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.

Even after doing a ton of squats and leg presses, guys can still lift the same heavy weight the next day — their strength doesn’t drop.

Even after doing 21 sets of squats, you can still lift the same heavy weight two days later—your muscles bounce back fast.

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.

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 anywhere from 5 to 20 sets per muscle group each week will make you stronger and build more muscle — and it doesn't matter much which number you pick within that range.