Myth 1 “Keep Your Head Still”
This is one of the most misunderstood myths in golf instruction. Yes, most fundamentally sound golfers maintain a certain degree of stability in their neck and head during the swing, but locking them in place, which many recreational golfers attempt to do, is a big mistake.
In fact, the head should move laterally in the backswing (away from the target) and then toward the target in the downswing. If you lock your head in place during the backswing, a number of bad things can and will happen, including the dreaded reverse pivot. In addition, a severely reduced shoulder turn also is likely to occur, limiting clubhead speed and potential power. A lack of shoulder turn will also tend to cause your hands and arms to become too active, forcing the club straight up and off-plane, instead of around your body. Another bad result of locking your head in place is a dropping of your head, which leads to a change in spine angle and an “off-plane” swing.
By allowing your head to move properly during the downswing, a number of good things can happen. Most importantly, it will encourage a free and complete shoulder turn, creating a dynamic, athletic motion. Also, the shoulders will be able to turn on the proper plane because the spine angle achieved at address will have been maintained. Finally, properly moving your head will reduce the need for excessive hand and arm movement during the swing, increasing accuracy and consistency.
Myth 2 "Keep Your Left Arm Straight"
Like a centred head.a straight left arm is the result of a correct swing,not the cause of one.the biggest killer of a golfer`s game isa reluctance to hinge or cock his wrist`s.The stiffer our forearms,the stiffer ourwrist hinge/cock becomes;it is counter intuitive,but "oily" wrists make you more accurate than rigid wrists.
Solution: Make sure your backswing is a combination of movement shoulder coil and wrist cock.
PGA Golf Professional