If you lift weights until you can’t do another rep, your muscles will grow about the same no matter how heavy the weights are—but you’ll get stronger faster if you lift heavier weights.

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.

Lifting light weights until you can't do another rep builds muscle just as well as lifting light weights until your speed slows down a lot, as long as you do the same total amount of work.

When resistance training is performed to volitional muscular failure, hypertrophic outcomes are equivalent across a wide range of loads (from low to high) and repetition ranges.

If you lift weights until you're almost too tired to do another rep, you'll likely build bigger muscles—but your strength gains won't be any better than if you stopped earlier, as long as you're doing the same total amount of work and lifting the same weight.