Even though the guys doing the most workouts looked like they might have grown a little more, the difference wasn’t big enough to say for sure that more sets = more muscle.

If you lift weights the same total amount each week, it doesn’t really matter whether you do it in one big session or spread it out over several days—your muscles will grow about the same either way.

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'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.

Doing more sets of weightlifting each week helps you build more muscle, but after a certain point, adding even more sets gives you less extra benefit.

Doing more weightlifting each week helps you build more muscle—but only up to a point. After a certain number of sets, doing even more doesn’t help much more.