Rate of Closure Article by Sasho

[iacas]

What is 'rate of closure' and can it help your golf swing?

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Rate of Closure is an emerging term you might have heard in golf instruction. We asked Dr. Sasho Mackenzie to explain what it is.

I think:

• For good players, RoC isn't terribly relevant.
• I have said the same thing about measuring, and like the °/foot measurement instead of RPM or °/sec or anything like that.
• I still think, for amateurs, RoC matters if only because they tie it in so tightly to flipping. The flip/roll is how a lot of amateurs "square" the face (or attempt to), and so it's not so much the RoC that's a problem, but the flipping itself.

RoC also matters for chips and pitches and things where you shouldn't have to time things much, and you shouldn't be trying to "roll the face" over much.

What are y'all's thoughts?

[saevel25]

It would make sense that RoC doesn't matter as much for better players. They have a great foundation to begin with that their intent for the shot can be highly repeatable regardless of RoC. I can see when you have a bad foundation for the golf swing that a higher RoC would produce more volatility. I kinda wonder if amateurs have a higher RoC than PGA tour players? 

[Tepi90]

3 hours ago, saevel25 said:

I kinda wonder if amateurs have a higher RoC than PGA tour players? 

It's really weird this topic pops up now, because this is the excact thing that I am completely changing in my swing at the moment. I had this thought of amateurs having higher RoC than tour players put into my head through some youtube video and it sent me to really bad place of trying to keep the face square to swing plane throught whole swing. I watched Dustin Johson do it and thought, damn that looks good, the fact is I'm no Dustin Johson, can't do it.

This came crystal clear to after doing some really basic math about club heads kilogram force at impact; theres so much mass that the club face rotation has to be automatic, wrists have no chance to fight that force. Then I watched some bandy penalty strikes, a sport that I could hit really well at as a kid, and realised the club can't stay square throughout because it will produce too much resistance with air if pulled square throughtout:

My thought is pros have as much face rotation as amateurs. The diffrence is pros have their axis of clubface rotation in the heel which stays "still", making the rotation add speed and stabilise the club face.

Sorry for bad English and crazy explanation, have to hurry to work. I stress this is purely my thoughts, no bullet proof facts behind this. Will post more about this in my swing thread once I get out to give this concept more testing, the firsts tries in the middle of night at field felt promising.

Edited April 17, 2020 by Tepi90

[billchao]

My guess is a pro’s swing would have a flatter curve than an amateur’s - that is, a pro will have a relatively consistent RoC starting pretty early in the downswing whereas an amateur won’t have enough RoC early and then have to really spike it later in the swing.

[Vinsk]

Seems like a difficult thing to even consciously try to mess with. For those of us who have no natural talent with proper forearm rotation I can see it wrecking havoc. Some people just rotate their forearm and achieve an effective roc if there even a thing. It’s probably more of an issue with what amateurs are doing with their wrists, i.e. flipping as Erik stated.

[iacas]

8 minutes ago, Vinsk said:

Seems like a difficult thing to even consciously try to mess with. For those of us who have no natural talent with proper forearm rotation I can see it wrecking havoc. Some people just rotate their forearm and achieve an effective roc if there even a thing. It’s probably more of an issue with what amateurs are doing with their wrists, i.e. flipping as Erik stated.

Yeah, and if your body pivot stops, the club and forearms will tend to "roll" as they "flip" so it's still going to be something I'll talk about with students… even if it's a little "different" - the actual terms and what they understand them to be, etc.

Good players can hit shots with a lower °/foot, poor players often don't have that ability at all.

[JGus]

My thoughts, I just try to hit the ball, I have enough thoughts in my head, there's not room for anymore.  But probably something I should read.

[Warlock]

From what I've read regarding Dr Sasho MacKenzies, passive club squaring torque concept , there is not much active lead forearm supination (and/or right forearm pronation) torques being applied via the hands to square the clubface close to impact . So if that concept is being applied, isn't the ROC partially dependent on the degree of  'passive torque' and the amount of angular momentum it generates (around the longitudinal axis of the lead arm) as the left wrist ulnar deviates?  The MOI of the 'forearm/club' unit reduces as lead wrist ulnar deviation occurs , and any residual angular momentum (caused by that passive torque) will increase the forearm rotation and overall HTV (Handle Twist Velocity) which in turn will increase the ROC. 

