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In this video we're going to break down the center of mass versus center of pressure discussion.

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So there's a really hot topic in golf right now. If you haven't heard of it, it's looking at ground force

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reaction and specifically looking at center of mass versus center of pressure. So I'll give you a couple

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ways that you can kind of visualize and how you can understand how it applies to your swing.

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I've got a couple different yardage sticks I'm going to use as different kind of reference guides.

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So we'll start with just the two-stake model. So we'll call the orange. This is going to be where my center of mass is.

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So that's roughly going to be around where the middle of my body is.

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So if I, if I was to go like this, the middle of my body is kind of somewhere out here.

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It's not truly where my belly button is. It's if you take all the mass of my body and you kind of average it out.

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Now the yellow stick, this is going to be more my pressure. So right now, it's balance between my two feet.

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I can shift all my weight here or all my pressure over here or I could shift all my pressure over here.

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And for a split second, I could have my mass still here and my pressure there by picking out my foot.

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So these two different objects are going to help us create moment arms and torques. Now these are some fancy words for the forces that I'm creating either against the ground or up against the club.

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Now, and we should quickly break down kind of why we want these longer moment arms.

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When it comes to how I'm applying force against the ground, the magnitude, so how much I'm pushing, the direction and the how long were the impulse, which is the force time's time, all are going to factor into this equation.

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So what happens is if I have my mass right on top of my pressure kind of like this, it's very hard for me to create any type of lateral force.

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It's essentially, and the reason is these two are right on top of each other, so I basically have what's called no moment arm. There's no distance between these two.

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To understand that moment arm concept, I always use the example of opening a door, right? So we'll imagine that I've got a door right here and here's my hinge, right?

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Is right over on this side. So they would put the door knob over here where I would turn it and then a small amount of force over here is going to move it at time.

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Now they could have put the door knob right next to the hinge, but if I apply that same amount of force, it barely moves it compared to that same amount of force down here.

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The reason is because of the distance away from this axis of rotation, it's going to increase, well, basically the formula is the force times that distance.

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So the greater the distance, the less force I actually have to apply to get a big force.

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If these two are right on top of each other, I can't anything where I try to push in one way or the other is going to be all muscular. I'm not going to have any of this kind of mechanical advantage.

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So the times in the golf swing where this ground force reaction stuff is really important is going to be the early stages of transition or from the top of the swing until about delivery position.

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The neat thing is it's going to shift. It's going to go from one side where I'm kind of building to another side once I start bracing that I better have some distance between these two to allow me to capitalize on this little kind of door example.

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So before we jump into the specifics of how to apply this swing, I always like to run through kind of how you can look at ground reaction force in general.

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So for example, if I was to jump, I'm going to push against the ground. Now if I had a little thing reading how much I'm pushing against the ground, what you would see is as I lower myself down. I actually unweight slightly so you would see the pressure as I'm going down. I'm actually not pushing against the ground very hard.

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That'll help ease centrally load my muscles. So then I can spring up so I accelerate against the ground and that causes me to go up.

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I push against the ground. The force coming back from the ground allows me to take that force, transmit it through my body and create it into upward motion.

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Now if we looked at kind of lateral movement or horizontal movement.

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If I want to walk forward, I'm going to push against the ground that's going to cause me to go forward. Now if I'm standing like this where my mass is pretty much on top of my pressure, I'm going to slightly move my mass forward and that allows me to not have to push as hard to go forward.

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If I was running or what you'll see sprinters do in the starter blocks, is they'll get their their mass as far forward as they can. So now two things.

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I'm pushing more horizontally and any amount that I push is going to transmit immediately into forward motion because I have this huge moment arm.

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The one caveat is the same reason why we as golfers were spikes and why sprinters were cleats as well is I need friction because if I start pushing too hard and the ground is not pushing back hard enough my foot's going to slip and it's not actually going to create motion.

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So there we've got the easy ones which is up and down side to side then you've also got rotation rotation is a little bit trickier because basically you're going to look at wherever the the object is.

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In order to create rotation I want to push perpendicular to that axis of rotation.

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Right. So if I were to push this way I'm not going to get nearly as much rotation out of it as if I pushed 90 degrees to wherever that center is.

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So what ends up happening in the golf swing is in order to create rotation, I'm going to push that foot back that way.

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And I'm going to push that foot that way and those two are going to create this rotation or spiral mechanic.

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Now what I frequently see is more people do this where they push this too much that way and then this one.

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It's going to tend to be more like that and so they don't get quite as much rotation as they could if they were to optimize it.

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So that's why in the early extension section we talk a lot about the push the ground away from you that's really to get this model of kind of pushing more in this back 30 back 45 instead of all the way back behind me.

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So it's a rough break down as far as how the feet interact with the ground. Now we have to explore a little bit this how do I control my mass compared to this pressure.

