Effect of Neck Rotation on Limb Position Sense

Abstract

Position sense of limb muscles depends mainly on afferent discharges of muscle spindles. Enhanced or attenuated afferent discharges of muscle spindles can lead to limb position sense errors. Neck rotation produces reflexes that arise from receptors in the region of the upper cervical joints and changes the activity of limb muscles. Stimulation of the neck receptors increases H-reflex amplitude of limb muscles in the ipsilateral side and decreases it in the contralateral side. The aim of the present study was to examine whether changes in neck position cause limb position sense errors in humans. Experiments were performed in 8 healthy men. Subjects were seated on a chair and placed both their forearms on a table in front of them. The forearms were lifted to an angle of 90 degrees by an assistant, and subjects were asked to rotate the neck to the right or left side. The right arm was then lowered to an angle of 30 degrees, and the subjects were asked to match the left arm position with the right arm. With right rotation of the neck, subjects placed their left forearms in a more flexed position than the right forearms; with left rotation, they placed their left forearms in a more extended position. We conclude that rotation of the neck produced limb position sense errors, and that the direction of the rotation was a determinant of what error appears.