But I have also read Dr Phil Cheetham dissertation where he shows some graphs with a weak relationship between HTV (which has a direct relationship with ROC) and 'Driving Accuracy'. 

 

I'm not sure I've seen any research that compares driving accuracy with increased grip strength (where I assume there is less need rotate the clubface square during the downswing). Although less degrees of club squaring doesn't necessarily mean that the ROC would be smaller at impact.

 

 

Edited December 14, 2020 by Warlock

[Vinsk]

21 hours ago, Warlock said:

From what I've read regarding Dr Sasho MacKenzies, passive club squaring torque concept , there is not much active lead forearm supination (and/or right forearm pronation) torques being applied via the hands to square the clubface close to impact . So if that concept is being applied, isn't the ROC partially dependent on the degree of  'passive torque' and the amount of angular momentum it generates (around the longitudinal axis of the lead arm) as the left wrist ulnar deviates?  The MOI of the 'forearm/club' unit reduces as lead wrist ulnar deviation occurs , and any residual angular momentum (caused by that passive torque) will increase the forearm rotation and overall HTV (Handle Twist Velocity) which in turn will increase the ROC. 

But I have also read Dr Phil Cheetham dissertation where he shows some graphs with a weak relationship between HTV (which has a direct relationship with ROC) and 'Driving Accuracy'. 

 

I'm not sure I've seen any research that compares driving accuracy with increased grip strength (where I assume there is less need rotate the clubface square during the downswing). Although less degrees of club squaring doesn't necessarily mean that the ROC would be smaller at impact.

 

 

😳

[boogielicious]

11 hours ago, Vinsk said:

😳

Its been a while since I’ve done a regression analysis. Those look pretty sketchy to me. The variance looks massive.

[Warlock]

1 hour ago, boogielicious said:

Its been a while since I’ve done a regression analysis. Those look pretty sketchy to me. The variance looks massive.

Maybe no relationship at all !  What criteria is used for  'Driving Accuracy'?  For example , if the golfer misses the fairway by a couple of inches or snap hooks out of bounds are they both deemed a miss?

Dr Phil Cheetham also found other relationships between golfer swing biomechanics and 'Handle Twist Velocity'  (which is directly related to ROC in some formula).

The article is here if your interested.

Dissertation (philcheetham.com)

Edited December 15, 2020 by Warlock

[boogielicious]

13 minutes ago, Warlock said:

Maybe no relationship at all !  What criteria is used for  'Driving Accuracy'?  For example , if the golfer misses the fairway by a couple of inches or snap hooks out of bounds are they both deemed a miss?

Dr Phil Cheetham also found other relationships between golfer swing biomechanics and 'Handle Twist Velocity'  (which is directly related to ROC in some formula).

The article is here if your interested.

Dissertation (philcheetham.com)

It looks to me like a poorly designed experiment. They didn’t block variables as in a proper DoE.

[Warlock]

25 minutes ago, boogielicious said:

It looks to me like a poorly designed experiment. They didn’t block variables as in a proper DoE.

Not sure how you would be able to block a variable in a golf swing but I suspect there was also a limit on his budget to conduct a more detailed investigation.

For example , I think grip strength might affect ROC but not 100% sure. Or maybe the golfer has strong forearms and prefers to use muscular effort to square the clubface rather than some passive torque concept . In Dr Sasho MacKenzies research model he found that switching on a forearm torque generator (if timed correctly) could significantly increase clubhead speed , which in turn could increase ROC.

Also, wouldn't one need a high frequency measuring system to accurately measure ROC just before and after impact (is 240 Hz enough)?

Edited December 15, 2020 by Warlock

[iacas]

He could have had the same golfer(s) make swings and measured their grip pressure, and instructed them to make swings trying to grip the club more lightly and more firmly than they're used to.

Also, ROC will be higher if you measure in degrees/time for higher swingers even if their rate may be the same or lower as measured by degrees/distance.

[Warlock]

10 minutes ago, iacas said:

He could have had the same golfer(s) make swings and measured their grip pressure, and instructed them to make swings trying to grip the club more lightly and more firmly than they're used to.

Also, ROC will be higher if you measure in degrees/time for higher swingers even if their rate may be the same or lower as measured by degrees/distance.

Note sure I understand the different ways that ROC can be measured.

