Effect of straight leg raise examination and treatment on vibration thresholds in the lower limb: a pilot study in asymptomatic subjects

Individuals who participate in repetitive functional activities may have alteration in large diameter neural activity. It has been proposed that neurodynamic examination and treatment may affect large diameter afferent activity, and that neurological integrity tests should be carried out prior to neurodynamic testing. Vibration threshold testing (VTT) has been shown to be a valid measure of large diameter afferent conduction. The aim of this study was to assess whether examination and treatment of straight leg raise with plantar flexion and inversion (SLR) has an effect on the conduction of large diameter afferents supplying the lower leg in normal subjects and in a group of runners. Twenty sedentary asymptomatic subjects and 10 asymptomatic runners underwent VTT at the second and fourth metatarsals (representing the distribution of the superficial peroneal nerve) before and after examination of the SLR and after a mimicked treatment with SLR (VTT carried out immediately and 10 min after treatment). A repeated measures ANOVA revealed no significant baseline differences in VT between runners and non-runners (P=0.171), or between any of the four test conditions in either group (P=0.5). Although not significant there was a trend for runners to have raised mean VT compared to non-runners, and for SLR treatment to cause an elevation in VT in both groups. These results suggest that examination and treatment of SLR may not be detrimental to function of the large diameter afferents in asymptomatic subjects.