If you're a guy who hasn't trained much before, your triceps muscle in the back of your arm grows about the same no matter if you do push-ups, triceps extensions, or a mix of both — the type of exercise doesn't really matter for this part of the muscle.

If you're a young guy who hasn't trained much before, doing exercises like the bench press will make the back part of your triceps grow way more than just doing arm-only exercises like lying triceps extensions.

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.

If you're a guy who's new to lifting and you do both big compound moves and isolated triceps exercises, your triceps will grow more than if you only do one type — not because the exercises add up, but because they hit different parts of the muscle in different ways.

When people who’ve never lifted weights before train their chest and arms with the same total muscle tension time, the back part of their triceps (near the elbow) grows more than the middle or shoulder-end parts.

When guys who work out a little bit lift heavy weights (85% of their max), their triceps muscles grow faster and more reliably than when they lift light weights (30% of their max)—so how heavy you lift might change when your muscles start getting bigger.