The effect of lumbosacral manipulation on corticospinal and spinal reflex excitability on asymptomatic participants.
OBJECTIVE
The aim of the study was to examine the effects of a high-velocity, low-amplitude (HVLA) manipulation to the lumbosacral joint on corticospinal excitability, as measured by motor evoked potentials (MEPs) using transcranial magnetic stimulation, and spinal reflex excitability, as measured by the Hoffman reflex (H-reflex).


METHODS
In a randomized, controlled, crossover design, 14 asymptomatic volunteers (mean age, 23 ± 5.4 years; 10 men; 4 women) were measured for MEPs and H-reflexes immediately before and after a randomly allocated intervention. The interventions consisted of HVLA applied bilaterally to the lumbosacral joint and a control intervention. Participants returned a week later, and the same procedures were performed using the other intervention. Data for H-reflex and MEP amplitudes were normalized to the M-wave maximum amplitude and analyzed using 2-way analysis of variance with repeated measures.


RESULTS
A significant interaction of treatment by time was found for MEP (F(1,13) = 4.87, P = .04), and post hoc analyses showed that the MEP/M-wave maximum ratio decreased significantly in the HVLA treatment (P = .02; effect size, 0.68). For H-reflex, there was a significant effect of time (F(1,13) = 8.186, P = .01) and treatment and time interaction (F(1,13) = 9.05, P = .01), with post hoc analyses showing that H-reflexes were significantly reduced after the HVLA manipulation (P = .004; effect size, 0.94). There were no significant changes in MEP latency or silent period duration.


CONCLUSIONS
An HVLA manipulation applied to the lumbosacral joint produced a significant decrease in corticospinal and spinal reflex excitability, and no significant change occurred after the control intervention. The changes in H-reflexes were larger than those in MEPs, suggesting a greater degree of inhibition at the level of the spinal cord.
School of Biomedical and Clinical Sciences and Institute of Sport, Exercise and Active Living, Victoria University, Melbourne, Australia. gary.fryer@vu.edu.au
Gary
G
Fryer
Alan J
AJ
Pearce
D000293:Adolescent; D000328:Adult; D018592:Cross-Over Studies; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D008161:Lumbosacral Region; D008297:Male; D020393:Manipulation, Spinal / Q000379:methods*; D011712:Pyramidal Tracts / Q000502:physiology; D012016:Reference Values; D050781:Transcranial Magnetic Stimulation / Q000379:methods*; D016896:Treatment Outcome; D055815:Young Adult