Upper arms drop below parallel on the extension
Gravity assists the movement; the lateral head is not fully loaded.
Overactive muscles
Latissimus dorsiPosterior deltoid
Corrective work
Foam RollLats↗StretchLat stretch (kneeling overhead)↗Gravity assists the movement; the lateral head is not fully loaded.
Loss of the hinge position changes the line of pull and the tricep load.