Weight Forward - Using SwingCatalyst and SAM Balance Lab to Explain Pressure Throughout the Swing

[william1943]

http://www.clubmakerscalculator.com/golfbiomechanics/weight-shift-in-the-golf-swing-clearing-the-mass-confusion/#_edn1

Here is a nice discussion of the things being presented here with reference to the range of values found when more than 2 golfers are studied. Gives a nice  overall

presentation. Discusses the difference between the center of mass and the center of force.

Another thing of interest ( implied  by the question above regarding toe or heel weighting in this regard) is the DIRECTION of the forces being recorded  on the plates. For example, the force may be 90% on the right foot. Is that force  applied directly in to the ground or perhaps at right angles to the target.? Or some combination of the two.

If I stand only my right leg  and don't move  I will have 100% of my weight applied to the plate  into the ground on the right leg. Now if I try to move left I will apply a force in the opposite direction of this movement and the force will be applied laterally towards the right. In general, the more movement that occurs the more the plate will register a force in the opposite direction of the movement.

Some might  think that a 90% registration of force on the plate suggests that the mass of the body has moved to the direction of the force being recorded. But taking a sprinter as an example, right before the starting gun goes off the sprinter is  not  moving, his  feet  resting on the starting blocks. He is in motionless balance.When  the gun goes off a large force will be recorded  on the starting  block The runner is pushing against that starting block But the mass of this body has not shifted backwards over the starting block . IN this case the force is  applied laterally

anyway from  the direction of movement of the runner.

IN golf, both  movements of  mass ( center of mass)  and  forces   used  create  motion  occur simultaneously  and  are being measured by the plates. The only way to distinguish between the two is to  stop  the movement . Then the  forces on the plates will record changes in  center of mass alone.

So, in summary we have

PLates that measure forces ... but we don't  know

a the direction of these forces ( down, forward, backward  left, right)

b  the amount these forces are due to muscles creating MOTION

c the amount these forces are due to shifts in the mass of the body one way or the other.

Another interesting question ( raised in the citation above) is whether the plates record the forces at the same time they are generated .Or is there a  time  lag  between the force

the body applies and the reading recorded by the plates.If there is not perfect fidelity in force recording ,the assumptions made by looking at the swing positions and assuming that they correspond accurately to the force recordings will be misleading.

Maybe Bubba Watson's refusal to take lessons is an intuitive respect for the difficulty in  analyzing   the  golf swing scientifically. .

[iacas]

http://www.clubmakerscalculator.com/golfbiomechanics/weight-shift-in-the-golf-swing-clearing-the-mass-confusion/#_edn1

Here is a nice discussion of the things being presented here with reference to the range of values found when more than 2 golfers are studied. Gives a nice  overall presentation. Discusses the difference between the center of mass and the center of force.

Thanks for sharing the article. I've read it before, but may read it again. Also, @william1943 , we've studied far more than two golfers, though this thread primarily shows two examples. It would have been a rather long (and boring) video to show a few hundred.

The article says the same things we've been saying for years. Particularly, that the COM "lags behind" the COP and doesn't move much outside of about 55% +/- 5%.

Another thing of interest ( implied  by the question above regarding toe or heel weighting in this regard) is the DIRECTION of the forces being recorded  on the plates. For example, the force may be 90% on the right foot. Is that force  applied directly in to the ground or perhaps at right angles to the target.? Or some combination of the two.

Any time the force is slightly angled (shear forces), the direction of the force can be demonstrated at an angle. Forces exist in three dimensions. The target is in one plane, so perpendicular has little meaning here - it could mean purely vertical (directly into the ground) or purely horizontal - both are "right angles to the target."

We typically see that forces are applied primarily downward (vertically), but shear forces (horizontally in "both directions" (toward/away from ball, toward/away from target)) are present as well.

If I stand only my right leg  and don't move  I will have 100% of my weight applied to the plate  into the ground on the right leg. Now if I try to move left I will apply a force in the opposite direction of this movement and the force will be applied laterally towards the right. In general, the more movement that occurs the more the plate will register a force in the opposite direction of the movement.

