Your chest muscles swell the same amount after a hard workout whether you use a machine, barbell, or dumbbells—so the muscle-building stress is about the same.

How much total weight you lift matters more for muscle damage than whether you use a barbell or dumbbells—even if one feels harder or heavier per rep.

When trained men do different types of chest presses—using a machine, barbell, or dumbbells—their chest muscles and shoulder strength bounce back at about the same rate after a tough workout, no matter how stable the equipment is.

After nine weeks of lifting weights—whether heavy or light—men who work out casually don’t get bigger pectoral muscles, even though other muscles in their body do grow. This might mean some muscles just don’t respond the same way, or maybe they’re not doing the exercises right.

If you do push-ups or bench presses with light weights until you can't do another rep, twice a week for two months, your arms and chest will grow just as much — so push-ups can be just as good as gym machines for building muscle, if you push yourself just as hard.

If you lift weights until you can’t do another rep—whether you use heavy weights or light ones—you’ll end up with about the same muscle growth after nine weeks, as long as you’re putting in the same effort and number of reps.