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GRF - Dr. Mike Duffey

Dr. Mike Duffey of Penn State University has a great visual for the way the feet interact with the ground. The ground does nothing by itself, but when you push against the ground, you can create movement from the force that comes back at you. In this video, I will show you a sample of the direction and magnitude of the forces going into a golfer during a golf swing. With these images, you can get a clearer picture as to how the legs should push against the ground and how that corresponds with the different phases of the swing that we discuss in this system.

One important takeaway from this video is that it's not just how hard you push, but the direction that you push that influences the quality of your lower body action.

Tags: Fundamentals, Not Enough Distance, Advanced

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This concept video is looking at how the feet work with the ground better known as ground

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reaction force. So I want to thank Mike Duffy for letting me use the visual that he presented

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at the open forum. It's a great way of visualizing that it's not just about pushing

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more and pushing harder, it's more about pushing in the right direction with a combination

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of how hard you push. So we speak a lot about the direction that we need to push both

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with the trail foot and with the lead foot. Hopefully this visual helps you understand

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and kind of strengthen that visualization of what it is you're actually trying to do with

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your feet against the ground. So again, I want to thank Dr. Mike Duffy from Penn State

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University for sharing this great animation with all of the Gulf of Marit Academy members.

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I'm going to walk you through basically what all these lines mean stuff like that. I'll

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put a key over on the side for you and keep it there. If you're a Gulf instructor, this

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is going to be invaluable. If you're a golfer, this is going to be great for you to be able

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to visualize and I'll try to keep it simple enough that you can practically apply it

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to your own game. If you are a Gulf instructor, I know that starting in the fall of 2015,

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Dr. Duffy is going to have a program that you can take to learn more about this kind of stuff

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and I highly recommend it. He's one of the bright minds out there. So let's get into looking

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at how all these things change during the Gulf swing. But first let's walk through each piece.

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So this little green orb in the middle is going to be his center of mass and then the blue

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lines are going to be how each foot is pushing against the ground or the ground reaction

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to how each foot is pushing against the ground. The yellow is the combination of those

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two located at the center of pressure. So first what we'll do is we'll walk through each

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of the different phases and then we'll go through and kind of break it down into each piece.

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And the last little thing is this total frontal moment is basically showing the amount

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of rotational force or torque that I'm creating by pushing with my feet in a certain way.

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So as an example, if I were to change this and push with this left foot, you can see that

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would cause me to have a moment or a torque and make my body want to tilt over to the right.

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If I was to not push with the left at all, you could see that the combination is going

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to be just what I'm doing with the right and it's going to make me want to tilt to the left.

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So let's walk through the different phases of the swing and kind of take a look at

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how these things are changing. So here we have during the take away, you're going to push

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with that front foot slightly down and away in order to create some of this rotation to get

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onto that right side. Now at early backswing, I've shifted, you saw the yellow line shift to the

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right, so I've shifted my pressure over there and the blue line from the right foot is now pushing

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more towards my body. So basically I'm pushing slightly away from the target like this.

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As we move up towards the late backswing when the arms parallel to the ground, you can see that

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the big difference is that the right foot blue line has shifted and pointed more towards the target.

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So I'm pushing further away or basically I'm kind of pushing horizontally in order to

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create that change and it's not that I've pushed harder, it's just the direction has started to change.

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In addition, I'm pushing with that lead foot as my center pressure starts shifting back towards

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that direction. So the furthest point is going to be away from me is going to be more in here and

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then I start working towards the target. Now at the top of the swing, you can see the blue line

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from the right foot is pushing even more towards the target and the yellow line is changing that

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direction. So I'm going to be kind of shifting my pressure momentarily or when I start transition,

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I'm going to be shifting all my pressure over towards that lead foot. But at the top of the swing,

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I'm pushing with that trail foot and more of a horizontal direction. So I'm pushing away this way

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in order to get me going here. If we go through from early backswing until the top of the swing,

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you can see that the amount I'm pushing doesn't change too much, but the direction does.

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And that directional change is what helps me create this rotation for the side bend.

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So now as I go into that early downswing, you can see the right leg is no longer pushing nearly as

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much, but the left leg and the total center pressure is shifted much more to the left.

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So by the time I got my left arm parallel, I've shifted most of my pressure on to that front foot

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and you can see that it's not just pushing straight down, it's pushing towards the target a little

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bit way or a little bit as it's beginning to get into this bracing mechanic.

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Now as I get into the late downswing, I'm pushing further and further back towards my body or

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basically I'm pushing more towards the target in order to help propel my arms and trigger the release.

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The right foot is not pushing very much and you can see that it's not really driving away from the

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target anymore. I already did that during transition. Now most of the push is going to come from that

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lead side. And then when I get to impact, I'm pushing further back or pushing towards the target to

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create this ground reaction pushing me further back. And you can see that the right foot is actually

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going this way, which means the foot is pushing against the ground that way. It's more dragging and kind of

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helping to kind of stabilize rather than actually driving. Most of the drive of my legs is going to

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happen in between these two frames and then by impact, I better have all that energy out in the club

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head in order to transfer it to the golf ball. Again, thank you Dr. Duffy and if you're a coach,

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I highly recommend you look into his program to help you understand the science of the golf swing

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even better. So hopefully looking at this visual has helped you visualize what the legs are doing

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with the ground and some of this ground reaction for stuff. But essentially just walking through it,

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you'll see that the golfer is going to buy this point is kind of really pushing. So they basically

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stepped onto this right leg, which a lot of good motion drills will get you to feel,

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but they've stepped on this right leg and then I'm pushing against the ground this way and what

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happens is as I start going towards transition, I start pushing more and more that way. So you see that

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that blue arrow over the right foot as I get to kind of here, I'm now pushing more that way instead

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of straight down as I am in the takeaway. And then what you'll see is that lead foot is going to have

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the opposite pattern where I'm basically pushing kind of straight up this way by the time my arms

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are parallel or lead arm is parallel to the ground just like so. And then as I go to push,

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I'm pushing even a little bit more back as I now am transferring all that speed that I created

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down the golf ball. So I think this is a great way to kind of visualize some of that trail foot

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and lead like brace that I described. Hopefully it helps you build this little map in your mind

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of what it's supposed to look like and then I can use the drills to help build a feel which will

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strengthen what it should look like in your brain. Thanks again to Dr. Mike Duffy for letting us use this

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visual. I think it's a great way of looking at how the feet are interacting with the ground.

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