What happens when you lift your arms overhead?
Lifting your arm is a pretty common movement—think shampooing your hair or reaching for a can on a high shelf. It’s also common in yoga practice, from the first movement of a sun salutation to downward facing dog and handstand.
Unfortunately, there are some widespread misconceptions in the yoga world about what happens during this sequence of events. In this post, I’ll dive into the sequence in detail to clear up those misconceptions. This article will mostly focus on what happens when your arms are free to move through space, such at the start of a sun salutation, although much of this information also applies when you’re bearing weight on your hands with your arms overhead, such as in down dog.
Note: I’ve also included a video that explains the same material. You’ll find that video at the end of the post.
Reaching your arm overhead is a complex movement. It requires the coordination of multiple parts of your skeleton working together in a synchronized way. The two bones most directly involved are your shoulder blade, or scapula, and your arm bone, or humerus. For that reason, the sequence is called the scapulohumeral rhythm.
Although in this post I’ll break down the movements of scapulohumeral rhythm one by one, in reality these actions don’t happen successively, but in a simultaneous, synchronized pattern. Hence the term “rhythm.”
Let’s start with the first element. Not surprisingly, your arm has to lift. That’s generically called humeral elevation.
Of course, there are lots of ways to lift your arm overhead. You could bring your arm out to the side and overhead; that’s called shoulder abduction. You could bring your arm forward and overhead, called flexion. You get to the same place, but the pathway is different.
There are many other potential trajectories that your arm could take, but I’ll note one in particular: abducting your arm through the scapular plane, sometimes referred to as scaption
What’s the scapular plane? Let’s start with a little anatomy.The only true joint between the entire shoulder girdle/arm complex and the rest of your skeleton is where your collarbone, or clavicle, joins your sternum, or breastbone. This joint is called the sternoclavicular joint. At the outer end of the collarbone, the clavicle joins to the shoulder blade at the acromioclavicular joint.
The shoulder blade is a triangular-shaped bone, which rests against the surface of the rib cage. On the outer corner of the scapula is the shoulder socket, called the glenoid fossa or glenoid cavity. There is no joint that connects the shoulder blade directly to the spine. Instead, there’s a webbing of muscles that hold it in place and allow it to slide in various directions over the surface of the rib cage.
The ribcage itself not a flat surface. It’s rounded. Because the scapula conforms to its surface, the glenoid fossa doesn’t face directly to the side. Instead, it faces a little forward and out to the side. If you draw a line from the inner edge of the shoulder blade through the shoulder socket, that line defines the scapular plane, which is angled forward about 30 degrees.
Many people will find that lifting through the scapular plane is an easier pathway for the arm to follow than abducting it straight out to the side. One reason is that it doesn’t require as much external rotation.
When your arm abducts, your humerus must also externally rotate. To see why, let’s look at the scapula and humerus in more detail.
Above the glenoid fossa is an overhang of bone called the acromion process. On the front of the scapula is another outcropping of bone, called the coracoid process. The coracoacromial ligament connects the acromion and coracoid processes, forming a vault or roof above the shoulder socket.
At the top of the humerus is a round head that fits into the shoulder socket. On its outer surface is a knob of bone called the greater tubercle.
If you were to abduct your humerus without externally rotating it, the greater tubercle would run into the acromion. That would not only block the movement, but also potentially pinch the soft tissues that run through the subacromial space, including the tendons of one of your rotator cuff muscles, the supraspinatus, and your biceps brachii muscle. This subacromial impingement is a potential source of shoulder pain. However, if you externally rotate your humerus, the greater tubercle moves backward in space, which allows for quite a bit more clearance.
External rotation of your arm during abduction is obligatory, but what about during shoulder flexion? The traditional view has been that shoulder flexion is accompanied by internal rotation of the arm. However, more recent research that suggests that it may actually be accompanied by some external rotation. I think that’s still an open question, but it’s very clear that to abduct your arm, you must externally rotate it.
You can feel this for yourself. Start by bending your elbow and externally rotating your arm, so that the front of your humerus rotates away from the midline of your body and your fingers point out to the side. (The reason I ask you to bend the elbow is to eliminate any contribution from the turning of the forearm bones. That way you know that it’s your upper arm bone that’s rotating.) If you abduct your arm from this position, you’ll find that you have a pretty clear pathway to bring the arm overhead.
