THE EFFECT OF SPINAL POSITION ON SCIATIC NERVE EXCURSION DURING SEATED NEURAL MOBILISATION EXERCISES: AN IN VIVO STUDY USING ULTRASOUND IMAGING

BACKGROUND & OBJECTIVE

Limb and spinal position during seated exercises may influence tension of a peripheral nerve tract and therefore nerve excursion and range of movement (ROM). The aim of this study was to determine whether slump-sitting vs. upright-sitting altered the amount of longitudinal sciatic nerve movement during neural mobilisation exercises. It was hypothesised that exercises performed in slump-sitting would induce less longitudinal sciatic nerve excursion compared to those in upright-sitting due to potentially greater tension being imposed on the sciatic nerve and lumbosacral nerve roots.

METHODS

Passive knee extension was performed on a biodex while positioned in sitting. A knee was passively extended from 90º of flexion until the participant experienced a 4/10 feeling of hamstring stretch discomfort. The slump position was maintained through contact of the sternum against a 45cm diameter ball placed on the participant's lap. The upright-sitting position differed as all participants relaxed into the back-rest of the Biodex. Three movements were performed:

1. Passive knee extension while looking straight ahead
2. Slider mobilisation: passive knee extension and active cervical spine extension from full comfortable cervical flexion to full comfortable cervical extension
3. Tensioner mobilisation: passive knee extension and active cervical flexion from full comfortable cervical extension to full comfortable cervical flexion

For all these exercises, the ankle remained relaxed during the movement of the knee. Longitudinal excursion of the sciatic nerve was measured in millimeters with a blind ultrasound assessment.

RESULTS

Sciatic nerve distal excursion was observed to be slightly greater for upright-sitting compared to slump-sitting, however, this was not significant (P=0.26). Slump sitting position: single-joint mobilization 6.2 mm (slider mobilization 6.4 mm ( 2.7), tensioner mobilization 6.0 mm (2.9). Upright

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