Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 56 10 2019 01 13 671 676 EN Mohaddeseh Azadvari Department of Physical Medicine and Rehabilitation, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran. Seyede Zahra Emami Razavi Department of Physical Medicine and Rehabilitation, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran. Farid Rezaiee-Moghaddam Department of Physical Medicine and Rehabilitation, Emam Reza Hospital, Aja University of Medical Sciences, Tehran, Iran. Zahra Reza-Soltani Department of Physical Medicine and Rehabilitation, Emam Reza Hospital, Aja University of Medical Sciences, Tehran, Iran. Sirus Azizi Department of Physical Medicine and Rehabilitation, Emam Reza Hospital, Aja University of Medical Sciences, Tehran, Iran. Amir Rakhshan Department of Foreign Languages, Tehran University of Medical Sciences, Tehran, Iran. 2017 12 20 2018 11 14 Spinal manipulation is a manual technique commonly used for the treatment of low back pain. The physiologic mechanisms of the spinal manipulation are largely unknown. One basic physiologic response for spinal manipulation is an alteration in motoneuronal activity, as assessed by the Hoffmann reflex (H-reflex) technique. The purpose of this study was to determine the effect of spinal manipulation on the amplitude and onset latency of H-reflex and on H/M amplitude ratio in patients with low back pain. Fifty-Eight patients with low back pain aged between 20-60 years, who had no exclusion criteria were included. Tibial nerve H-reflex and M wave were recorded before and after Lumbosacral spinal manipulation. Lumbosacral manipulation significantly decreased the amplitude of the H-reflex and H/M amplitude ratio (P<0.05). It had no significant 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 this theory that manual spinal therapy can lead to a reduction in muscle tone. https://acta.tums.ac.ir/index.php/acta/article/view/6902 https://acta.tums.ac.ir/index.php/acta/article/download/6902/5173