Too much of a swing can be detrimental to your scores - but it is easily fixed.
Many golfers have a problem with overswinging. An overswing is when the club shaft goes beyond the point where it is parallel with the ground at the top of the backswing.
Overswinging is usually a problem because the more moving parts one has -and the further out of position one gets - the more difficult it is to bring the club back to the right place at the right time, let alone do it consistently.
When overswinging, the body and club are out of sync and it will take a series of complex compensations to enable consistent contact. That being said, if you can perform well and with consistency in spite of an overswing then your hand-eye coordination and athletic ability must be John Daly-esque.
The two main causes of an overswing I see are 1) the left arm bends, allowing the club to travel too far at the top of the backswing; and 2) the right elbow folds behind the body.
Both faults are shown above - notice in the picture on the left how the left arm remains straight and the right elbow points directly towards the ground - classic preventatives of an overswing. An overswing can also be caused by a reverse pivot.
So, what can you do to fix your overswing? Trying these three drills below is a good place to start...
Get a band
Using a resistance band can help you gain the feeling of turning to the top of the backswing, keeping width and not overswinging. Place one end of the band under the lead foot and place the other around the grip of your club.
When you turn to the top of your backswing, make sure you keep the tension in the resistance band - it will be extremely difficult to overswing if doing this drill correctly.
By doing this simple drill, not only will it help to prevent an overswing, it will help to build a more compact and more powerful golf swing.
Fix left thumb
Don't over stretch your glove thumb down the shaft when taking your grip, as this is likely to permit an overswing. Try and shorten your thumb to give yourself more control.
Left foot down
Keep your left heel grounded during the backswing and prevent the left knee from sliding laterally in your quest to solve your overswing.