Golf Swing Physics

3+. Video Examples

Guest article by Rod White -- December 2008

In this section we’ll look at slow motion videos of some professional golf swings.

The real golf swing is more like a triple pendulum with the ‘beam’ between the neck and the shoulder forming the third arm of the pendulum. While watching the videos, remember the essence of a good golf swing is the reverse of the ice skater effect – the transfer of energy with unfolding. The total power produced by the golfer (about 2.5 kW for a professional) comes from the biggest muscles in the body – the upper legs and torso. The problem is how to transfer this power, from the muscles, through the shoulders, arms, club, and eventually, to the ball.

The backswing

consists of a large shoulder rotation against the hips to pretension the muscles of the torso.
minimises the moment of inertia of the arms and the club by folding the left arm against the shoulders and cocking the wrists. In all cases the down swing begins with the left arm folded almost parallel with the shoulders, and the club typically cocked to 90 degrees.

The downswing movement

leads with the large muscles of the legs and torso rotating and building momentum in the hips, with
the whole folded system -- the upper body, shoulders, arms and club -- moving almost as one.
Once the rotation is firmly established, the arms swing out – transferring energy from the body to the arms,
then the club swings out, transferring energy to the club.

Tiger Woods

Tiger's swing is the swing closest to the ‘textbook swing’ of the golfers here. Things to note:

The long extended backswing to create a large shoulder turn and tension in the muscles of the torso.
The system stays "folded" through the early part of the downswing.
Excellent retention of wrist angle well into the downswing.
Hands slow noticeably as he approaches impact. This is not "deceleration" in the golf instructor's [negative] sense; it is caused by the tension in the shaft exceeding the shoulder torque, and is evidence of the transfer of energy from the arms to the clubhead.
Hand, wrist, and forearm strength are not a factor here -- except to be able to stay relaxed with the large shaft tension trying to yank the club from his hands. And the same comment applies to the other videos as well.

Sergio Garcia

Sergio is not as tall as many pro golfers, so to hit the ball as far as he does he must have a more efficient swing. The distinguishing feature here is the large wristcock midway through the down swing. Things to note:

Even more shoulder turn than Tiger.
As he starts the downswing, he actually increases his wrist cock angle. This "early release" of the club means that he's not using sufficient positive wrist torque to maintain even a 90º angle.
Midway through the swing, the wrist cock is probably well under 60º, so that work done during this part of the swing is transferred more efficiently to the club when the wrists unfold.

That is where his exceptional clubhead speed comes from.

Freddy Couples

Fred has one of the most admired swings in the game, superficially an easy swing, but he’s actually doing a lot of work very early. The important thing to note here is how Fred starts his downswing. At the top, his whole body is coiled, including his hips. His first move is a big rotation of the hips. Everything above the hips turns, but only because the hips are turning. Everything above the hips -- torso, shoulders, arms, and club -- are almost frozen, and just move with the hips. That is what we mean by "staying folded". The rest is pure swing -- no hands.

Of course Fred, like Tiger and Sergio, keeps his wrists cocked until very late in the downswing.

Jamie Sadlowski

Jamie is not a household name for most golf fans -- unless they are fans of long driving. Jamie, at only 165 pounds, has been the world champion of this sport for the past two years (2008 and 2009) with record drives exceeding 400 yards. How does he get the clubhead speed to accomplish this against much bigger, more-muscled competitors?

Jamie is an incredible athlete with extreme flexibility, and none of us could hope to reproduce this swing. But because the downswing is so long, it shows very clearly the ideal of staying folded.

As a long driver, all of his actions exceed those of PGA tour golfers: an incredible shoulder turn and even more incredible wrist cock. He also has the advantage of a long shaft on the driver (see next section on technology).

Many people have trouble believing that you do not need to use wrist torque to have an effective golf swing. But there are some good examples from outside golf illustrating this point.

Perhaps the best example is the trebuchet, a medieval siege machine used to fling rocks a long way. YouTube has many videos of trebuchets. Let's see what we can learn from them:

Let's start with a good overview of a working trebuchet from DGseward.

The raised weight represents the torque applied through the shoulders,
the long wooden beam represents the golfers arm,
and the rope sling represents the shaft of the golf club.

Think about it; if the club had a perfectly flexible shaft -- like the rope sling of a trebuchet -- then there is no way to apply wrist torque to get any action from the clubhead. Yet the trebuchet was a very effective siege weapon. It was the best, most powerful catapult in warfare for centuries until it was replaced by gunpowder-powered cannons, demonstrating that "wrist torque" isn't all that important.

Let's turn DGseward's video upside-down to show the similarity to the golf swing. It should look more like a real golf swing this way. The arms accelerate from the turning "shoulders" (the counterweight), and the club (the rope sling) lags until it is whipped outward by the tension in the rope.

Trebuchet competitions remain something of a sport today. Games include distance and target competitions, with "punkin chunkin" being an American championship throwing large pumpkins for maximum distance. Here's a pretty basic "punkin chunkin" trebuchet.

Finally, if you want to experiment with a trebuchet yourself, here's a science kit you could build.

Last modified - Jan 25, 2010