Which Muscle Is That? Part 2

In my last post I discussed the muscles of the lower extremities.  Now is time to go into the muscles of the upper extremities which are your arms.  As with the previous article, I will stick to the basics of what you need to know.  If you have any other specific questions, you can always ask me.  Oh ya, isn’t this a cool tattoo?

Muscles Of The Shoulder

Deltoid:  The deltoid is actually separated into three sections.  The anterior deltoid is on the front of your shoulder and helps to move your arm in a forward direction.  The middle deltoid runs over the outside of your shoulder and helps to move your arm out to the side.  The posterior deltoid is on the back of your shoulder and helps to move your arm straight back behind you.  This is mainly what you’re trying to train when you do forward and lateral raises.

Rotator Cuff:  The rotator cuff is actually made up of four different muscles that all originate on your scapula, or shoulder blade, somewhere and attach onto the upper part of the humerus which is your upper arm bone.  These are all very small muscles and they seem to be easily injured.  Here’s the list.

  • Supraspinatus:  This muscle acts to help lift your arm out to the side.
  • Infraspinatus:  The infraspinatus helps to laterally or externally rotate your shoulder.  This     means to rotate it away from your body.
  • Teres Minor:  This muscle also aids in external rotation.
  • Subscapularis:  This muscle helps to medially or internally rotate your shoulder.  This means to rotate your arm in towards yourself.

These four muscles do help to move your shoulder in various directions, but together their most important function is to keep your humeral head centered in your glenoid during activities.  This means to keep the ball in the socket.  Therefore, unless you’re at rest, these muscles are almost always being used.

Muscles Of The Upper Arm

Biceps Brachii:  The biceps sit on the front of your upper arm and go from your shoulder to your elbow.  This muscle has two heads, hence the name.  The biceps can work to bend your elbow and also help to move your shoulder in a forward direction.

Triceps Brachii:  This is the muscle that runs along the back of your arm from your shoulder to your elbow.  It has three heads, the long head, medial head, and lateral head.  The long head works to straighten your elbow and can also help to extend your shoulder causing your arm to reach behind you.  The other two head only help to straighten the elbow.

Brachialis:  This muscle is also on the front of the upper arm.  It runs from the humerus to the elbow and is responsible for helping to bend your elbow.

Brachioradialis:  This muscle also runs from the humerus to the elbow and helps to bend your elbow as well, particularly when your hand is in the thumbs up position.  In school we used to call this one the drinking muscle.

Muscles Of The Forearm

Extensor Carpi Radialis Longus and Brevis:  These muscles run from your elbow to your hand and are mostly responsible for bending your wrist backwards.

Extensor Carpi Ulnaris:  This muscle has a similar function to the extensor carpi radialis muscles.

Extensor Digitorum:  This muscle originates on the outside of your elbow, runs down the back of your forearm and goes into your hand.  It is responsible for extending your wrist and fingers.  This is the primary muscle and tendon involved in tennis elbow.

Flexor Carpi Radialis and Flexor Carpi Ulnaris:  These originate on the outside of your elbow and run along the front of your forearm into your hand.  Their main function is to flex or bend your wrist forward.

Flexor Digitorum Superficialis:  This muscle also runs along the front of your forearm down into your fingers and helps to flex or bend your fingers.

So these are the major muscles of the upper extremities.  I’ve left out some of the small muscles in the arm and also most of the muscles that are located in the hand because there are a lot of them and they’re not necessarily important to this article.

I hope you find the information here useful the next time you’re in the gym trying to figure out how to work certain muscle groups or when you’re taking a class and you’re wondering why the instructor is having you do certain exercises.  I’ll be back in the future with articles on the back, chest, and abs.  Stay tuned.

photo credit: Foxtongue via photopin cc

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