[metallion]

To make it less dramatical, extensor action is a general medical/anatomical term - sort of. An extensor muscle is a muscle that has has the purpose to open a joint, increasing the angle between the limbs attached. So extersor muscles are used to straighten fingers and straighten legs. In TGM Extensor Action refers to the (deliberate) action performed to increase the angle between the right forearm and upper arm - thus using extensor muscles.

So where does the resulting force end up?

When Hitting the pressure is applied through PP#1 and down the shaft. When Swinging the pressure is applied through PP#3 and down the shaft. In both cases the effect will be the left arm (the primary lever) being extended to straight.

I am not the right person to list all the benefits of EA, but maybe the most obvious ones are:
- Creating width
- Presetting alignments at Impact Fix and make sure we keep the alignments during the swing.

Again in Homers checklist he wants you to make sure about EA in some 9-10 places during the swing.

If there is no Extensor Action we - for example - need hand-eye coordination and manipulation to hit the ball solidly. But if we apply it at setup - and keep it - we "know" we will hit the ball solidly, since the left arm will want to extend at impact anyway.

A few extensor muscles shown here: