Citation

Röijezon U, Jull G, Djupsjöbacka M, Salomoni SE, Hodges PW. Hum. Mov. Sci. 2021; 80: e102893.

Copyright

(Copyright © 2021, Elsevier Publishing)

DOI

10.1016/j.humov.2021.102893

PMID

34763288

Abstract

Biomechanical modelling and physiological studies suggest that various spinal muscle layers differ in their contribution to spine movement and stiffness. This study aimed to investigate the activation of deep and superficial muscles in stable and unstable task conditions. Nine healthy participants performed a task of controlling a metal ball on a plate fixed to the head in seated position. In unstable tasks, visual feedback was provided by mirrors to move the ball to the centre of the plate by small head movements and maintain the position for 3 s. Task difficulty was adjusted in a stepwise progression of difficulty using five surfaces with materials of decreasing resistance. In the stable condition, the ball was fixed to the plate's centre. EMG was recorded with surface (sternocleidomastoid, anterior scalenes, upper trapezius) and fine-wire electrodes (rectus capitis posterior major, obliquus inferior, multifidus, semispinalis cervicis, splenius capitis). The outcome variable was root mean square (RMS) EMG during the part of the task when the ball was maintained in the centre position.

RESULTS revealed greater cervical muscle activity in the unstable than stable conditions (p < 0.001, η(p)(2) = 0.746). Control of deep and superficial cervical muscles differed (p = 0.003, η(p)(2) = 0.354). Deep cervical muscle activity was greater with unstable tasks, but did not differ with task difficulty. In contrast, superficial cervical muscle activity increased in a stepwise manner with increasing challenge. These results support the notion that the central nervous system uses different strategies for control of deep versus superficial muscle layers of the cervical spine in association with instability.

Language: en

Keywords

Postural control; Electromyography; Motor task; Neck muscles; Unstable system