Wednesday, December 16, 2009

Effect of eye position on neck muscle activity

Dominant eye assessment has been an integral part of spine conditions especially to reason out the spinal asymmetry.

Activity of splenius capitis (SC) is modified with gaze shift. Further, control of the neck muscles is coordinated with the sensory organs of vision, hearing and balance.

Impact of eye movement on cervical muscles & movements are not much studied in the context of management of cervical dysfunctions. we can pick up some clues from the study below:

The following is a study of division of physiotherapy (University of Queensland, Australia) which investigates interaction between eye movement and neck muscle activity in influencing the control of neck movement.

The effect of eye position on neck muscle activity during cervical rotation was studied on 11 subjects. Muscles to rt. Side cervical rotation (in sitting) was under real-time EMG surveillance i.e. right obliquus capitis inferior (OI), multifides (MF), and splenius capitis (SC), and left sternocleidomastoid (SCM). The cervical rotation was carried out with a fixed infra-orbital position.

The results show:

1. Right SC and left SCM EMG increased with rotation to the right, contrary to anatomical texts.
2. OI EMG increased with both directions
3. MF EMG did not change from the activity recorded at rest.

This study also shows during neck rotation SCM and MF EMG was less when the eyes were maintained with a constant intra-orbit position that was opposite to the direction of rotation compared to trials in which the eyes were maintained in the same direction as the head movement.
Hence the inter-relationship between eye position and neck muscle activity may affect the control of neck posture and movement.

Bexander, Mellor & Hodges; Exp Brain Res. Effect of gaze direction on neck muscle activity during cervical rotation 2005 Dec;167(3):422-32. Epub 2005 Sep 29.

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