Clinical NeuroscienceUnderstanding inhibitory mechanisms of lumbar spinal manipulation using H-reflex and F-wave responses: A methodological approach

The purpose of this research was to characterize unique neurophysiologic events following a high velocity, low amplitude (HVLA) spinal manipulation (SM) procedure. Descriptive time series analysis techniques of time plots, outlier detection and autocorrelation functions were applied to time series of tibial nerve H-reflexes that were evoked at 10-s intervals from 100 s before the event until 100 s after three distinct events L5-S1 HVLA SM, or a L5-S1 joint pre-loading procedure, or the control condition. Sixty-six subjects were randomly assigned to three procedures, i.e., 22 time series per group. If the detection of outliers and correlograms revealed a pattern of non-randomness that was only time-locked to a single, specific event in the normalized time series, then an experimental effect would be inferred beyond the inherent variability of H-reflex responses. Tibial nerve F-wave responses were included to determine if any new information about central nervous function following a HVLA SM procedure could be ascertained. Time series analyses of Hmax/Mmax ratios, pre-post L5-S1 HVLA SM, substantiated the hypothesis that the specific aspects of the manipulative thrust lead to a greater attenuation of the Hmax/Mmax ratio as compared to the non-specific aspects related to the postural perturbation and joint pre-loading. The attenuation of the Hmax/Mmax ratio following the HVLA SM procedure was reliable and may hold promise as a translational tool to measure the consistency and accuracy of protocol implementation involving SM in clinical trials research. F-wave responses were not sensitive to mechanical perturbations of the lumbar spine.

► H-reflex is reliably attenuated following spinal manipulation. ► H-reflex attenuation is sensitive and unique to manipulation. ► H-reflex is a reliable index of motor neuron excitability. ► F-wave responses are not sensitive to mechanical perturbation of the spine.