To find teres major, reach across and grab the flesh that forms the back of your armpit, with your thumb in your armpit and your fingertips on the outside edge of your shoulder blade. If you slide your thumb back and forth, you can feel the dense and slippery tendon of your latissimus dorsi (or lat) muscle. You can follow it as it curves up around into the humerus (upper arm bone). The lat comes from your lower back, connecting into the fascia of your thoracic and lumbar spine, hip, and even your outer ribs, and eventually winding into a flat, wide tendon that attaches to your upper arm.
Under your fingertips is your lat’s good friend, and our focus: teres major (meaning “big round” in Latin)—a much shorter, square muscle that runs from the bottom corner of your shoulder blade and joins into the humerus right beside, and parallel to, the lat.
What you are holding when you hold the back of your armpit is the control panel for the proper positioning of your shoulder in inversions. The lats and teres major form part of the big X across your back that I call the Back Functional Line. This myofascial (muscular plus fascial) line connects from the end of the lat on your arm, all the way across your back, to your opposite hip and leg.
While your lats are broad surface muscles that usually lengthen and strengthen pretty quickly with initial yoga practice, teres major is, by contrast, not very well known or understood in the context of movement. The myofascial pathway through teres major requires more attention to get balanced. I call this pathway the Deep Back Arm Line—another myofascial line of connection that starts with the little- finger side of your hand and ends at your thoracic spine. The idea is to get even muscular and fascial tone through the whole Deep Back Arm Line. You can do it; it just requires attention.
Teres major is key to supporting your weight when you move upside down. If teres major is too short, you’ll be setting yourself up for a shoulder injury as you load your shoulder with more weight in increasingly difficult or long inversions.
The Deep Back Arm Lines (yellow) run from the tips of your little fingers up your arms, eventually reaching your shoulder blades and the center of your back to your neck. The Back Functional Lines (blue) connect to the ends of your lats, cross your lower back, and end at opposite hips and legs.
Feel your deep back arm lines and back functional lines
Become aware of these lines when you go upside down. Take any inversion—from simply being on all fours in Down Dog to Headstand or Handstand—that’s easy and non-injurious for you.
Ground through the heels of your hands, or your little fingers and your outer arm bones (ulnas) if you’re in Headstand or Pincha Mayurasana (Forearm Balance), and feel up through the myofascial line outside your lower arms to the olecranon (the point of the elbow). These are your Deep Back Arm Lines. From here, the myofascial connection runs into and up the triceps, which may be insufficiently toned in many beginning yoga students, and unable to sustain balance with the rest of this pathway. (Do your Plank Poses to get those triceps posturally strong!)
From the triceps of each arm, the Deep Back Arm Line runs into the rotator cuff surrounding the scapula. The lats reach far away to the back of the torso, but try to put your mind into the shorter teres major, which links the triceps with the lower tip of the scapula. Can you feel your shoulder blade at the end of your triceps? Can you place your scapula on top of your humeral head (the ball in the ball-and-socket joint), and at the same time pull it down onto your ribs?
The rotator cuff, which I call the “scapula sandwich,” is a thin slice of scapula between the surrounding cuff of muscles. It gets hooked to the spine by the rhomboids and the levator scapulae. In the inversion, can you feel this hook into the upper back and cervical spine?
The rotator-cuff muscles—supraspinatus, infraspinatus, teres minor, and subscapularis—surround the ball of the shoulder. Lots of people get into trouble with the rotator cuff (think baseball pitchers and tennis players), but for yoga folks, the trouble spot is often teres major.
So expand your awareness to the whole Deep Back Arm Line. Where does it feel weak? Can you feel it connecting all the way up? Often the triceps are the weak part, and the teres major is the overly short part, creating a short circuit in the whole “using your arm as a leg” thing.
You can sharpen your awareness of teres major by practicing a short vinyasa. In Down Dog: Ground through the outer heel of your hand and little finger, tone your triceps, and feel the connection build up through your Deep Back Arm Lines. Track the lines specifically through the back of your armpits, through teres major, and into the Back Functional Line.
Now move slowly through cycles of Down Dog and Plank Pose. Feel how the shifting angle of your shoulders, and different weight-bearing in your arms, travels through the Deep Back Arm Lines to your mid spine in Plank and extends across your lower back and Back Functional Line as you move into Down Dog. In Plank, these lines act independently, but in inversions, the lines connect through the teres major. The key to sustaining happy inversions lies in allowing teres major to lengthen as you move back into Down Dog. If it can’t lengthen, the foundation of support through your shoulder will be lost. As you extend your elbows, keep your humerus bones and triceps connected to your lower arms, but make sure your scapulae stay connected to your back and ribs. Feel the stretch? That’s your teres major creaking open at last.
Shift onto one arm (you can drop a knee or two to the ground) and grab the back of an armpit to feel your teres major and enhance your awareness of where you need to stretch. Most people need to let this muscle go in order to strengthen the triceps and rotator cuffs. If you can find teres major and let it go, you’ll become more aware of your arm connecting to the outside of your hand, and the tip of your shoulder blade connecting to your ribs. If teres major is too short, it will hook the whole shoulder blade into your arm, setting you up for a shoulder injury as you load it with more weight in increasingly difficult inversions.
Join Tom Myers for a seven-week online introduction to anatomy for yoga students and teachers. You’ll learn how to think of movement in holistic, relational, and practical ways, and how to identify common postural patterns—plus strategies for cueing to awaken parts of the body that may need work.
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