Even if you work out your arms regularly, you might be missing this one muscle: the triceps. That's why a trainer says this is her top arm strength exercise.

If your arm day training session is stuck in the same old slog of biceps curls to triceps pressdowns—then wash, rinse, repeat—it's far past time that you introduce some variety into your workout. Take ...

But when the muscle that runs from your shoulder down to your elbow pops, it signals serious strength-likely from mastering the triceps kickback. How to: Stand with your knees bent and lean forward ...