http://AskTheTrainer.com/medicine-ball-workouts.html Remember, you are only as strong as your weakest link. This holds true no matter what your fitness goal is. If your goal is to increase your bench press and your shoulders stabilizers are not up to speed, you shouldn't expect any major gains. Medicine ball pushups on dual balls is a good way to test your shoulder's ability to stabilize. If you can perform 20+ reps with no shaking then you can consider your shoulders stable. If you're shaking all over the place at the start of the set, you're better off ditching bench press for a bit until you can strengthen your shoulder stabilizer muscles. It is even more difficult when you have 2 different sized medicine balls. Important form tip is to lower your chest as far as you possibly can each rep and raise your body up until right before your elbows lock. Personal Trainer Michael Behnken, MS, CSCS http://AskTheTrainer.com