In your example, yes. But obviously not always. In the golf swing, the percentage of force AND the percentage of mass shift right, then shift left, for large chunks of the backswing and downswing.

Forces applied downward are shown as a GRF in the opposite direction. They mirror each other; since the ground doesn't move (much), any force we apply to it basically ends up moving US, which is why most of the time you see GRF drawn something like this:

Shown here are really rough approximations of the GRF (it's shown in 2D, but that's enough to see both vertical and shear forces along the target line) with the blue arrow, the COM with the blue dot, and the moment arm with the red line.

Some might think that a 90% registration of force on the plate suggests that the mass of the body has moved to the direction of the force being recorded. But taking a sprinter as an example, right before the starting gun goes off the sprinter is  not  moving, his  feet  resting on the starting blocks. He is in motionless balance.When  the gun goes off a large force will be recorded  on the starting  block The runner is pushing against that starting block But the mass of this body has not shifted backwards over the starting block . IN this case the force is  applied laterally anyway from  the direction of movement of the runner.

Yes, but doesn't that go without saying at this point? A sprinter also has, at that point in time, his COM well in front of his feet. If he didn't apply any upward force at all… he'd not win very many races as he'd face-plant about five feet off the starting blocks with a nasty case of road rash. Gravity is still in play, of course.

Since by definition involves the use of one foot on the ground at a time, and is perpetually the act of catching yourself before you fall and propelling yourself forward once again, with each stride, it's fine for background understanding but does not apply very much to the golf swing, which is fairly stationary and almost always with two feet on the ground.

IN golf, both  movements of  mass ( center of mass)  and  forces   used  create  motion  occur simultaneously  and  are being measured by the plates. The only way to distinguish between the two is to  stop  the movement . Then the  forces on the plates will record changes in  center of mass alone.

Yes, that's been said here several times - you cannot measure COM in a dynamic (moving) system. Not unless you know the masses and distribution of those masses on a body. There are some reasonable approximations out there, or you can measure each person's individual parts, but it's time intensive and often unnecessary.

So, in summary we have PLates that measure forces ... but we don't  know

a the direction of these forces ( down, forward, backward  left, right)

b  the amount these forces are due to muscles creating MOTION

c the amount these forces are due to shifts in the mass of the body one way or the other.

I don't agree with any of those:

1. We can know the direction of these forces.
2. We can know the amount of forces due to muscles because… the only other force acting on a golfer during a swing is gravity. Everything else is created by the muscles (which create motion).
3. Also wrong - we can map the segments of people's bodies and know where their COM is at any given point in time, and mapping that against the COP and the GRF, determine things like the moment arm and thus the torque, etc.

Another interesting question ( raised in the citation above) is whether the plates record the forces at the same time they are generated .Or is there a  time  lag  between the force the body applies and the reading recorded by the plates.If there is not perfect fidelity in force recording ,the assumptions made by looking at the swing positions and assuming that they correspond accurately to the force recordings will be misleading.

The delay is incredibly small (rates at which electricity travels, basically), and can be accounted for in the software.

The S&T; DVDs (see here: ) did not properly sync their video with the pressure plates, though, and horrible results were generated. So yes, it's possible to screw it up… just as it's possible to get the timing down to such a negligible amount it's just that - negligible.

Maybe Bubba Watson's refusal to take lessons is an intuitive respect for the difficulty in  analyzing   the  golf swing scientifically. .

Or not.

[golfrocks]

some Teachers say that for driver you should be more on your back foot at impact to hit up….. do u think this is true?

[Phil McGleno]

@william1943 what was the point of your post?-Are you arguing? Agreeing?-Just sharing stuff?

[iacas]

some Teachers say that for driver you should be more on your back foot at impact to hit up….. do u think this is true?

It's not necessarily true for all, but it is for most. The driver doesn't require golfers to hit the ball off the ground (i.e. with a club traveling downward).

