Golfers far and wide want "more lag." But why? And what is "lag"?
If I were to define "lag" it would simply be "the shaft trailing behind the lead arm." You have no lag when you reach what's called an "inline" condition - the shaft is "in line with" the left (lead) arm. The smaller the angle between the shaft and the left arm, the more "lag" you've got.
Lag serves two purposes.
The first is that it helps us to control the low point of the swing. If you flip, your low point is likely too far back. The low point of the swing, for most good golf swings is generally under the left shoulder. Also generally, that's when a good player will "run out of lag" and reach an inline condition with the left arm-shaft. If you lengthen the radius of the left shoulder to the clubhead prematurely, the clubhead will be ascending when it reaches a spot beneath the left shoulder. So the proper timing of that "long radius" to be roughly at low point is important.
The second is both the aid to acceleration and the instantaneous speed achieved by delaying lag as long as possible. I'l talk briefly about both.
The first is simply this. Imagine a golf swing in which the shaft simply stayed inline with the left arm. Imagine moving your left arm across your chest or rotating your entire chest in a circle with in this sort of fashion. Now imagine taping your driver or sand wedge so that the clubhead was by your shoulder and the grip was taped to your hand. You can imagine how swinging your left arm across your chest or spinning your torso (or in terms of the golf swing, doing both at the same time) would be faster because the mass is located closer to the center of the circle. So that's one way in which lag helps - you can accelerate from the top of the backswing more with "more lag" (as defined, again, by the angle between the left arm and shaft).
The second way lag helps with clubhead speed is that you're able to snap the clubhead down quickly just before impact, resulting in near instantaneous speed. You can look up the "small pulley" stuff in TGM if you'd like, but consider a ball on a string. If you grab one end of the string with a ball or a rock on the other end, and you want to get the ball moving as quickly as possible, you don't swing your arm around your body in big circles. You swing it in small, tight circles. These tight circles result in a higher linear velocity than big, slow circles.
The problem is that the latter can be tough to time. Sergio Garcia is a good example of the latter - he employs more of a "snap" release. But Jason Zuback has a "sweep" release and hits the ball just fine. I won't get into the differences there, but will point out that both are highly effective.
The one commonality? All good golf swings have some lag until impact or slightly after impact, particularly on shots struck from the ground (you can flip just slightly with the driver since low point can be behind the golf ball).
- Too much lag is almost worse than too little.
- It's not so much how much lag you've got, it's when you cease to have any that matters.