When we look at what happens to the golf club during the swing it is hard to separate the action of the club from the action of the player’s body.  It is difficult since the club is acting in response to torques placed on it by the body, and the club likewise places torques on the body.

The club may have five different torques acting upon it.  The arms of the golfer exert a torque on the club which gives it an accelerated rotational motion about the axis of the swing.  The wrists, under the control of the golfer, may exert a torque on the club which may accelerate the uncocking motion of the wrists.  The centrifugal torque experienced by the club, when looked at in the rotating system, also accelerates the uncocking process.  The fourth torque is that which comes from the force of gravity acting on the club.  The fifth torque is that which results from the acceleration by the golfer of the center of rotation in his shift toward the target.

If we use the example of a professional golfer with a driver swing speed of 109 miles per hour, in the first 10^th of a second (.10) the club is accelerated to 20 miles per hour.  At .20 seconds the club is traveling over 75 miles per hour.  At .33 seconds with a speed of 109 mph impact has taken place. The downswing has lasted just over a third of a second.

For the first .10 second the club speed increases in a somewhat straight line of ever increasing acceleration.  Then as the wrists uncock, there is an increase in the rate of acceleration of the club, then the rate of acceleration falls off slightly toward the end of the downswing. 

After .10 second into the swing when the wrists are relaxed, the club is swinging out to hit the ball from the action of the centrifugal torque in the rotating system.  The slow down in acceleration at the end of the downswing shows that the arms and hands of the golfer are slowing down as the clubhead approaches the ball.  The rotation of the club in the plane of the swing produces a force by the club on the golfer’s hands that slow the hands even when the golfer is trying to move them with ever increasing speed.

The acceleration of gravity on the club is a little over 8% of the total clubhead speed produced.  The forward shift of the golfer toward the target may comprise as much as 8 to 8.5% of the speed at impact with the ball.

At the beginning of the downswing the shaft of the club bends to leave the clubhead behind. This is a natural effect; the shaft bends as it does because it must exert a force on the clubhead to make it move (produce acceleration).  The shaft becomes straight at about .29 seconds into the downswing; the club is about horizontal at this time.  The shaft then bends toward the target in ever increasing amounts until ball strike.  There is a blip which appears from about .16 seconds to .23 seconds.  This blip will take some explaining.

When a shaft which is clamped at the butt (grip end) is defected (drawn back and released) it will move back to straight continue in the opposite direction losing speed but gaining energy then stop and return back to center and begin slowing down, but gaining energy.  This action is similar to a pendulum except the top end is solidly attached.  If the shaft flex is correct for the speed of the golfer’s swing, the time it takes for the club to complete 1 ½ oscillations is the exact time of the golf swing.

As the downswing begins the club moves from straight to bending backwards acquiring energy as it bends.  Then during the downswing the shaft unloads, becomes straight, and loads again in the opposite sense bending forward in the swing.  As the swing progresses the shaft unloads, becomes straight, loads again bending backward in the swing, then unloads once more before the ball is hit.  If you are counting that is 1 ½ oscillations.  The hands tend to take away or reduce the frequency of the oscillation of the shaft at a point of .135 seconds into the downswing.  This reduces the amount of unloading and loading taking place in the middle of the downswing.

The flexing of the shaft contributes about 3% to the clubhead speed at the ball, and that is assuming the flex is close to the need of the golfer.

What does all this mean to the average golfer?  Well, what the club does in the downswing is quite complex and can be influenced by torques applied from many different body movements.  No one golfer is the same as any other golfer.  If you want to play golf clubs that fit your particular swing you must be fitted by a clubfitter who has the knowledge and equipment to evaluate your needs.   He can then provide you with the specifications for golf club characteristics that will fit your swing. 

If you wish to play your best, you must have clubs which are fitted to your swing.