If you're lifting heavy weights and stop just before your muscles give out, you'll still gain about as much muscle as if you pushed to the very last rep you can possibly do.

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.

When people lift light weights until they can't anymore, their thigh muscles grow much more than if they just lift lightly without pushing to the limit, showing that working really hard is key for muscle growth even with light weights.

If you lift weights until you can’t do another rep—whether you use heavy weights or light ones—you’ll end up with about the same muscle growth after nine weeks, as long as you’re putting in the same effort and number of reps.

Lifting heavy weights and lifting lighter weights both build muscle about the same amount in healthy adults, as long as you do enough reps until you can't lift anymore.

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.