Alternating Flat bench dumb bell press

[Nemesis RR]

Why are flat bench dumbbell presses so much harder than when doing them simultaneously? Is it just a weakness I have?

For reference 50% weaker when doing the exercise alternating

 

[Savagesteve]

I haven't done alternating flat bench dumbells but I like to alternate when shoulder pressing and it seems like I can do more weight. You think your fatiguing more by hold the weight in place while lowering one side at a time?

 

[Leancuisine]

I can do the same weight? But it's a balance and core issue in your case.
I guess I've been heavy into athletics my whole life and have a pretty decently strong core.
Just stick with it and your strength will get there.

 

[Leancuisine]

BTW alternating flat DB is one of my favorite chest.exercises. love them.