For older guys doing strength and cardio workouts, their leg muscles only get bigger if they do enough total exercise—how close they push themselves to failure during each set doesn't matter, as long as the overall amount of work is high enough.

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.

When older men get stronger quickly at the start of weight training, it’s often just because they’re learning how to lift better—not because their muscles are growing or getting stronger for real. So, early gains don’t mean they’ll keep getting stronger over time.

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 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 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.