I was working with a young dancer this week whom I’m still getting to know. As I was teaching her one of the bread and butter strength training movements—the bench supported dumbbell row—I noticed something fascinating that wasn’t obvious in other exercises like seated rows. She had poor scapulohumeral rhythm on her right side only.
Scapulohumeral rhythm sounds intense, but if you break down the anatomy then you’ll begin to understand both why it’s important and how it could lead to problems for female dancers even when they’re not responsible for lifting overhead (though that is changing in the dance world).
The scapulo part of the phrase refers to the scapula, or shoulder blade. Humeral refers to the humerus, which is the big bone in our upper arm. Scapulohumeral rhythm refers to the kinematic (or movement) relationship between the scapula and the humerus. Scapulohumeral rhythm is particularly important when we lift our arms overhead. In the case of the young dancer whom I was training, her right humerus moved independently of her scapula, which eventually will cause her shoulder pain and could potentially lead to other issues further down the kinematic chain (low back, hips, etc.).
I should pause and give a nod to Eric Cressey, whose work around shoulders in strength and conditioning has been instrumental to our understanding of these issues. Through him, we found Shirley A. Sahrmann’s seminal text “Diagnosis and Treatment of Movement Impairment Syndromes.” As a strength coach, it’s not my job to either diagnose or treat—that’s a physical therapist’s lane of the road—but I can’t do my preventative and performance-enhancing job without a solid understanding of how aberrant movement can affect athletes.
Cressey and Sahrmann emphasize the critical role of the serratus anterior muscle in promoting healthy shoulder movement. Here’s Sahrmann from her aforementioned text:
The serratus anterior muscle abducts and upwardly (laterally) rotates the scapula and holds the scapula flat against the rib cage. The upward rotation is produced by the force couple action of the serratus anterior muscle with the trapezius muscle. The serratus anterior muscle is the primary abductor of the scapula. Complete active range of shoulder flexion/elevation motion is not possible when the serratus anterior muscle is paralyzed or becomes severely weak. In addition, deficient control by the serratus anterior muscle, causing impairments in timing and rage of scapular motion, can cause stress at the glenohumeral joint. (emphasis added)
Sahrmann goes on to write that she “has found that impaired control of the scapula by the serratus anterior muscle is common.” My young dancer client for right now is asymptomatic, but my job as a strength and conditioning coach is to make sure she learns how to use her serratus anterior so that we can avoid any problems before they start. Otherwise, she’ll be the dancer who complains of shoulder issues, or worse, hurts herself lifting a heavy bag above her head when she’s traveling to perform or audition.
One can sense how poor scapulohumeral rhythm could lead to other problems further down the kinematic chain. Let’s say I can’t lift my arms above my head well because I never learned how to use my serratus anterior. I sense that my shoulder hurts if I lift my arm overhead, so to avoid this pain I put my back into extension. (Hypermobile dancers are experts at borrowing spinal movement to achieve upper body positioning.) Over time, I’ll complain of back issues when the problem may very well have started as a shoulder issue owing to poor serratus anterior control.
The lesson here for any strength and conditioning professional or personal trainer is to ensure that our clients are moving well with the most basic movements and intervening with correctives or drill work in between sets. We ought to be teaching our athletes and clients to move well in the gym so that when they need to put themselves into difficult positions outside of the gym their bodies are durable enough to withstand that stress. Our job is NOT to diagnose or treat, but we must bridge the unnecessary divide between prevention and treatment if we believe in developing longterm performance in the people we serve.