You might be surprised how much you're already hitting this valuable muscle group. Here's how to avoid going overboard.

One of the most important arm muscles is the triceps brachii (the triceps, for short). You use your triceps to extend your arm. It opposes the biceps muscle, which is used to flex the arm. You also ...

How to do it: Stand holding dumbbells by your sides, palms facing each other. Bend one elbow to lift the dumbbell to your ...