ExRx.net

Why is the anterior deltoid not a synergist in the lever seated fly when it is a synergist in all other fly-like exercises?

exrxDOTnet/WeightExercises/PectoralSternal/LVSeatedFly.html

Anterior Deltoid is only a weak synergist during transverse flexion but not transverse adduction, meaning the shoulders need to be internally rotated. See comments under Anterior Deltoid (http://exrx.net/Muscles/DeltoidAnterior.html" onclick="window.open(this.href);return false;) and differences between these two movements: http://exrx.net/Articulations/Shoulder.html#Transverse" onclick="window.open(this.href);return false;

"Anterior Deltoid is only a weak synergist during transverse flexion but not transverse adduction, meaning the shoulders need to be internally rotated."

Thank you for the reply!

Do you mean the anterior deltoid is a weak synergist during transverse adduction but not transverse flexion? Shoulders are internally rotated during transverse flexion.

With the lever seated fly, the shoulders are internally rotated, so why is the anterior deltoid not listed as a synergist? It's only with the lever pec deck fly that the shoulders are externally rotated.

Another, related question ...

Why do you recommend internal shoulder rotation during the lever seated fly and dumbbell fly? I thought it was to better isolate the pectoralis major; however, according to what you're saying right now, and according to Wikipedia's Chest Fly page, if you internally rotate your shoulders, your anterior deltoids get more involved.

Why recommend internal shoulder rotation during these chest exercises if it reduces emphasis on the pecs by bringing in the anterior deltoid?

Sorry if that's a stupid question! I'm just trying to understand the reasoning behind the instructions on this website, which I have to say is currently one my favorites.

What an amazing resource!

By the way, I couldn't quote you using the quote button because your username is a URL, and I am not authorized to post URLs!

fluoresce wrote:Why is the anterior deltoid not a synergist in the lever seated fly when it is a synergist in all other fly-like exercises?

exrxDOTnet/WeightExercises/PectoralSternal/LVSeatedFly.html

Good info thanks for sharing it.

The exercise you cited does show the front delt as a synergest; it's listed third as a synergest: http://exrx.net/WeightExercises/Pectora ... edFly.html. Perhaps you were referring to when the exercise is performed on a pec deck machine http://exrx.net/WeightExercises/Pectora ... eckFly.html? In that case, the arm is positioned with the shoulder externally rotated so the front delt no longer has a line of pull to be engaged. Even with the shoulder internally rotated as with the lever fly you had cited, the front delt is a weak synergest in strict transverse flexion.

The explanation to the discrepancy for the pec dec version can be found in the second sentence under the comment section of the Anterior Deltoid page:
http://exrx.net/Muscles/DeltoidAnterior.html