Moving to the top of the backswing, as demonstrated by Julian, is coiling a spring - the support you need to have is just as important as the coil .

You now have to transfer your weight to your right hand side and resist against the motion you are creating

You now extend yourself as you hit the ball - flexibility is a key

It was clear that from only a short session there are certain core muscles that need to work and not all are involved in large movements and not so obvious. There is a serious amount of rotation involved combined with fixing points of your body in specific positions and this requires a great deal of muscular condition to perform to a winning standard.