It's defined as 'how fast the face is closing'  so I can assume it must be degrees/sec or radians/sec.  And I suspect it is really only important during 'clubface/ball' impact period although one can assume it doesn't change much for measurements taken a few inches before impact. 

Yet Dr Sasho Mackenzie says the following :

"All else equal, swinging the club faster will result in a higher RoC — what I call the swing speed knob — but you don’t start swinging slower as a result! The amount of lost distance will have a stronger negative effect on your score than any potential gain in accuracy. In my own research, I remove the effect of speed and describe RoC in °/foot. This enables me to compare across golfers or within a golfer who has returned with a difference in clubhead speed."

So has he redefined ROC to be measured 'degrees clubface closure/distance clubface travelled' ?  But it hasn't got the same dimensions as the original definition and I find that confusing.

[Warlock]

Example for CCV or ROC (i'm assuming they are the same unless I'm mistaken).  If Dr Sasho Mackenzie is removing the SPV (angular swing plane velocity) aspect of ROC , then he must be concentrating on the HTV and inclined swing plane angle, but that still has dimensions of degrees/time (or radians/time).

 

Edited December 15, 2020 by Warlock

[boogielicious]

2 hours ago, Warlock said:

Not sure how you would be able to block a variable in a golf swing but I suspect there was also a limit on his budget to conduct a more detailed investigation.

For example , I think grip strength might affect ROC but not 100% sure. Or maybe the golfer has strong forearms and prefers to use muscular effort to square the clubface rather than some passive torque concept . In Dr Sasho MacKenzies research model he found that switching on a forearm torque generator (if timed correctly) could significantly increase clubhead speed , which in turn could increase ROC.

Also, wouldn't one need a high frequency measuring system to accurately measure ROC just before and after impact (is 240 Hz enough)?

In a DoE, blocking a variable means accounting for it in the test design. Example: if daily outside temperature is a variable you cannot control, and the test will take more than one day and you have to do it outside, then you set up the experiment with multiple outside sessions where all the other variables get tested equally each day. Then the analysis can account for the effect of outside temperature on each other variable because you have blocked it. The variance in the data set shown suggests other variables are present. I would have to see the test design and data to see what the issue is.

There is a nerdy stats joke about data plots like that. It’s a scatter plot and anyone can just draw a line through it anyway they want and say, “There’s the trend!”.
 

[iacas]

1 hour ago, Warlock said:

Note sure I understand the different ways that ROC can be measured.

It's defined as 'how fast the face is closing' so I can assume it must be degrees/sec or radians/sec.

You could define it and measure it based on the position of the face one foot before the ball and one foot after the ball.

Otherwise, if you measure it as degrees/time, guys with identical ROC in that measurement will have a higher ROC if they swing faster.

In other words, let's say your face is 15° open before impact and 20° closed after impact (1' each). Another player has the same numbers, but swings 10 MPH slower. His ROC could be seen as the same or lower depending on which measurement you prefer.

SAM PuttLab measures 10cm before and after for its ROC.

 

1 hour ago, Warlock said:

And I suspect it is really only important during 'clubface/ball' impact period

Nobody really measures that during that phase because it would assume an absolutely dead-center (sweet spot) hit and incredibly weird numbers given the duration you're talking about. All of these numbers come over a range of space.

1 hour ago, Warlock said:

"All else equal, swinging the club faster will result in a higher RoC — what I call the swing speed knob — but you don’t start swinging slower as a result!"

I'm not saying to swing slower, just that there should be an accommodation made if you're going to measure rotation/time. Zach Johnson might have a slower ROC than Dustin Johnson but some of that is because he swings slower.

1 hour ago, Warlock said:

"In my own research, I remove the effect of speed and describe RoC in °/foot."

Exactly what I'm saying.

1 hour ago, Warlock said:

So has he redefined ROC to be measured 'degrees clubface closure/distance clubface travelled' ?  But it hasn't got the same dimensions as the original definition and I find that confusing.

What do you find confusing about it?

57 minutes ago, Warlock said:

Example for CCV or ROC (i'm assuming they are the same unless I'm mistaken).  If Dr Sasho Mackenzie is removing the SPV (angular swing plane velocity) aspect of ROC , then he must be concentrating on the HTV and inclined swing plane angle, but that still has dimensions of degrees/time (or radians/time).

I think you're over-complicating it.

Rather than doing it in degrees/time he's doing it in degrees/distance. This removes the difference that could be caused purely by clubhead speed.