Stroke analysis - Adelina 11 years old

[seano]

As the hand pulls forward, because it is attached to the shoulder, it starts to break to the inside "the hand will start to pull to the inside which creates a force at the butt end of the racquet that makes the racquet rotate into contact" (centripetal force), explanation around the 39:40 mark of the video. This occurs after the linear hand path and the dynamic slot.

[jeffreycounts]

I use this analog to explain centripetal force. A boat pulling a skier behind it and when the driver turns sharply, the skier will whip around quickly. That's centripetal force.

And in this case, instead of turning the boat, it’s the shoulder joint that starts the redirection.

[seano]

I use this analog to explain centripetal force. A boat pulling a skier behind it and when the driver turns sharply, the skier will whip around quickly. That's centripetal force.

[stroke]

Very helpful! Thanks Seano.

It was very quick but I heard Brian say that because the arm is attached to the shoulder it “has to start breaking” in the latter part of the pull. At that point if you allow it, centripetal force will whip the racket around “like a rusty gate”. I thought something had to slow down in order for the racket to come around, And apparently it’s because the pull starts to come inward combined with the shoulder joint that you will get this centripetal force. This seems to be like hitting the breaks in your car at speed and then things will come flying forward. But in this case the breaking isn’t deliberate but a consequence of the pull and the shoulder. And instead of coming forward like in the car, the racket comes around.

I think one key might be as BG used to point out, the model type 3 with the "independent arm action", is what separates the model Nadal Fed type 3 from a lot of the other forehands. This is tied in to me with Jeff's hitting the breaks on the car analogy.

[jeffreycounts]

Here's a great video of Brian explaining the ATP Type 3 forehand. At around the 39.00 minute mark, he explains how the centripetal force works.

https://www.youtube.com/watch?v=o2Cqwa5bxV0&t=1326s

Very helpful! Thanks Seano.

It was very quick but I heard Brian say that because the arm is attached to the shoulder it “has to start breaking” in the latter part of the pull as the pull starts to come inward. At that point if you allow it, centripetal force will whip the racket around “like a rusty gate”. I thought something had to slow down in order for the racket to come around, And apparently it’s because the pull starts to come inward combined with the shoulder joint that you will get this centripetal force. This seems to be like hitting the breaks in your car at speed and then things will come flying forward. But in this case the breaking isn’t deliberate but a consequence of the pull and the shoulder. And instead of coming forward like in the car, the racket comes around.

[seano]

Here's a great video of Brian explaining the ATP Type 3 forehand. At around the 39.00 minute mark, he explains how the centripetal force works.

https://www.youtube.com/watch?v=o2Cqwa5bxV0&t=1326s

[10splayer]

Im wondering if the angle (90 degrees or less or not) at impact has more to do with racquet orientation and the subsequent shot line then for a power release. It seem that on down the line and inside out forehands there is more of a 90 degree angle, as we know the face angle at impact is the most consequential determinant in direction

[jeffreycounts]

So... while the racquet rotates via the centripetal force (allowed by wrist flexion),.

Brian/Seano - So a player needs to "allow" the wrist flexion to happen in order to get the racket to rotate around with centripetal force.. In order for it to happen it sounds like you would have to release the wrist a bit to get this to happen, otherwise the racket wouldn't rotate around. Is that accurate? It does need to be released or relaxed, otherwise you would be stuck at 90 degrees. If I lay my wrist back 90 degrees i feel my forearm muscles engaged. If I relax my forearm muscles then the wrist seems to flex naturally.

[jeffreycounts]

Jeff, looking at that still shot of Tiafoe, he seems to have a neutral wrist, even though the racquet head is below his hand. I always thought, I guess because of that racquet head position, that he had a flexion/bent down wrist position as Khachanov clearly does. Tiafoe and Murray obviously have a significantly different set up position eleven though their wrist position seem similar.

Murray looks possibly neutral as well. Nothing like Khachanov.

[stroke]

My point was not that the wrist position was great, but that for an eight year old to create the stretch shortening cycle, as opposed to laying the wrist back from the beginning, this was probably a natural way for her to do it. And then I pointed out that players like Murray, Khachanov, Tiafoe, etc do it on their forehands, so it clearly serves some purpose in initiating the stroke. When I say "dynamic pull" I just mean creating the stretch shortening cycle where the wrist goes from a neutral position to a laid back position in a quick burst. And that's what I do see her doing, which i thought was nice, even if it's not in the most ideal manner. I mean none of the forehands below are pretty that's for sure. I'm not advocating for it. But I think there is probably a reason all these players naturally do this, one being to create the stretch shortening cycle.

wrist.jpg

Jeff, looking at that still shot of Tiafoe, he seems to have a neutral wrist, even though the racquet head is below his hand. I always thought, I guess because of that racquet head position, that he had a flexion/bent down wrist position as Khachanov clearly does. Tiafoe and Murray obviously have a significantly different set up position even though their wrist position seem similar.

[BrianGordon]

Sean is 2 for 2 - nice work.

Forearm SSC would not act to propel the arm forward. It would enhance pronation in more bent arm configurations. In these configurations there is not a direct link between the racquet rotation in the flip and shoulder external rotation (as with the straight arm). Rather ESR is a function of forearm inertia and indirectly the flip supinating the forearm. This can produce a SSC enhancement to pronation which acts independently (of ESR) to produce vertical racquet speed (proportional to the degree of bend) in bent arm forehands.

[seano]

Wouldn't the amount of elbow bend at contact determine forearm involvement?

[jeffreycounts]

That makes a lot of sense. So the only question i have left would be what affect does the ssc from the forearm muscles have? Looking at it again perhaps it helps propels the arm forward?

I'm asking based on the below quote:

"The dynamic slot creates a turbocharging effect because it brings elements of the stretch-shorten cycle into play in the shoulder muscles, and to a less important extent, in forearm muscles as well"

[seano]

There's nothing like a Brian Gordon explanation, love it.

[BrianGordon]

In the early forward swing the wrist is allowed to extend to produce the 90 degrees you show - this allows the rotating racquet (flip) to optimally externally rotate the shoulder. In the latter part of the forward swing the motion of the arm (rotation) about the shoulder (plus torso twisting rotation) produces a centripetal force on the racquet grip. Due to this force the racquet will rotate if the wrist allows it to do so. And this is what players do to align the racquet for impact. The rate of racquet rotation into contact is obviously critical and is regulated using the wrist extensors.

So... while the racquet rotates via the centripetal force (allowed by wrist flexion), the wrist musculature (extensors) is activated in the opposite direction to control the rate of racquet rotation for precise alignment. The SSC would angularly accelerate the wrist in the direction of flexion making alignment problematic at best - slap city. This would also have major implications to the ability to produce vertical racquet head speed via shoulder internal rotation. Thus wrist SSC is a show stopper to high level stroke production.