The biceps come high up on the list of glamour muscles for most men. It's what you flex when you want to show off your muscles. Go into any gym and you'll see rows of men curling barbells in an attempt to build bulging biceps. Yet the biceps are among the smaller muscles in the body, and they aren't even the biggest muscles in your arms.

Your triceps make up about two thirds of your upper arm muscle mass and, as the name suggests, they are made up of three different muscles or 'heads'. The long head and lateral head combine to form the horseshoe shape at the top of your arm, while the medial head runs beneath the long head down to the elbow. Their job is to straighten your elbow, so they come into play every time you push something away from your body, such as when you do bench presses.