Hand position for arm extension has no scientific or practical application on muscle group (long, medial, or lateral head)recruitment or isolation. anytime arm extension is performed, the triceps are recruited equally to some extent to perform the motion. It is not the hand postion that affects which head is recriuted or targeted more, but the position of the of the shoulder joint.
not to bump this thread up again, but since the tricep inserts into the olcranon process of the ulna, there is a difference in the positioning of the tricep between pronated and supinated grips.
again, i don’t think this is a very significant factor to consider when designing a training program, but there must be some difference in tricep work between supinated and pronated grips.[/quote]
I agree that shoulder position is much MORE significant of a factor than pronation/supination, but pronation/supination does in fact play a role in which head of the tripeps is used:
Using a reverse grip (supinated) engages more of the medial head of the triceps.
Using the rope (nuetral grip) engages more of the lateral head of the triceps.
In general, the movement targets the triceps and hits the anconeus. If you reverse the grip, you will involve more of the wrist extensors (as stabilizers).