If you're doing push-ups and your feet are elevated (making it harder), your chest muscles don't work as hard. But if your hands are higher than your feet (like on a bench), your chest has to do more of the work—especially when your body is flat.

If you're a guy who works out, doing push-ups with TRX straps might make your chest muscles work harder than regular push-ups—especially when you're more upright, like on a slight incline.

If you're a guy who works out, doing push-ups with your feet elevated (like on a bench) makes your shoulders, arms, and upper back work way harder than regular or uphill push-ups — the steeper the angle, the harder those muscles have to work.

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 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.