When young male athletes lift weights until they can't anymore, it doesn't matter much whether they use heavy weights or lighter ones—both ways build about the same amount of muscle after 8 weeks.

When young male athletes push themselves as hard as they can in weight training, whether using heavy or light weights, their muscles grow about the same amount after 8 weeks.

Whether you lift heavy weights with fewer reps or light weights with more reps—as long as you push until you can’t do another rep—your muscles grow about the same amount.

Whether you lift light weights with lots of reps or heavy weights with few reps—so long as you push until you can’t do another rep—you’ll build muscle about the same amount.

If you lift weights until you can’t do another rep, it doesn’t matter if you’re using light, medium, or heavy weights—you’ll still grow your muscles about the same, as long as you push yourself hard and do enough total work.

Whether you lift heavy weights for fewer reps or light weights for more reps—as long as you push until you can’t do another rep—your muscles grow about the same amount.