But please be careful about the terminology. I prefer a student still have weight (mass) and definitely pressure (force) forward (the mass not nearly as much, even 50/50 can be okay, rarely is 55% right okay) over having more mass (weight) over their back foot.

Appearances can be deceiving:

These lines are roughly mid-way between the feet:

[william1943]

Sharing.    I think , however( since  you asked), that, ( and this is just my opinion)  if you don't have a plate to measure your forces  you may erroneously conclude that it should  feel like

you are shifting your weight to your right foot on the backswing. I think that is dangerous. I think it is much better to "feel"  like you are maintaining your balance  50 50 during the swing. The plate may say 90% on the right foot but the swing should still feel like your are balanced. If you are balanced you can move more easily and faster to the left toward the target than if you start the downswing with most of  your weight feeling like it is on the right foot.  I know a  lot of golf instruction says move to the right. I think this is the worst

possible  advice  you  can get.

I even try to move my lower body a tinny bit left during the backswing  to compensate for the mass of the club club and arms going back. The weight moves toward the target on the on  the downswing of course. Moving the weight to the right is something I see very few good golfers doing if i watch U tube of their swings  carefully. And  if they do move it to the right (Henrik Stenson does this these days a little in my opinion), they  do it early in the backswing and then quickly reverse direction at the transition or even before. The worst thing you can do is hit the ball with the weight on the right foot. The weight must be moving toward the target during the strike. That is why the divot is taken after the ball is  hit.

I  have not won the US Open so this is just my opinion.SO I won't argue with anyone who feels differently.  I could be wrong. Golf  is a journey. It beats working even if you are going in the wrong  direction .

[iacas]

You may have been responding to Phil or me, I don't know, but I'll respond and of course anyone else can as well.

Sharing.    I think , however( since  you asked), that, ( and this is just my opinion)  if you don't have a plate to measure your forces  you may erroneously conclude that it should  feel like

you are shifting your weight to your right foot on the backswing. I think that is dangerous. I think it is much better to "feel"  like you are maintaining your balance  50 50 during the swing.

I disagree only in that feels vary from player to player. In trying to get players to make the same mechanical change (from swaying their hips back and not turning them much to turning them more in place), I've had players tell me:

• It feels like they're loading into their right side more.
• It feels like they're staying on their left side more.
• It feels the same as far as weight but that they're turning more.

Feels aren't real. I don't teach anything based on feels, I teach 100% based on mechanics. The rub in that is that I teach the mechanics by finding the feels that correlate to the player to produce the proper mechanics . More on that here: .

I agree that in many good players the mass doesn't move back much during the backswing, but how that feels to different people varies quite a bit.

The plate may say 90% on the right foot but the swing should still feel like your are balanced.

a) the plate will rarely say 90% right in a good swing unless you're a lefty and you're talking about some time around impact.

b) You can remain balanced, by the definition, by keeping your COM inside the other edges of your feet. Only when it's outside of that range are you going to fall over. I take it you mean close to 50/50, and generally, as I've said, I agree, though we do see mass anywhere from 50-60% right at the top of the backswing in very good right-handed golfers.

I know a  lot of golf instruction says move to the right. I think this is the worst possible  advice  you  can get.

I think we tend to agree a lot more on that than we would disagree.

I even try to move my lower body a tinny bit left during the backswing  to compensate for the mass of the club club and arms going back.

Maybe you do, maybe you don't. The club weighs very, very little, though, and if your MASS actually shifts left, it's probably not ideal either. Though, if you have a hard time going from a little right to a medium amount left by impact, there are far worse things than cheating forward a little bit.

Moving the weight to the right is something I see very few good golfers doing if i watch U tube of their swings  carefully.

Virtually all good golfers shift their weight (mass) slightly (I said slightly ) to the right during the backswing. Grant Waite had more weight right than left at the top of his backswing.

The worst thing you can do is hit the ball with the weight on the right foot. The weight must be moving toward the target during the strike. That is why the divot is taken after the ball is  hit.

