Even the smaller parts of your triceps grow more when you do the exercise with your arm overhead instead of at your side.

When you do triceps exercises with your arm stretched overhead instead of at your side, your triceps muscle grows more—even if you’re lifting lighter weights.

Overall, your whole triceps muscle grows more when you do the exercise with your arm overhead—even if you’re not lifting as heavy.

If you're a young guy who hasn't trained much before, doing exercises that only move your elbow (like lying triceps presses) makes your triceps muscle grow way more than doing exercises like bench presses that use multiple joints at once.

In untrained young women, training the biceps through the fully bent position of the elbow for eight weeks does not lead to more muscle growth than training through the partially bent position, when measured by muscle size at specific points along the upper arm.

In untrained young women, performing bicep exercises using only the first half of the movement range for eight weeks leads to more muscle growth in the lower part of the biceps and greater strength gains than using only the second half of the range.