For older people, doing four sets of weight exercises instead of just one can help build more muscle—but only if their body is already somewhat responsive to exercise; if it’s not responsive at all, more sets don’t help.

If older people don’t get stronger from doing just one or two sets of weight exercises, doing four sets might help them build more strength—but it doesn’t work as reliably as it does for making muscles bigger.

If you're an older adult who's already seeing some muscle growth from light weight training, doing more sets might help you build even more muscle—but the extra gain isn't big enough to be sure it's real and not just luck.

If you're an older adult who got stronger from light weight training, doing more sets might help you build even more muscle—but we're not as sure about this as we are for people who didn't respond to the light training at all.

If older people don’t get stronger with just one set of weight exercises, doing four sets instead might help them build more strength.

If older people don’t get stronger from doing just one set of weight exercises, doing four sets instead might help them build more strength after training twice a week for 10 weeks.