The link between body rotation and arm movement in the golf swing is often referred to as “sequence of motion.” To me, this is one of the biggest keys to better golf but too often ignored in instruction.
In 1946, Percy Boomer wrote “On Leaning Golf,” a book in which he referred to the backswing as a race between body rotation and arm swing. He said that whatever wins the race away from the ball will win the race to the top of the backswing and whatever wins the race to the top will win the race starting the downswing. Boomer went on to write that good players allow their bodies to win that race while most amateurs let their arms take over too much. This definition of sequence of motion is the best I've seen.
More than 60 years later, a Golf Digest story said that by the time the left arm reaches waist high in the backswing the average tour player's shoulders have rotated 50 degrees and the average amateur's between 15 and 30 degrees. This verifies what Boomer stated – that great golfers rotate much earlier with their torso than amateurs, which gives them the proper sequence and allows their body to lead the downswing.
With a fuller body turn and shorter arm swing, a tour player doesn't have to get his driver's clubhead to parallel on the backswing in order to launch 300-yard drives. That's because their towering shots are the result of a full body turn.
Kip Putterbaugh operates the Aviara Golf Academy in Carlsbad.