I sometimes get a little embarrassed when I share the size of the weights I use. If I’m working out my abs I’ll go as heavy as possible, but if I’m training my upper body I keep it light. My personal set of dumbbells.[/caption] That’s okay, according to a recent studyJournal of Applied Physiology. Whether it’s 3-pounds or 30-pounds, you’ll still be able to get strong and build muscle.