If you lift weights, your muscles grow bigger — but only up to about 45 sets a week per muscle group; after that, you don’t get much extra growth no matter how much more you train.

If you're a guy who already works out regularly, doing 5, 10, 15, or even 20 sets of exercises per muscle group each week won't make your muscles grow any bigger than the others—after 6 months, they all end up looking about the same.

Doing more sets at the gym than you're used to—like going from 18 to 33 sets a week per muscle group—doesn’t make your muscles grow significantly more, even though you might see a little more growth overall.

If you're already fit and lift weights, doing 5 to 20 sets of exercises for each muscle group every week won't make you grow bigger muscles any more or less than any other number in that range.

Everyone’s body responds differently to workouts—what works wonders for one person might be too much or too little for another, because of differences in genes, energy use, and how fast they recover.

You can't really grow bigger muscles until you've done about 18 weightlifting sessions—your body needs time to adapt before it starts building real muscle.