Trunk leans back to swing the dumbbells up
Erectors generate momentum; anterior delt is underloaded.
Overactive muscles
Erector spinaeUpper trapezius
Corrective work
Foam RollUpper traps↗StretchLevator scapulae stretch↗Erectors generate momentum; anterior delt is underloaded.
Upper trap takes over above the shoulder plane; impingement risk.