Adverse mechanical tension in the nervous system? Analysis of straight leg raise

Abstract

The aim of this study was to investigate the effects of ankle dorsiflexion and cervical spine flexion on compliance of neural tissues to the straight leg raise (SLR) test in 20 normal subjects and 20 age and sex matched subjects with lumbar or sacral radiculopathy. Measures taken during SLR were SLR range at onset of resistance (R1) determined by an examiner, range of SLR at first increase in moment of the stretched tissues (M r ), and M r through range of SLR before and after onset of muscle activity (M1) recorded by electromyo-graphy. Results indicated that R1, although reliable, bares no correlation with measures of compliance and therefore has no discriminative power or validity. Ankle dorsiflexion and cervical spine flexion had insignificant effects on M r . However, M r was significantly greater in the radiculopathy group in SLR range post but not pre-M1. These results demonstrate normal compliance of neural tissue in subjects who present with adverse responses to, what has been referred to as, neural tension tests. We therefore recommend the term tension test be abandoned as it does not reflect the true nature of neural pathophysiology. Rather than R1 and through range resistance we suggest M1 more accurately represents increased neural mechanosensitivity and therefore clinically it is a more useful measure of neural pathophysiology.