Do partial lifts grow muscles as well as full lifts?

If you're already fit, doing bicep and tricep exercises through a shorter range of motion—but pushing to your max—can build muscle just as well as doing full reps.

When people lift weights through a full motion vs. just part of the motion, the muscles might look like they grow more in one case—but that could just be because the weight feels heavier at different points, not because the muscle is stretched more. So we can’t be sure if stretching the muscle is what’s causing the growth.

Doing only the bottom part of an exercise (where the muscle is stretched) can build as much muscle in your arms and legs as doing the full movement, as long as you put in the same amount of effort and work.

If you're already experienced with lifting weights, doing exercises where your muscles are stretched out—like lowering a dumbbell all the way down or just partway—gives you about the same muscle growth as going all the way to the extreme stretch. So you don’t need to stretch your muscles to their absolute limit to get big.

When you train one arm, the other arm sometimes gets stronger too—even if you didn’t work it—so if you're trying to see if changing how far you move your arm improves endurance, that mysterious strength boost in the other arm might hide the real effect.