Understanding Arm Muscle Basics

Your biceps muscle spans the front of your upper arm. Hang out in any gym and you’ll see people flexing these muscles in the mirror, usually when they think that nobody’s watching. The main job of your biceps (nicknamed your is or your guns) is to bend your arm; in gymspeak, this motion is called curling or flexing.
Your triceps, located directly opposite your biceps, spans the rear of your upper arm. The biceps and triceps, like many muscle groups, work together in pairs. When you squeeze your biceps, your triceps relaxes and your arm bends, and when you squeeze your triceps, your biceps relaxes and your arm straightens. Maintaining a good balance of strength in the relationship between the two muscles is important so that one muscle doesn’t dominate the other. That’s why you need to train both.
Another group of arm muscles allows your wrists to move in a variety of ways. To spare you some jargon, we’re going to refer to these as your wrist muscles. These muscles let you bend your wrist up, arch it down, twirl it in a circle, tilt it left and right, and turn your palm up or down. One of the most important jobs of the wrist muscles is to keep the wrist stable and the wrist joint flat or neutral. If your wrists are weak, the wrist muscles can bend at inopportune times (like when you’re holding a 100-pound barbell over your chest). Weak wrists also mean that you can’t get a grip — on a baseball bat, a stubborn weed, or a can of mushroom soup — and leave you prone to conditions like carpal tunnel syndrome, an inflammation of your wrist nerves.