How Spinal Manipulation Affects Motor Neuron Excitability
The physiologic mechanisms involved in spinal manipulative therapy and massage therapy are largely unknown. One hypothesis poses that spinal manipulation inhibits alpha motoneuron activity. Based upon this premise, this study compared the magnitude and duration of motoneuron inhibition following spinal manipulation compared to massage of the paraspinal and limb muscles.
Fifteen asymptomatic volunteers were randomly assigned to one of three groups: spinal manipulation, massage, or control group.
Baseline tibial nerve H-reflex amplitudes were measured prior to the application of lumbosacral spinal manipulation or paralumbar and limb massage. Post-interventional H-reflex recordings were recorded immediately following the application of either modality.
The results showed that spinal manipulation significantly attenuated alpha motoneural activity immediately post-therapy, as measured by the amplitude of the tibial nerve H-reflex. Paraspinal and limb massage did not inhibit the motoneuron pool as measured immediately post-therapy.
These findings support the hypothesis that spinal manipulation procedures lead to short-term inhibitory effects on motoneuron excitability to a greater magnitude than massage. This study takes us one step closer to understanding the physiologic mechanism involved in spinal manipulative therapy.
Dishman JD, Bulbulian R. Comparison of effects of spinal manipulation and massage on motoneuron excitability. Electromyographic Clinical Neurophysiology
2001:41, pp. 97-106.