Lie on bench or mat. With hand of upper arm, grasp unilaterally loaded dumbbell; pinkie positioned near weighted side. Bend elbow approximately 90-degrees and place arm on hip or side of waist. Position thumb upward (supinated).
Rotate dumbbell so thumb turns downward (pronation). Return and repeat.
Pad or firm pillow (ball pictured) may be placed between hip and arm. Elevation of elbow allows resistance during initial range of motion. This exercise can also be performed seated by corner of table higher than shoulder height (See Dumbbell Seated Pronation. If unilaterally loaded dumbbell, or "half dumbbell" is not available, grasp conventional dumbbell to one side of handle with thumb against inside surface. Also see Dumbbell Lying Pronation with arm down.