When you do bench presses on a flat bench vs. a slightly angled one, different parts of your chest muscle get worked more — the lower chest works harder on a flat bench, while the upper chest works harder when the bench is tilted up.

When people do an incline bench press instead of a flat one, the upper part of their chest muscle gets more activated — the electrical signal in the muscle moves upward, showing the incline version works the top of the chest more.

If you're a guy who lifts weights and doing the bench press with a medium-heavy weight, setting the bench at a 30-degree angle might fire up your upper chest muscles the most compared to flatter or steeper angles.

When healthy guys lift weights on flat and slightly angled benches, their chest muscle movement and activation patterns don’t really change — so any differences in how the muscle fires are probably not because of how they’re moving.

If you're a guy who lifts weights and doing bench presses, the flat bench works your chest muscles the most — especially the middle and lower parts — compared to when you use a bench angled upward, especially past 30 degrees.

When guys who work out regularly do a flat bench press with a normal weight, their chest and front shoulder muscles are working just as hard as each other.