Dumbbell Alternating Bench on Swiss Ball

As with a regular dumbbell bench press, get yourself into position with your upper back, shoulders, and head supported by the ball and your feet flat on the ground.  
 
Raise both dumbbells above you. Now, lower one dumbbell to the bottom position and then drive it upward. 
 
As you’re driving the dumbbell up, simultaneously lower the other dumbbell. Like two pistons in a car, your arms should be constantly moving in an alternating fashion.