Upper Body Unit.
During the back swing movement you must
hold the elbows as close together as is physically possible, the
right elbow tucked against the waist and the biceps of both arm
must be held against the chest cavity thus holding the upper body
unit firmly together as a very compact unit.
(This applies during the back swing and the down swing movements.)
However as you make the back swing movement,
you must focus on the left shoulder/arm to push the compact upper body
unit to the end of the back swing movement.
( You must keep the right arm
in a firm but passive condition throughout the back swing movement.)
During
the down swing movement, as the hip movement force the passive
compact upper body unit to rotate around the central core of the
spine, it is important to understand that whilst hip movement forces the upper body unit to
rotate into the down swing movement you have to focus on the left shoulder as the dominant element.
When the club head makes contact with the ball the right arm is quickly forced into the fully straightened position -- whilst the whole
body turns to fully face the target area.
(Top class golfers physically
force the right arm into the fully straightened position but for
now simply allow this happen automatically.)
LOWER BODY
During the back swing movement the lower part of the body
resists the rotational movement of the compact upper body movement.
However during the down swing movement it is the left leg
and the left hip that force the hips to rotate towards the target
area thus forcing the compact upper body unit to rotate around
the central core of the spine whilst the left arm remain held close to the right shoulder.