Any movement combines stability and mobility. Stability is not usually absolute. It may mean an area of the body will be held still or move through a controlled pattern during a certain part of an action. When we blend stability and mobility, we are able to control the movement of different body parts, simultaneously holding still and allowing movement where appropriate.
A good example of blending steadiness and movement is the stable platform the shoulder blade provides when moving the arm. Without the stability of the shoulder blades, the upper extremities are at risk of injury during movement. This need for a stable platform has sometimes been misinterpreted as need for the shoulder blades to be held statically. This is not true. You should be able to control the shoulder blades when you are doing activities that involve the upper extremities without holding them rigidly in one position. For example, during yoga class it is often said that the shoulder blades should be held down and in. That is fine for early movements of the upper extremities, but once the arm is a bit below shoulder height, the shoulder needs to move and rotate. Otherwise the bone of the upper arm (humerus) and the tip of the shoulder (acromion) will bump into each other, pinching tendons that run between the shoulder blade and arm.
It is easy to see where an instruction like this has come from. Many people habitually use their upper trapezius when they raise their arms, which causes the shoulders to lift toward the ears. This elevates the shoulder blades and locks them in a position that prevents rotation as the arms are lifted, possibly leading to a shoulder impingement. So keeping the shoulder blades down and in is a well-meant instruction and appropriate for the early stages of the movement, but not for the later aspect of raising the arms overhead. The following movement exploration demonstrates the distinction in quality of movement.
Stability and Mobility
- Try to lift your arms out to the sides and up overhead while at the same time using the upper trapezius to lift your shoulders toward your ears. Comfortable? Not likely.
- Repeat, but this time with the shoulder blades held down and in. That is not very comfortable either because neither of these variations allow the shoulder blades to participate in the rhythm of the movement.
- Now stabilize your shoulder blades down and in, lift your arms straight out to about 60 degrees, then allow your shoulder blades to participate in the movement as you continue to lift your arms overhead. Can you feel how you started lifting your arms from a stable platform (shoulder blades) and then allowed movement to occur in the shoulder blades? This is a good example of the blend of stability and mobility that is a characteristic of good movement: controlling the movement of different body parts, stabilizing, and allowing movement to occur as needed.