For older people, lifting weights once or four times a week might not make much difference in how much stronger they get—but it could make a big difference in how much their muscles grow.

For older people lifting weights, doing just one set of exercises builds just as much strength as doing four sets—so more sets don’t necessarily mean stronger muscles.

If you're an older adult who gets stronger with just a little bit of weight training, doing more sets won't make you any stronger than doing just one set.

If older people who didn’t get stronger from doing just one set of weight exercises start doing four sets instead, they’ll likely grow bigger muscles in their thighs after 10 weeks of working out twice a week.

If you're an older adult who's already getting stronger from light weight training, doing even more weight training might help you build even more muscle—but not as much as it helps people who didn't respond to light training at all.

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.