However, if you try the same movement starting with your arm internally rotated (so that your forearm lies across the front of your body), you’ll feel that you get jammed up partway. If you externally rotate your arm at that point, you can continue abducting your arm overhead.
You can also feel that shoulder flexion is different. If you start with your arm internally rotated, you’ll see that you can still move it forward and overhead fairly easily.
Scapular upward rotation
The next element of scapulohumeral rhythm is upward rotation of the shoulder blade. This is probably the element in this sequence where there’s the most widespread misunderstanding.
What is scapular upward rotation? As we’ve seen, in its resting position on the back the shoulder blade lies with the glenoid fossa facing to the side (and a little forward). Upwardly rotating your shoulder blade turns the shoulder socket to face upward. At the same time, the lower tip of the scapula protracts, wrapping forward and around the curved surface of the rib cage to wind up on the side of the rib cage, while the inner upper corner, called the superior angle, moves downward.
Why is this necessary? Because even after externally rotating the arm during abduction, the humerus will still run into the acromion before reaching full elevation. To prevent that, the shoulder blade upwardly rotates, moving the acromion out of the way.
These two actions happen more or less simultaneously. During the first 30 degrees of humeral elevation (approximately), your shoulder blade is generally not very involved, but beyond that point, the scapula has to move simultaneously with the humerus to lift your arm fully overhead. That represents 180 degrees of shoulder abduction. About 120 degrees comes from humeral movement. The other 60 degrees is due to the upward rotation of your scapula. In other words, it’s approximately two-to-one arm-to-shoulder blade movement.
This movement of upward rotation is important for a few reasons. One is that moving the acromion out of the way helps prevent impingement of the humerus against the acromion. Also, turning the glenoid fossa upward creates a stable platform to support the head of the humerus.
Maybe even more importantly, upwardly rotating your shoulder blades allows you to preserve an effective length for the muscles that stabilize the head of your humerus in the shoulder socket, as well as the muscles that move and stabilize the shoulder blade on your back.
Muscles work best at close to their resting length. A muscle that’s very long or very short isn’t able to generate force as effectively. Moving the shoulder blade and the arm bone together allows you to preserve a more effective length for those muscles, helping to keep your shoulder stable.
This is a crucial point. There’s a common misconception among yoga teachers that we create stability for the shoulders by fixing the shoulder blades in place—by immobilizing them. That’s what’s behind the frequently heard instruction to keep your shoulder blades pulled down your back when you reach your arms up.
In fact, however, to maintain stability, your shoulder blade has to move. If you keep your shoulder blade pulled down, you’re not going to be able to get full reach overhead because you’re blocking the movement. Plus, you’re running the risk of creating some potential problems for the shoulder over the long haul.
However, there is a seed of truth in that instruction. As the glenoid fossa lifts, the superior angle can release down away from your neck. This might be a helpful action for you to visualize when lifting your arms, because it can create a sense that your shoulder blades counterweight your arms, helping them feel lighter. But that’s very different from pulling your entire shoulder blade down your back, which will only block the movement.
Scapular posterior tilting
The next element of scapulohumeral rhythm is scapular posterior tilting.
In its resting position, the top of your shoulder blade is tilted forward a little. That’s the natural positioning due to the shape of the rib cage, which is a narrower at the top than in the middle.
When you lift your arm, your shoulder blade posteriorly tilts. In other words, the top of your scapula tips backward. This helps further move the acromion out of the way of the head of the humerus.
You can feel this for yourself. If you exaggerate the anterior, or forward, tilting of your shoulder blades and try to lift your arms, you’ll feel you get stuck. But if you tilt the tops of your scapulae back, you’ll find you have more clearance.
Posterior tilting is a smaller movement than upward rotation—only about 20 degrees or so. Bear in mind, though, that there is a lot of individual variation between people, so take all these numbers with a grain of salt. You may have more or less posterior tilting, or upward rotation, than someone else. That doesn’t mean there’s a problem. It just means people are different.
Scapular external rotation
The next element of scapular humeral rhythm is scapular external rotation.
Recall that in the resting position your shoulder socket doesn’t face directly to the side, but a little forward, which defines the scapular plane. In that resting position, you could say that the shoulder blades are internally rotated (although that’s stretching the terminology a bit).
To find full elevation of your arm, the outer part of your shoulder blade has to rotate back a little. That’s scapular external rotation. It’s a pretty small amount of movement—about 10 degrees or so. (And, since the shoulder blades start about 30 degrees “internally rotated,” even with that external rotation, the final position of the scapulae is still somewhat internally rotated.)
