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.

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.

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.

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 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.

When guys who lift weights do the incline bench press, the steeper the angle, the more their front shoulder muscles work — especially at 60 degrees, where it's working the hardest.