The #4 Pressure Point -- where the Left Arm contacts the side of the chest -- is the first stage of the Swinger's Three Stage Rocket. It is the Pivot (specifically the Right Shoulder Turn Thrust) driving the Left Arm and Club during the Start Down and Downstroke. That Pressure rapidly subsides as Stage Two (the Left Wrist Uncock) and Stage Three (the Left Hand Roll) take over and complete the Release Sequence.
The point here is that the Right Shoulder does not (normally) drive the Lever Assembly through Impact. It is just too slow, and the Hand Action Accumulators (Uncock and Roll) are much more efficient. Continuous Shoulder Turn Pressure is an action that, according to Homer Kelley, "might be useFul for a plowhorse", but it is not the ideal for a golfer.
Green-genes . . . Great post. Fog lifting on #4 PP for me. Could we go a bit deeper here?
What Pressure Points are you aware of in regards to the strongest sensation in your Swinging Motion?