I’ve never found a satisfying explanation as to why we’re stronger on the decline compared to the flat bench. One theory I’ve heard is that the rom is shorter, and I had accepted this until I tried the decline bench for myself. It was evident to me anyways that you just feel stronger through the movement. You can also run the comparison with dumbbells, which permit full range of movement, and get a similar result, which demonstrates that it’s not just the rom.
Another (bro)theory is that the pecs are just stronger pushing at a slight downward angle. This was my favored theory for a while.
I was doing dips the other day and thought about how the movement resembles nautilus pullovers in that, from a functional perspective, it involves propelling your bodyweight above a hurdle. For example, if you put a ledge at chest height, one person could clear it using a pullover motion, and the other using the dip motion. Is there a movement halfway between the two where you engage both your lat and your pec muscles? Then I thought to myself, ah, maybe that’s what the decline bench is doing.
The delt pulls the humerus upward, the lats pull the humerus downward, and the tension between the two stabilizes the pressing motion. The angle of the decline removes shoulder involvement, so it should logically increase lat involvement. The lats are generally stronger than the front delt, which could be why people’s decline benches are stronger than their flat benches.
I like this (bro)theory, but it isn’t perfect. You wouldn’t think the lats would be involved that much when you look at the rom of the humerus in the decline press. … But you hear that the decline angle involves the delts less. Why does decline press become stronger if it has less delt engagement than the flat press? If you’re removing a muscle group from the compound it logically stands that the force generated is decreased – unless another muscle group comes in for it.