No real argument there, except of course that there's more to it than just that for clean contact, but… yes, off the ground it's very difficult to hit the ball solidly if your weight and force are on the trail foot.

[iacas]

Good video overall. Two small quibbles would be that I would say 80/20 is on the high end on the backswing, and the low end at impact (assuming a player is hitting an iron and not a driver).

[william1943]

I think the  mass of the body if measured at rest should remain 50:50 throughout the golf swing  up till impact. Then it moves forward.

The plate  forces are measuring a reaction to the swinging of the club. The club moves back. The right leg resists the arms and club and shoulders  moving back  to maintain 50:50  mass ( at rest)   balance

So the faster you swing back,the heavier the club you are using, the greater the force will be seen on the right foot at the beginning of the downswing. AT the very beginning

of the downswing, the arms and the club head move backward even more ( away from the target). This change of direction is a force directed backwards and so

it must of countered by the  right leg pressing in to the ground to keep the mass of the body  centered and the axis of the body rotation  stable.

(As in an ice skater spinning around. The center axis of oration must be kept still\ or the speed slows.) It is a good idea at the beginning of  the downswing to feel the pressure

move to the left foot. This means you are  balancing  the backward  mass and thrust of the early downswing motion with a slight counterbalancing move to the left foot.

This is the key to the golfswing: Understanding that the transition has a force moving backwards ( arms and club) and  a counter force moving forward with the hip moving to

target  simultaneously to counter the backward initial thrust of the downswing.  Once the club changes direction  and starts  moving forward  halfway through the downswing

the backward force is released and the club  thrusts forward. This release of the initial backward force of the downswing  is what causes the "release" of the club through the ball.

If  the pressure plates seem to suggest that the pressure is too high early in the downswing this could have a number of causes.

1. The golfer swayed on the backswing and moved his body mass off center, needing to correct it  before the downswing starts.

2.  The golfer is trying to swing too  hard at the start of the backswing, so he must counter that force as explained above.

3. The golfer is a power hitter and needs this much counter force  to stay balanced .In this case the shot will be ok. No need to worry .

It is essential to understand that the pressures  generated by the feet  in a golf swing are a reaction to the swinging of the arms  and the club . By them selves , achieving

the"correct pressure"  readings will accomplish nothing. When you separate  the foot pressures from the arm swing you become a dancer not golfer.

Seve Ballesteros had a concept he taught where he imagined his feet glued to two railroad tracts. That kept him balanced . No dancing. Swing with your arms and shoulders.

Use your feet to stay balanced while swinging. Focusing on generating a lot of  pressure in the right leg in the backswing and the left leg in the  downswing tends to

disrupt the more essential task of staying balanced.

WR

[iacas]

I think the  mass of the body if measured at rest should remain 50:50 throughout the golf swing  up till impact. Then it moves forward.

That's not consistent with what we've found at all. It starts out somewhere between 50/50 and 40/60 (forward) at address. Throughout the backswing some weight moves to the trail side. At impact as the hips have slid forward some weight is on the front foot already.

The plate  forces are measuring a reaction to the swinging of the club. The club moves back. The right leg resists the arms and club and shoulders  moving back  to maintain 50:50  mass ( at rest)   balance

No, that's inconsistent with what we know to be the case in the best players.

So the faster you swing back,the heavier the club you are using, the greater the force will be seen on the right foot at the beginning of the downswing.

The weight of the club is nearly insignificant in this. 300g is only about 2/3 of 1 pound. Your hands weigh more than your driver.

It is essential to understand that the pressures  generated by the feet  in a golf swing are a reaction to the swinging of the arms  and the club . By them selves , achieving

the"correct pressure"  readings will accomplish nothing. When you separate  the foot pressures from the arm swing you become a dancer not golfer.

No, the action of the body (without even swinging a club or your arms back) can generate forces and torques as well.

Let's stick to actual science and reality instead of imagined feels and mental pictures.

[Stretch]

Foley talking about changes Justin Rose has made to his pressure shift and the results.