RESUMEN
Spinal manipulation is a manual technique commonly used for the treatment of low back pain. The physiologic mechanisms of spinal manipulation are largely unknown. One basic physiologic response to spinal manipulation [SM] is alternation in Moto neuronal activity, as assessed by the Hoffmann reflex [H-reflex] technique. The purpose of this study was to determine the effect of spinal manipulation on amplitude and onset latency of H-reflexes and on H/M amplitude ratio in patients with low back pain. It was a clinical trial with IRCT201203069222N1 Registration code. Ffifty eight patients with low back pain aged between 20-60 years were included. Tibial nerve H reflex and M wave were recorded before and after Lumbosacral spinal manipulation. The data was analyzed by SPSS 16. Lumbosacral manipulation significantly decrease amplitude of H reflex and H/M amplitude ratio [P<0.05]. It had not significantly effect on H reflex latency or M wave amplitude and latency [P>0.05]. Lumbosacral manipulation produces attenuation of alpha motoneuronal excitability. These findings support of this theory that manual spinal therapy can lead to reduction in muscle tone.