We know adding more sets every two weeks worked in this study, but we don’t know if every week or every month would be better.

If you train a muscle three times a week instead of once, and you end up doing more total work, you’ll get stronger and bigger muscles—better than if you kept the same total work.

If you do the same workout three times a week instead of once, and you end up doing more total weight lifted, you’ll get stronger and build more muscle—because you’re doing more work overall.

If you lift weights the same total amount each week, it doesn’t matter if you do it in one big session or split into three smaller ones—you’ll get just as strong and build just as much muscle.

Even after doing a lot of squats, guys can still lift about the same amount of weight the next day or two—so one tough workout doesn’t make them weaker right away.

If you're already fit and lift weights, doing 5 to 10 sets per muscle group each week will make you stronger—but doing more than that (like 15 to 20 sets) won't make you any stronger, no matter how hard you push.