If you train one leg of an older adult with light weights and leave the other leg alone, scientists can tell whether that person’s muscles grow in response — and use that to figure out who benefits from this kind of training and who doesn’t.

If older adults do not gain muscle from regular weight training, doing more sets and reps might help them finally start building muscle.

Some older people’s muscles grow when they lift weights, and others don’t — this claim says that changing how many times you lift can tell the difference between those who grow and those who don’t, based on how much their thigh muscle size changes after just one set.

If older people who didn’t get stronger from doing just one set of weight exercises start doing four sets instead, their thigh muscles will grow bigger — and this was measured with a detailed scan.

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 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.