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

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 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.

If two groups of young men lift weights with the same total effort but one rests longer with heavier weights and the other rests briefly with lighter weights, they both get just as strong after 8 weeks—even though you’d think the heavy weights would win.

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.