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.

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.

If you lift light weights for more reps or heavy weights for fewer reps—but do the same total amount of work—you’ll grow your muscles just as much either way.

Lifting heavier weights might make your fast-twitch muscle fibers grow more than lighter weights, but the results aren't totally certain.

The total amount of work done (weight × reps × sets) seems to matter for muscle growth — more work generally leads to more muscle, even if the weights are light.

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.