If you're over 60 and lifting weights, doing it more than twice a week probably won't make you any stronger or give you bigger muscles than doing it just twice a week.

For people over 60, adding one extra day of weight training each week might help them get a little stronger, but it won’t make their muscles noticeably bigger.

Lifting weights three times a week instead of two makes your muscles grow bigger, no matter what type of muscle fibers you have — but it doesn’t make you stronger in one-rep max lifts.

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 older men in their early 70s lift heavy weights three times a week for four months, they’ll get noticeably stronger and their big muscle fibers will grow bigger.

If you're already strong and lift weights, training each muscle group either once or five times a week for eight weeks will give you about the same strength gains on the bench press, squat, and row.