If your shoulders feel tight in Downward Dog, pinch when you reach overhead, or simply won't bind behind your back, the answer often lives in four small muscles most people never think about: the rotator cuff, also known as the SITS muscles.

In this post you'll learn what each rotator cuff muscle does, how they show up in your yoga practice, how to check your shoulder range of motion, and simple drills to build stability and mobility.

What Are the SITS Muscles?

The shoulder is the most mobile joint in the body, and also the least stable. With such a large range of motion, stability is compromised, which makes the muscles that stabilize the joint especially important.

SITS is an acronym for the four rotator cuff muscles:

• Supraspinatus
• Infraspinatus
• Teres minor
• Subscapularis

Together these muscles form a cuff around the shoulder joint whose job is to hold the top of the arm bone (the head of the humerus) securely in the socket, especially while you lift your arm. All four originate on the shoulder blade (scapula) and attach to the humerus.

When the rotator cuff is weak, deconditioned, or lacks range of motion, or when we move with poor form, it becomes vulnerable to pain, strain and tears. That's why it's so important to strengthen these little muscles as often as, if not more often than, the bigger muscles that surround the shoulder.

Rotator Cuff Muscles and Their Functions

All four muscles work together to stabilize the head of the humerus in the glenohumeral (shoulder) joint, but each also has its own job.

Supraspinatus

Located on top of the shoulder blade, the supraspinatus initiates abduction, lifting your arm out to the side, like the arms in Warrior II (Virabhadrasana II). It also helps hold the humerus in place against the pull of gravity.

Infraspinatus

Located just below the supraspinatus, its main role is external rotation of the shoulder, the action you need to keep the shoulders safe in poses like Wheel (Urdhva Dhanurasana) and Downward Dog.

Teres Minor

Found along the outer edge of the shoulder blade toward the armpit, the teres minor works alongside the infraspinatus as an external rotator, assisting in the same poses.

Subscapularis

Hidden on the underside of the shoulder blade, the subscapularis is the main internal rotator of the shoulder. It also helps draw the head of the humerus down and into the socket, protecting the joint from slipping out of place.

Shoulder Range of Motion: The Total Arc of Motion

In athletic training, internal rotation plus external rotation is called the total arc of motion:

Internal rotation + External rotation = Total arc of motion

A commonly used benchmark is a total arc of at least 150 degrees, with a minimum of 50 degrees coming from internal rotation. Having adequate rotation in both directions is a key part of preventing shoulder injuries.

Apply It: External Rotation in Yoga

In Downward Dog (Adho Mukha Svanasana) you'll often hear cues like "spin your biceps toward your ears," "tuck your triceps under," or "spin your hands away from the midline." Each of these is asking you to externally rotate your shoulders.

If you have a hard time feeling your external rotators engage, try this progression:

1. Stand facing a wall.
2. Place your palms flat on the wall with your fingers pointing to the ceiling.
3. Look at your elbows and notice the crease where your arm bends.
4. Rotate your arms so the elbow creases face forward, toward your fingers.
5. Once that feels comfortable, move to a table and add a little weight-bearing.
6. Make your way down to your mat, first on your knees, then fully weight-bearing on your hands.

Throughout, ground down through your index-finger knuckle, keep the weight evenly distributed through your hands, and push the floor away from you.

Apply It: Internal Rotation in Yoga

In Reverse Prayer (Paschima Namaskarasana), including reverse prayer hands in Pyramid Pose (Parsvottanasana), the shoulders are in internal rotation.

If you can't bring your palms together:

• Use a strap behind your back.
• Practice a forward-fold bind: interlace your fingers behind your back, fold forward, and let your arms fall overhead.
• Try the sleeper stretch, a great tool for increasing shoulder internal rotation.

A Simple Self-Test for Shoulder Mobility

To work on internal and external rotation at the same time, try binding your hands behind your back:

• Reach one arm overhead as if combing your hair, then down along your spine (external rotation).
• Bring the other arm behind your low back and reach up (internal rotation).

Notice whether your fingers meet, and how your left and right sides differ. Have a friend snap a photo so you can track your progress as you keep practicing.

Rotator Cuff Injuries: Why They Happen

Shoulder dysfunction is a leading cause of rotator cuff injuries, whether it stems from the shoulder blade, collarbone, or humerus. Usually there's an imbalance somewhere: muscles that are too tight, too weak, or out of alignment. Because so much of daily life and work is repetitive, shoulder injuries tend to develop gradually over time.

The fix starts with learning to properly engage your small stabilizer muscles. Without stability, there are only faulty movement patterns.

Frequently Asked Questions

What does SITS stand for in the rotator cuff?

SITS stands for the four rotator cuff muscles: supraspinatus, infraspinatus, teres minor and subscapularis.

Which rotator cuff muscle is most commonly injured?

The supraspinatus is the most commonly injured rotator cuff muscle, partly because of where its tendon passes over the top of the shoulder.

Can yoga help strengthen the rotator cuff?

Yes. Weight-bearing poses like Plank and Downward Dog, done with active external rotation, help build rotator cuff strength and stability. Pair them with mobility work for internal and external rotation for the best results.

Which muscles externally rotate the shoulder?

The infraspinatus and teres minor are the primary external rotators of the shoulder.

Keep Exploring

Shoulder tension rarely lives in the muscles alone. Learn how the connective tissue that wraps every muscle affects how you move in Why Myofascial Release? Understanding the Web That Holds You Together.

This post is for educational purposes only. If you have shoulder pain or a suspected injury, check in with a qualified healthcare provider before starting a new practice.