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So when I make a backswing part of the reason that we want to be somewhat centered is so that my mass is here, my pressure is here that allows me to push against the ground and kind of create this rotational speed.

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One of the other things is the more that I stand up right that actually tends to bring these two together.

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The the further that I drop down I should say so I'll exaggerate it right if I was to drop down a lot now my mass pushing through the foot is going to be like this if I was standing up it's pushing like that so I'm not going to get as much horizontal movement.

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Easy way to illustrate that is if I was looking at I was used to like to watch Barry Sanders change direction.

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He was a famous football player and he would get really low to the ground so because he would be low to the ground.

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He could have his mass he could have a huge moment arm between where his pressure was with his cleat and where his mass was where someone who was a little bit taller trying to change direction they wouldn't be able to apply nearly as much force.

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So we can go off by keeping this centered pivot in the backswing now I can push from this pressure over here on the right to start moving the mass to the left.

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Now my mass doesn't move as fast as the pressure does. I'm going to shift my lower body but my upper body stays a little bit more centered so the pressure goes from pushing here to pushing here to help me now start that bracing process.

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The tricky thing is all of that's going to happen between there so I go from pushing to pushing kind of as I go step step.

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Now part of the reason why you'll see a lot of golfers lower during those pushing phases you know someone like Tiger someone like Roy you'll see them drop down in order to create more friction against the ground so that they can apply more of these sheer and rotational torques or twist their feet against the ground.

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So that's a lot of kind of complicated phrasing and science to understand how the body is working with the ground.

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Now here's the one caveat I've talked with a number of other kind of applied golf sports science guys and I my personal opinion is that good ground reaction force is more of a sign that you're doing a lot of things right then something that you can ultimately train.

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It's kind of like if I had you squatting and I put you on a force plate and I put some weight on your back and had you squat down and I said okay that was good.

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But really good squatter is going to squat more than that or so why don't we just put more weight on you.

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You might look at me like I'm crazy but that's essentially when you tell someone hey you know push a lot harder against the ground.

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It could be that the arms and the club are out of position and so they can't push harder at the ground and you kind of have to clean that up stuff that stuff up first.

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Similarly if I cleaned up you know you're knee tracking your core activation your shoulder and scapular stability.

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Then we can safely add more weight and we can get you to push against the ground harder in that squad metaphor.

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So if you get on a reading and you see that you've got some some force or some pressure or weight distribution issues.

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I would always look at the face to path relationship first make sure that that is relatively solid before you're going to be able to really maximize any of this ground stuff.

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So that's always my take I know that there guys that go to the ground first.

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But my personal preference I've had more success cleaning up the face and path and then creating the speed with the body or then addressing how to create speed with the body rather than vice versa.

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Because it's very hard to create more speed and better force and pressure against the ground.

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Whether it's in the creating speed or the bracing to transmit speed.

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It's very hard to add speed if you know that that's going to make you contact the ball worse.

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So hopefully that helps you visualize helps you understand if you have a little bit more of a centered pivot on both sides if your body lowers slightly especially during transition.

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If you then when you start pushing through that lead foot.

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If that creates a little bit of this lift back move both of those are going to be the big times where especially in this frontal plane we're going to be able to maximize these center mass center pressure relationships.

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And that's ultimately going to help give you the most efficient way to create speed in the handle.

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As long as you can direct that to the golf ball I'll help you hit the ball far and straight.

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So with a club you can see that I'm pushing through with that right foot and then I'm pushing through with that left foot.

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Now the important thing is not just how much I push that's why I started this by saying there's those three important factors.

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How long I push and the direction that I push are just as important as how much I push and I tend to find that most people struggle with the direction or how long.

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So from a practical application I'll tend to say hey that was good just I want you to feel like you push a little bit longer or.

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Hey that wasn't too bad except you pushed more that way I want to push a little bit more that way that will help kind of create some of this side bend movement and then when I had that front foot that will really help.

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Create some of this side bend movement so don't get caught up on how much I think that's the last one that you can really start trying to amplify but worry about how long and what direction.

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For the most part most of the pushing is going to be done by kind of right about in here.

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Whatever I've done at that point actually it's probably even a little bit higher but whatever I've done at that point my next goal is just to take advantage of that and train as much as I can to the club.

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What we teach in the stocks full swing will give you some of the best.

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Mass versus pressure versus ground force relationships and ultimately that's how we're able to build some of this consistency into this complicated thing we call it also.

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Also from a practical standpoint I tend to think that the more important one is not so much how well I push with that trail leg but more so.

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How well do I keep this relationship in the frontal plane and be able to push with that lead leg so if I get totally on top of the golf ball like this then when I push it's going to have a hard time creating side bend out of it that's going to make it hard for me to have a real shallow angle of attack especially with the longer clubs.

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So if you're focusing on kind of that feeling of pushing through the ground I would focus on that one there which is the bracing of that lead leg to help trigger the whole release.

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Look something like that.