Trapezius Anyone?

As I dive further into my study of the shoulder, its function never ceases to fascinate me. Coming across a study that reflected EMG activity of musculature during over head lifting with stable and unstable loads and surfaces, I found an interesting piece of information that suggests that the role of the trapezius is highly specific .

As their results suggest, increasing resistance using a barbell increases core activation. However, it does not reflect the same linear increase with the trapezius. Their results show little change in the root mean squares and external resistance of 79%, 86% and 89% of the stable surface, stable load lifts - meaning that regardless of load or surface, the trapezius will be firing with the same magnitude during over head lifting. The authors continue to state that the trapezius and it's role as a scapularthoracic (ST) and glenohumeral (GH) stabilizer is specific across all conditions. We also know that the trapezius plays a primary role in scapular elevation and upward rotation during the over head movement, but only after 90 degrees of humeral elevation, yet the forces this muscle has been shown to exert in the study is the same with lighter or heavier loads. In short, we need to condition the trapezius and encourage it's cocontraction with the serratus anterior, rhomboids and other ST stabilizers during rapid limb movement.

Look at it this way:

ST STABILIZERS > GH STABILIZERS > GH LIGAMENTS, CAPSULE & LABRUM

If there is any dysfunction/injury of the ST stabilizers, then the GH stabilizers have to work over time to stabilize the GH joint leading to an altered ball and socket relationship. This can progress to further joint dysfunction, placing increased stress on the ligamentous tissues and possibly pain.