Difference in the Electromyographic Onset of the Deep and Superficial Multifidus during Shoulder Movements in Different Standing Positions in the Frontal Plane

Abstract

[Purpose] The present study examined the electromyographic onset of the lumbar multifidus during shoulder flexion and extension and investigated the influence of standing position with different pelvic alignments in the frontal plane before arm movement. [Subjects and Methods] Intramuscular and surface electrodes recorded the electromyographic onset of the deep fibers of the lumbar multifidus (DM), and the superficial fibers of the multifidus (SM), anterior deltoid and posterior deltoid. Nine healthy participants performed rapid, unilateral shoulder flexion in response to audio stimuli in three standing positions: quiet standing, left pelvis dropped position, and left pelvis raised position. [Results] Repeated two-way analysis of variance found that the main effect of the standing position was significant when shoulder flexion was performed. No interaction was detected between standing position and muscles. [Conclusion] These results suggest that the electromyographic onsets of DM and SM are influenced by standing position with different pelvic alignments in the frontal position.