When untrained young men lift weights until they can't anymore, both heavy and light weights make their muscles grow about the same amount (6% bigger) if they do the same total work. This goes against the common belief that heavier weights are always better for muscle growth.

When untrained young men lift weights until they can't anymore three times a week for six weeks, and they do the same total amount of work, their muscles grow about the same amount whether they lift heavy or 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.

If you lift light or heavy weights but do the same total amount of work, your muscles grow about the same amount—whether you're using light dumbbells or heavy barbells.

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.

If you lift light or heavy weights but do the same total amount of work, your muscles grow about the same amount—so lifting light weights can be just as good for building muscle as lifting heavy ones.