Recently I've held a few workshops for a group of personal trainers and personal training students on shoulder function with a focus on scapulothoracic (ST) stability. After reflecting on my presentation and the many great questions that were asked, I wanted to find a simplistic way to approach a very complicated joint by addressing three concepts. Here they are:
FORCE COUPLES
By understanding the muscles that create a "pull" on a bone or joint, we can better understand its role as a stabilizer or mobilizer. In reference to the ST joint, the trapezius, serratus anterior, rhomboids, pectoralis minor and biceps brachii all have attachments to the scapula and pull in different directions to ensure proper joint kinematics - or "force-couple relationship".Humphery, 2004 discussed how important the force-couple relationshipo of the ST joint as being the "hinge for all functional strength and power". Below is an example of the trapezius and serratus anterior force-couple relationship.
PLANES OF MOTION
Multi-planar movement is a staple of every day life, rehabilitation and athletic development.Oyama, et. al., 2010 compared three-dimensional scapular kinematics during 6 scapular retraction exercises and found that all involved the force couple relationships of the trapezius and serratus anterior and encouraged posterior tipping, lateral rotation and depression of the ST joint - this is of great significance as I believe this will allow the scapula to rest properly upon the posterior thoracic cage at the desired 35-40 degrees which sets the client up for good posture statically and dynamically. Below is a diagram of the three planes of motion of the ST joint.
STABILITY WITH RAPID LIMB MOVEMENT
Planks are great - but we need to get away from ONLY implementing static stability exercises. This is where I believe many fitness professionals become stagnant. "Stability" has almost become the buzz word within the fitness world, but what does it really mean? Stability can best be defined as the ability to control force. These forces that are applied to tissues can originate inside or outside the body - think biomechanics & physics.
Our goal should be to prescribe a progessional training regimine that will allow our clients to improve static stability using isometric and reduced tempo movements with the intent of encouraging the same joint stability during rapid limb movement. In this article, Roy, et. al., 2009 shows a short term improvement with rehabilitating impingement syndrome patients gaining almost immediate benefit by changing the magnitude of forces and incorporating limb movement. Limb movement in this study was performed at "normal daily task" tempo - however, this definitely sets the stage for further investigation and theory that rapid limb movement can further encourage joint stability. In short, moving the arms rapidly can be a viable progression in improving ST dynamic stability - particularly during upward rotation.
Check out this exercise next time you're in the gym!
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