Grasp a dumbbell with your left hand. Put your right hand and your right knee on a flat bench to place your torso in parallel with the floor.
Place your left upper arm along your torso, parallel to the floor, and keep it in this position throughout the exercise. Allow your left forearm to hang down under the weight of the dumbbell, with your palm facing inward.
Slowly straighten your left arm. Hold this position for a moment, then slowly return to the starting position.