Lower Trapezius: The Key to Scapula Control?

The lower trapezius is a muscle that is proposed to play an important role in ‘ideal’ scapula mechanics. It is agreed that poor scapula movement (scapula dyskinesis) during overhead activities may predispose the athletic shoulder to injury in the form of impingement, subacromial bursitis and instability^{(1, 2, 3)}. Due to the role it plays in scapula function and subsequent athletic shoulder pain, the lower trapezius has received a lot of interest, regarding both its activation ratios against the other trapezius as well as its timing during movement^{(4, 5, 6, 7)}.

Anatomy

Surprisingly, very little academic research has been conducted on the exact anatomy of the lower trapezius. There is however a plethora of research regarding the role of the lower trapezius in scapula function and the association between lower trapezius dysfunction and shoulder pain. The most notable research piece on the anatomy of the lower trapezius was only conducted relatively recently in 1994 by Johnson et al⁽⁸⁾. They found that the lower trapezius originates on the spine and extends from T2 to T12 and inserts onto the spine of the scapula from the acromion process to its root. It is closely aligned to the middle trapezius which attaches to the C7 and T1 vertebrae, and this also attaches to the spine of the scapula. It is a multipennate muscle that is innervated by the accessory nerve and the ventral rami of the third and fourth cervical nerves via the cervical plexus (see figures 1 and 2⁽⁹⁾).