If you do the same total amount of weightlifting work, lifting heavy weights a few times or lighter weights more times gives about the same muscle growth in the chest for beginners doing bench press, showing that the total work matters more than how many reps you do.

If you do the same total amount of weightlifting work, lifting heavier weights fewer times or lighter weights more times gives men about the same muscle growth.

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.

When untrained young men lift weights with different heavy loads but equal total work, their chest muscles grow about the same amount—around 10-11% bigger.

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.

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.