If you're already strength-trained, doing full lifts (like fully curling a dumbbell) won't make your muscles grow more than just doing the stretchy part of the movement—so maybe stretching your...

If you're trying to build upper-body muscle and you're already experienced with lifting, it's probably better to focus on the part of the exercise where your muscle is stretched, even if you don't do the full movement. Adding in the part where the muscle is more squished doesn't seem to help you grow more.

Training muscles while they are fully stretched is probably the best way to build muscle size for experienced lifters. Adding exercises that only work the muscle in a shortened position doesn't seem to help you grow more muscle compared to just focusing on the stretched position.

When you stretch your muscles fully during workouts, the ends of the muscles grow more than the middle parts — the stretch makes the muscle ends bulk up more than the center.

When you do strength exercises where your muscles are stretched the most (like lowering a weight fully), you build more muscle than when you only move partway through the motion, no matter which muscle you're working.

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.