Functional subdivision of the upper trapezius muscle during maximal isometric contractions

摘要: The electromyographic (EMG) activity pattern across the upper trapezius of 22 healthy subjects was investigated during maximal isometric contractions. Eight bipolar surface electrodes with 10 mm distance between adjacent electrode pairs were placed on a line from clavicle to scapula. At region near highest EMG amplitudes recorded 90 degrees arm abduction. more posterior parts found both abduction and shoulder elevation. A double differential recording technique which reduced cross-talk contribution supported finding that differently activated when posture changed. normalized amplitude-force relationship elevation showed curvilinear anterior part slower increase in amplitude than force at low force. slope curve, force, increased gradually direction trapezius. patterns indicate flexibility motor activation maybe reflects functional optimization contractions performed by this muscle.