Stability-Ball Prone Alternating Rear Delt Fly

Lie face down with your hips on top of a stability ball and your legs extended behind you and spaced wide for support. Hold a set of dumbbells with your palms facing inward and your arms extended straight down from your shoulders so the weights rest on the floor. Using one arm at a time, drive your elbow up and back and pull your shoulder blade in toward your spine to pull the dumbbell up toward your flank. Lower to the start and continue, alternating sides.