A minor point for this conversation is a location of an axis of rotation.
There are at least two possibilities:
1.perpendicular to a ground going through a head and a center of a core
2.perpendicular to a ground going upwards through a left foot


In the case#2 a counterweight factor could be less pronounced

[oliensis]

I guess I don't understand counter rotation. Having looked at open stance Fed FHs, other than compensations for tough CPs, all i see is pretty much a switch of the left hip around to the back as the right hip drives thru and around.
Where is something turning counter?
thanks,

There are a variety of ways this can work, I think. But one way, as an example, is (for right-handed forehand) that the left leg can be moving forward as you land on it, even as the body is rotating from left-side-forward counter-clockwise to right-side-forward. In this case, the counter-rotation is the left leg's moving forward as the righth leg is launching, and then, eventually, subsequently landing even further forward (toward net) than the left leg.

e.g., http://www.tennisplayer.net/members/...anceFront1.mov

[oliensis]

Very well put, I think.

A minor point for this conversation is a location of an axis of rotation.
There are at least two possibilities:
1.perpendicular to a ground going through a head and a center of a core
2.perpendicular to a ground going upwards through a left foot


In the case#2 a counterweight factor could be less pronounced

This last is what I was trying to get at saying that the dynamics are different on square stance (#2 above) than open stance (#1 above) forehand.


As a corollary, and varying case:
When rushed, and this is sub-optimal in my view, but is a defensive adjustment to sub-optimal position, sometimes the axis or rotation is around the right hip (Fed does this on high balls often when he's pushed way back), so that his left foot actually moves backwards, away from the net, and lands behind the right foot as he's rotating away from the net...but this is a whole 'nother related but different dynamic (I think).

[uspta146749877]

The last scenario

Very well put, I think.



This last is what I was trying to get at saying that the dynamics are different on square stance (#2 above) than open stance (#1 above) forehand.


As a corollary, and varying case:
When rushed, and this is sub-optimal in my view, but is a defensive adjustment to sub-optimal position, sometimes the axis or rotation is around the right hip (Fed does this on high balls often when he's pushed way back), so that his left foot actually moves backwards, away from the net, and lands behind the right foot as he's rotating away from the net...but this is a whole 'nother related but different dynamic (I think).

The last case described is consider either sub-optimal or HIGHLY sub-optimal
in terms of "continuity" and balance.
Some references and a comparison to Sampras TBD

[oliensis]

Examples of different central pivots and degrees of counter-rotation of left leg

Fernando Gonzalez: Open Stance w/ body torquing around vertical axis of (roughly) the spine (and w/ some counter-rotation of left leg).

http://www.tennisplayer.net/members/strokearchive/pro_men/fernando_gonzales/fg_forehand/fg_fh_center/fg_fh_center.html?FGFHCenterOpenStanceFront1.mov

Agassi: Neutral Stance w/ body torquing around vertical axis of left hip

http://www.tennisplayer.net/members/strokearchive/pro_men/andreagassi/aa_forehand/aa_fh_center/aa_fh_center.html?AAFHCenterNeutralStanceSide.mov

Now here are some odd ones:
Federer in neutral stance, but w/ axis of rotation in right hip, and w/ left leg moving back from neutral stance:

http://www.tennisplayer.net/members/strokearchive/pro_men/rogerfederer/rogerfederer_forehand/rogerfederer_fh_center/rogerfederer_fh_center.html?FedererFHCenterSide4.mov

Federer semi-open stance w/ axis of rotation in right hip and left leg moving back after hit

http://www.tennisplayer.net/members/strokearchive/pro_men/rogerfederer/rogerfederer_forehand/rogerfederer_fh_center/rogerfederer_fh_center.html?FedererFHCenterFront1.mov

(is this a consequence of a lack of counter-rotation of left leg?)

Federer open stance w/ axis of rotation in center (spine), but w/ so much total rotation that even w/ brief counter-rotation of left leg, that leg still gets whipped around to land behind, rather than in front of him.

http://www.tennisplayer.net/members/strokearchive/pro_men/rogerfederer/rogerfederer_forehand/rogerfederer_fh_center/rogerfederer_fh_center.html?FedererFHCenterRear2.mov

Same for Fed, but offensive shot (when he lands on retreating left leg it's not always defensive and sub-optimal, sometimes a function of so much rotation that the left leg's gotta go back after it goes forward, just like the racket follow-through)

http://www.tennisplayer.net/members/strokearchive/pro_men/rogerfederer/rogerfederer_forehand/rogerfederer_fh_center/rogerfederer_fh_center.html?FedererFHCenterCrosscourtFront1.mov

More normal Fed w/ open stance--left leg lands moving forward (at least a little).

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

[jperedo]

hip extension?

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.

AO,Brian -
Is this counter rotation the result of hip and/or lower back extension?
I noticed that hip/back extension is more prevalant in open stance, moreso than neutral stance.

[oliensis]

Not sure what you mean by extension of the hip and lower back.

Best,
ao

[jperedo]

By hip extension i'm referring to an increase in the angle between leg and torso. Here's a URL showing the movement, also attached a picture of back extension which is similar.

http://www.exrx.net/Articulations/Hip.html

Also attached is a comparison of Verdasco at the start of the unit turn, and after hip/torso rotation on an open stance forehand. Note how the angle between his left leg and torso has increased suggesting hip extension.

This seems to be more prevalant in open stance compared to neutral stance hits.

[oliensis]

AO,Brian -
Is this counter rotation the result of hip and/or lower back extension?
I noticed that hip/back extension is more prevalant in open stance, moreso than neutral stance.

In my view, and if I'm understanding you correctly (which I may not be), the greater extension is a RESULT of the "explode" phase of the "load, explode" sequence, which tends to be more extreme in open-stance forehand than in neutral-stance forehand.

The counter-rotation thing is, I think, on the "other end" of that open-stance process. Once you load, then explode, and rotate hard as you're hitting, extending, and then following through, the counter-rotation occurs fairly naturally as your body maintains a kind of "net equilibrium." Which is to say, if your left leg (on righty forehand) doesn't counter rotate, then the angular momentum generate by the swing will end up turning you way around, so that your left leg will land behind you on the follow-through. (Federer does this sometimes.)

Others may have a different and/or better answer for you. But, if I understand what you're asking, that's what I have to offer.

Best,
ao

[jperedo]

I see now... thanks for the clarification

[airforce1]

Guess I'm the slow one on this, as I only see rotation, but not seeing the counter aspect?

[BrianGordon]

jperedo- trunk extension is a different axis so not directly related - however it is indirectly - long story - more later.

Adam- will be in Manhattan in two weeks if you feel the need to buy me a beverage for copying and shipping expenses.