Yoga teachers can be a bit like the Wizard of Oz—they make demands from behind an all-knowing curtain but fail to give students an explanation for their cues. This series aims to pull back the curtain and expose the method behind what might sometimes seem like madness.
Chances are good that you’ve heard a teacher cue you to “roll your upper arm bones” in poses like Adho Mukha Svanasana (Downward Facing Dog Pose), Adho Mukha Vrksasana (Handstand), and Urdhva Dhanurasana (Wheel Pose). The cue is meant to help you open your chest and relax your neck muscles. But the shoulder joint is more complicated than it might seem and understanding the biomechanics of the joint and how it relates to asana is essential to a safe and beneficial practice.
Anatomy of the cue
When your teacher says to “roll the upper arm bones out” or “roll the head of the humerus back,” they’re asking you to externally rotate the glenohumeral joint, a ball-and-socket joint between the humerus (upper arm bone) and scapula (shoulder blade).
This joint is incredibly mobile, but not very stable. The head of the humerus is larger than the socket it sits in, and is only held in place by ligaments and muscles. One of those muscles, the supraspinatus, is part of the rotator cuff; it runs through the joint (as does the long head of the biceps muscle) and helps to stabilize the head of the humerus. One of the most common shoulder joint injuries I see among yoga practitioners is supraspinatus tendonitis, or an inflammation of this tendon, which leads to pain and a decreased range of motion.
What your teacher wants you to do
When a teacher says to roll the upper arm bones back, it’s because they want to make sure the head of the humerus sits in the proper position within the joint, so that there is optimal space between the bony surfaces allowing for full range of motion without pinching any of the structures that are within it.
Ideally, you should avoid practicing postures with the upper arm bones rolled inward, so that the chest is broad and there is plenty of space within the shoulder joint for the tendons to move freely and for the cartilage to remain intact. Your teacher wants you to keep the shoulders “in joint” so that forces are transmitted evenly throughout the arm bones to the torso without compromising the vulnerable structures within the shoulder.
Your teacher also wants you to be able to access the proper muscles required to stabilize the shoulder—such as the rotator cuff, the lower trapezius, and the serratus anterior—instead of using muscles that can cause tension, like the upper trapezius and scalenes in your neck.
Why this cue can be dangerous
“Roll your upper arm bones back” may work for individuals who are tight in the anterior shoulder and chest area. But for most yoga practitioners—who tend toward being hypermobile—this instruction can actually be a dangerous one, especially when your arms are raised overhead in full flexion. Here’s why: A capsule filled with synovial fluid surrounds and lubricates the glenohumeral joint and acts as a shock absorber. If you have poor posture—when your chest collapses, your upper back rounds, and your shoulders roll inward—the head of the humerus sits somewhat ‘out of joint,’ causing the posterior aspect of the shoulder capsule to tighten up. This results in compromised shoulder mobility, which can compress the supraspinatus and long head of the biceps tendon when the arms are raised into full flexion. If this happens, you’ll likely feel pain when you move your arms directly overhead—or you may not be able to complete that action at all.
Emphasizing this cue in poses where your weight is born by your arms, such as Adho Mukha Svanasana (Downward-Facing Dog) or Adho Mukha Vrksasana (Handstand) is even more concerning. When your arms bear your weight in these poses, the head of the humerus is drawn closer to the acromion process (the top outer edge of your scapula). When you “roll the head of the shoulder back” while bearing weight on your arms, it can lead to a “shearing force” in which the head of the humerus pushes in one direction while the scapula moves in the opposite direction. Shearing forces are what cause arthritis of degeneration of joint surfaces. Adding a rotational force combined with compression can pinch and injure the fragile tendons, cartilage, and other structures in the shoulder capsule.
What your teacher could say instead
Instead of focusing on moving the humerus within the shoulder joint, I recommend an instruction that focuses on movement of the shoulder blades and target the scapula.
Instead of “roll the upper arms back” your teacher could say “spread your shoulder blades wide on your back” or to ‘move the shoulder blades away from the spine.” Doing this activates the serratus anterior, a fan-shaped muscle that spans the upper eight or nine ribs and helps you move your scapula forward and up into the correct position. This maintains the integrity of the shoulder joint and avoids compressing the tendons and tissues within the joint itself.
In addition, when you activate the serratus anterior, the upper trapezius automatically relaxes—this releases tension in the muscles in your neck and upper back and helps you maintain the proper curve in your cervical spine.
Try it yourself
To become familiar with the action of spreading your shoulder blades, try this exercise: Stand facing a wall and place your forearms against it with your hands clasped as if you are preparing for headstand position. Keep your elbows in line with your shoulders and press the inner edges of the forearms and hands firmly against the wall.
As you inhale, allow the shoulder blades to come together in retraction as you move the thoracic spine towards your chest. As you exhale, press your forearms and the outer edges of your hands and wrists into the wall. Feel the shoulder blades move apart and “fill up” your upper back, so that it is not collapsed. Repeat this 10 times, moving the shoulder blades together as you inhale and spreading them apart as you exhale. Now you are strengthening your serratus anterior muscles!
After repeating this set two or three times, stand in Tadasana (Mountain Pose) and notice the sensations in your body. You may feel that your neck or upper trapezius is more relaxed, or that your chest is more open. You may even notice that your shoulders are sitting in their proper position alongside the body.
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About our contributor
Rachel Krentzman is a physical therapist, certified yoga therapist and author of two books: Yoga for a Happy Back: A Teacher’s Guide to Spinal Health through Yoga Therapy and Scoliosis, Yoga Therapy and the Art of Letting Go. She is the founder of Happy Back Yoga Academy, an online continuing education training for yoga teachers and practitioners who want to learn how to use yoga for therapeutic purposes. She is passionate about integrating yoga into the healthcare system.