The problem with most combo exercises is that one of the exercises is usually significantly stronger than the other, so when it comes to selecting a weight you must choose according to the weaker exercise. That means you're shortchanging the stronger exercise and not getting as much out of it. Here's a great combo exercise for pecs that doesn't have that problem.
Dumbbell Flye and Squeeze Press
This combo works particularly well for people that struggle to feel most traditional pressing exercises in their chest.
- Start with the dumbbells pressed together on your chest and do a "squeeze press" on the concentric (lifting portion) where you keep the dumbbells in contact with each other the whole time. This works best with hex dumbbells or Powerblocks, but it'll work just fine with regular dumbbells too. Just make sure to line the dumbbells up with one another so they don't slip.
- From there, lower the weights down by doing a dumbbell flye, making sure to keep a slight bend in your elbows to keep the stress on the chest rather than the shoulders.
This combination allows you to reap the benefits of two great chest-building exercises while enabling you to handle more weight than you'd otherwise be able to use for regular dumbbell flyes. Do them on a slight incline. You'll feel it more in your chest and less in your shoulders.
Stick to sets of 8-12 reps using good controlled form. This makes for a great finishing exercise for your chest after you've done your heavy pressing work.