Note the arrow pointing to the cupped wrist at the top of the swing.  Deadly! This overswinging causes the clubface  to be in an "open" position which in  turns leads to terrible slices and pulls. It allows the club head to "droop" which is the beginning of the "over the top"
 move. The "over the top" move leads to high, weak shots or dead left pulls that have little distance, no accuracy and certainly no trajectory. 
This is the result of the cupped wrist at the top. A total breakdown of the angle which generates the power & accuracy of your golf shot. This position turns a 5 Iron into a 9 Iron and makes for very frustrating golf. Do you tend to hit your longer irons the same distance as the mid-irons? If so, here is the
reason. Even though you are swinging harder at the ball with the longer clubs, you are effectively increasing the loft of the club face at impact due to an increased cupped action of the wrist that cannot withstand the added centrifugal force of the club head. Result? Longer iron, faster swing, same distance. Sickening.
  Fundamentals | Benefits | Shortgame | Comparisons  
   
Wristfirm © 2006
   
  The solution is to get rid of this cupping action. The Wrist Firm does just that. It integrates in your mind what the impact position is supposed to feel like and thus teaching you the 'Feel" that you can more easily duplicate on the course. The Wrist Firm also teaches you the correct wrist position at the top of your swing. Any good instructor will tell you that the easiest way to hit a straight ball is to get on the proper plane with a flat left wrist (for the RH player). This is the most effective way to hit a straight shot since everything will be square throughout the swing. You may of seen some players in the past either cup or bow the left wrist at the top. They are either trying to hit a draw or fade or they have had to do that due to years of being on an upright or flat back swing plane. Wherever they happen to be at the top, even those players have one thing in common. They are Rock Solid Flat at impact with the leading wrist. Keep it simple. Square at address, square at the top and square at impact. Wrist Firm will teach you this feel.