little known muscle series – infraspinatus & teres minor

Time for another installment of … the little known muscle series. Today I’ll highlight 2 muscles that work in tandem. They are infraspinatus and teres minor.They are part of the shoulder’s rotator cuff.

Muscle mapquest: These muscles are found on the back of the shoulder blade. They lie at an angle more or less pointing up towards the top of the arm bone.

What do they do? As part of the rotator cuff, they work to stabilize the arm in the shoulder joint. Our shoulder joint is designed to allow for maximum range of motion. The trade-off is decreased stability. In addition to ligaments, there are 4 main muscles serving to stabilize the joint. Infraspinatus and teres minor partner with supraspinatus and subscapularis to accomplish this stability. Each of these muscles has its own action. Infraspinatus and teres minor laterally rotate the arm bone (humerus) in the shoulder joint. They also adduct, extend and horizontally abduct the arm. **Anatomy nerds see below for more detail on these fascinating actions.

The other main function of infraspinatus and teres minor is to act as brakes. Other muscles that move the arm are much bigger and stronger, like the pectoralis major, a big chest muscle. Pectoralis major is an antagonist to our subject muscles, as well as latissimus dorsi and teres major (in rotation). An antagonist in anatomy terms is a muscle that does the opposite action. To understand this important braking action, imagine a baseball pitcher throwing a 90-mile-an-hour fastball. It’s a wonder his arm doesn’t just fly out of the socket right behind the ball. Well, this demonstrates the action of the infraspinatus and teres minor. They stomp on the brakes so as to prevent dislocation, tears and sprains. At least they try to!

Why they are sore: Because these muscles are smaller in relation to their bigger antagonists and because they are typically weaker and less developed than the big guns, it’s not uncommon for them to be sore upon palpation (touching them) or massage. They can also be overwhelmed by sudden loads or overexertion. They are sore on most people I see for massage. And most people are surprised. “What’s that?” they ask. I don’t massage any MLB pitchers, so why are they sore on the average person? They are sore on most people because everything we do is in front of us: driving, working at the computer, doing the dishes, holding kids, etc. Our forward activities cause us to curl inward in our posture and this puts these small muscles in a constant stretch position. This makes them cranky. Weak, underdeveloped muscles tend to be sore because they are overpowered by their antagonists. Here’s what we can do to make them happier –

Loosen them: Massage is great for loosening up these muscles and for simply drawing our attention to them. If we don’t know a muscle is sore, we probably won’t pay any attention to it. Between professional massages, you can massage these muscles yourself at home. All you need is a tennis ball and a wall. Stand with your back against a wall. Place the tennis ball between you and the wall with the ball positioned where your shoulder blade is. Push your weight into the ball and roll it around until you find a spot that feels sore. This is a great way to massage your back in general. To find this infraspinatus and teres minor spot, I find it helpful to raise my arm to the side so it’s parallel with the floor. I scoot the ball over so that it’s at the edge of the shoulder blade along the border. When I find a “hurt so good” spot, I move my body so the ball massages the spot in a circular motion. Limit your tennis ball massage time to a short amount, like a minute or two. You can repeat it throughout the day, but keep it short each time otherwise you’ll make yourself really sore. Trust me – respect the tennis ball!

Strengthen them: A healthy shoulder has equally strong and developed rotator cuff muscles that stabilize the arm in the joint. If you participate in a sport or hobby that is shoulder- or arm-intensive, it would be smart to make sure you develop strength in all the rotator cuff muscles. A good trainer, physical therapist or even massage therapist can help you figure out what exercises you can do to strengthen what’s weak. You can also spend some time learning about medial and lateral rotation, abduction and adduction, flexion and extension, etc. and put together a regimen that addresses each action. Most men I know are interested in developing a super-burly looking chest by developing pectoralis major, and neglect these important stabilizer muscles. Don’t be like most men! Be smarter.

Comments? Questions? I hope this is helpful. Now go enjoy this amazing range of motion you’ve been given!

** Anatomy nerds: To understand rotation of the arm stand with arms hanging at your sides. When you laterally rotate your arms you rotate them so that your thumbs turn away from your body. The opposite would be medial rotation (rotate them so that the backs of your hands turn in toward your legs). Adduction is seen when you start with arms straight out to the sides at 90 degrees. Bring the arms down to the body. Extention is the action of moving the arms behind your body from a starting position of arms hanging at your sides. To see horizontal abduction, start with straight arms out to your sides at 90 degrees. Move the arms back behind the body in the same plane. Get the picture?


5 thoughts on “little known muscle series – infraspinatus & teres minor

  1. Dean says:

    Thank you….. I’m a hairdresser and do weight fitness in my spare time, and this has been a sore point on me for a very long time, more recently though. It’s a relief to know what the cause is. Does this go away at any point, or will this always be there…???

    • Thanks for reading the blog and commenting. Each comment is an encouragement. “does this go away?” is a great question. These muscles respond well to massage. You can also give them a little massage yourself by leaning into them with a tennis ball between you and the wall. It gives a good squeeze to the muscles. You can also do some targeted weight training to strengthen them. They are less cranky when they have the appropriate amount of strength. Best of luck, Susan

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