Acute Effects of Manual vs Instrument-assisted Single Cervical Manipulation on Electromyographic Activity and Sympathetic Nervous System

The manual manipulation was applied over C3/C4, as the participants were positioned in supine with the cervical spine in a neutral position. Slight ipsilateral side flexion and contralateral rotation were introduced until tension was perceived in the tissues at the contact point. A high-velocity, low-amplitude thrust manipulation was directed upward and medially in the direction of the subject's contralateral eye.

The instrument-assisted manipulation was applied using a handheld Activator IV Adjusting Instrument. Contacts were made firm enough to prevent slipping of the rubber tip but not so firm as to load the spring, in consistence with customary clinical use of the instrument. The spring was then loaded by means of the instrument's trigger mechanism, and the impulse was delivered in an anterosuperior direction, over the posterolateral aspect of the vertebra on the right lamina-pedicle junction of C3.

The sham manipulation to the right C3/C4 segment was administered using the same 'set-up' as for the manual manipulation; however, once the barrier was engaged, the head was re-positioned to neutral with no thrust applied. The control group individuals were positioned supine for the same twenty minutes as the other groups and they received no manual contact.