Lie with only your head, neck, and shoulder blades in contact with a ball-your lower back should be off of it. Then with your feet shoulder-width apart, push to lift your hips until they're parallel to the floor and your knees are bent at a 90-degree angle. Do standard lying traceps extensions, angling your arms back slightly as you hold the dumbbells overhead, to ensure more work for the long head of your triceps.
