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.

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.

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.

Even though guys doing drop sets did only one set instead of three, their muscles grew just as much or more than those who did three sets.

If you're already experienced with weight training, doing 5 to 10 sets per muscle group each week builds just as much muscle and strength as doing 15 to 20 sets—so going over 10 sets won't give you extra gains.

If you're already fit and lift weights, doing 5 to 10 sets per muscle group each week builds just as much muscle and strength as doing 15 to 20 sets—so going overboard doesn't help you get bigger or stronger faster.