Getting the club shaft to shallow 'onto plane' in transition is a huge topic in modern coaching.
A high percentage of golfers will suffer with an 'over the top' top move that swings the club down and across the ball. This isn't fixed by dragging the hands down but by understanding how to 'shallow the shaft' in transition.
This video comes from my 'Modern Golf Swing' course, 'Side-on Mechanics' where I elaborate much more on the topic but for now, let's just say that when the club is on plane early in the downswing (and the clubface is strong) then the player can move freely through ball and take advantage of a host of benefits that all add up to further, straighter shots.
Although there are a number of factors involved in shallowing the shaft in transition, there is no stronger influence than the direction that the hands move in.
Even with an outward movement of the hands you still need to allow the right shoulder to rotate externally and forearms to rotate. If you are gripping the club excessively tight and thus, resisting the shallowing motion then, of course, you are just going to create an over the top pattern instead.
Equally, if you are in a hurry to turn your upper body as you start your downswing then the shaft won't be able to shallow.
I think this video of Cameron Champ in his even younger days is incredible. Notice how the hands work out toward the ball right in the onset of transition and then they continue to travel out in the direction of the ball until just before impact. This is how you can rotate very hard and keep the clubhead behind you.
In this course I take you step by step through a process of learning the key moves to a modern golf swing. Hand path and shallowing the shaft are part of it but you need to understand the full movement pattern if you are going to develop a powerful modern golf swing.
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