This external rotation is a different movement than retraction of the scapulae, i.e. pulling them closer to the spine. In fact, when you elevate your arms, the lower part of your scapula has to protract, or move away from your spine. That’s part of the movement of upward rotation. The lower tip, or inferior angle, wraps around toward the side of the rib cage, effectively protracting the shoulder blade.
Clavicular elevation and posterior rotation
Although I’m focusing here on the movements of the scapula and humerus, they don’t move in isolation. The clavicle is attached to the scapula, so when your scapula moves, your collarbone moves too.
As the scapula upwardly rotates, the outer end of the collarbone lifts along with it. Due to the pull on one of the ligaments that joins it to the scapula, the clavicle also posteriorly rotates along its long axis. Plus, the outer end of the collarbone moves backward, or retracts, as the scapula posteriorly tilts.
Although not technically part of scapulohumeral rhythm, some movement of the thoracic spine, or the spine of the ribcage, also accompanies reaching your arms overhead.
The natural shape of the thoracic spine is rounded toward the back. But when you bring your arms overhead, the thoracic spine extends, flattening that curve, which allows the sternum to lift.
This is different from tilting the entire rib cage backward, i.e. hinging at the junction between the lumbar and thoracic spine. I sometimes see students doing this as way to compensate for lack of full arm elevation, but this habit can introduce an energy leak into the kinetic chain from the ground to the shoulders. Instead, look for an internal lift within the rib cage itself that supports the arms.
That’s if you’re lifting both arms together. If you’re lifting one arm, some thoracic extension is helpful as well, but the thoracic spine also laterally flexes. In other words, it side bends a little. If you’re reaching your right arm up, the rib cage on your right side lifts and lengthens, and of course, the left side shortens a little. This helps get more support under the lifting arm.
So what does this mean in practice?
What’s the takeaway from all of this information? How can you apply it into your own practice?
First, keep in mind that your brain already knows this sequence. You’ve been bringing your arms overhead for most of your life. Even if you never heard of scapulohumeral rhythm before, your brain knows how to coordinate the actions of your shoulder blade and arm in a synchronized way to accomplish that movement. So, the primary piece of advice I have is to get out of the way. Stop impeding the movement.
Don’t take this information and try to micromanage the sequence. That’s going to be counterproductive because the ingrained patterns of neuromuscular activation in your brain are much more effective at guiding the movement than your conscious mind. Instead, let your brain do what it already knows how to do.
This is especially important because of the tremendous amount of individual variability in these movements. Some people externally rotate their arm a little more, some people a little less; some people upwardly rotate the scapula little more, some people a little less. That’s all normal variability. Your brain has to figure out how best to coordinate these movements for your skeleton. Trying to micromanage the movement will likely only interfere with that coordination.
An example of this is the instruction I referred to earlier—pulling the shoulder blades down as you lift the arms overhead. As you’ve seen, that will block the movement of the arms and make the action more difficult. Rather than trying to control the movement of the scapulae consciously, allow them to move naturally.
At the same time, I think understanding the sequence can be helpful if you view it as a set of guideposts for your awareness. If you run into difficulty someplace in the movement, knowing the steps can help you focus your attention. And through attending to the feeling of the movement, you may find a way to adjust some part of the sequence to find more ease and comfort.
Experiment with different pathways for taking your arms overhead. Remember, moving in the scapular plane rather than directly to the side may be easier for you. Or you may find that bending your elbows and bringing your arms up through the center line is easier. Bending your elbow reduces the lever arm, so that there’s less effort required from your shoulder musculature. Play around. Find the trajectory that works for you.
Also, pay attention to what’s happening in your rib cage. Can you find a feeling of support underneath your arms when they’re reaching overhead? Inhaling as you reach up may help you find more thoracic extension. If you can find some support from your breath, that’s going to help to create more support and stability underneath your arms.
And finally, remember that support for your shoulders ultimately comes from the ground up. Your shoulders don’t work in isolation from the rest of you. Pay attention to the entire kinetic chain from your feet to your hips to your spine to your ribcage and shoulder girdle, and look to create a clear pathway through your skeleton to connect to the support of the earth below you.
Neumann D. Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation. Mosby, 2012.
Oatis C. Kinesiology: The Mechanics and Pathomechanics of Human Movement. Wolters Kluwer, 2017.