Position yourself for this exercise by sitting down on a flat bench with a dumbbell in between your legs. Your legs should be spread with your knees bent and feet planted firmly on the floor. Use one arm to pick up the dumbbell, placing the back of that arm against the inside of your inner thigh. Rotate your wrist until your palm is facing away from the inner thigh. Ensure that your arm is completely straight and hanging. In order to execute the exercise, curl the weight forward as you contract the bicep muscles. Throughout the motion, only your forearm should move (your upper arm, legs, and torso should remain completely stationary). Continue the movement until your bicep is fully contracted (when the dumbbell is at approximately shoulder level). Pause briefly at this peak contraction before slowly lowering the dumbbell back to the starting position. Repeat for the prescribed number of repetitions. Switch arms and repeat.