Your patient is holding an elastic tube between both hands i…

Your patient is holding an elastic tube between both hands in front of the body, palms up.  Both elbows are flexed at 90 degrees, with both upper arms held gently against the sides of the patient’s torso.  You instruct the patient to externally rotate the shoulders, at the same time, in this position, then return to the starting position.  This exercise strengthens the: