Spinal reflex excitability changes after cervical and lumbar spinal manipulation: a comparative study.
BACKGROUND
Spinal manipulation (SM) is a commonly employed nonoperative treatment modality in the management of patients with neck, low back or pelvic pain. One basic physiologic response to SM is a transient decrease in motoneuron activity as assessed using the Hoffmann reflex (H-reflex) technique. Previous research from our laboratory indicates that both SM with a high-velocity, low-amplitude thrust and mobilization without thrust produced a profound but transient attenuation of motoneuronal activity of the lumbosacral spine in asymptomatic subjects. To date, effects of cervical SM procedures on the excitability cervical motoneuron pools are unknown.


OBJECTIVE
The objective of this research was to a gain a more complete understanding of the physiologic effects of SM procedures on motoneuron activity, by comparing the effects of regional SM on cervical and lumbar motoneuron pool excitability.


METHODS
Maximal H-reflex amplitudes were recorded before and after SM in both the cervical and lumbar regions of asymptomatic subjects in two successive experimental sessions.


METHODS
Asymptomatic, young healthy volunteers were used in this study.


METHODS
Changes in flexor carpi radialis and gastrocnemius H-reflex amplitudes before and after SM procedures.


METHODS
H-reflexes recorded form the tibial and median nerves were evaluated before and after lumbar and cervical SM, respectively.


RESULTS
Both Lumbar and cervical SM produced a transient but significant attenuation of motoneuron excitability. The attenuation of the tibial nerve H-reflex amplitude was proportionately greater than that of the median nerve, which occurred after cervical SM.


CONCLUSIONS
SM procedures lead to transient suppression of motoneuron excitability, as assessed by the H-reflex technique. Lumbar spine SM appears to lead to greater attenuation of motoneuron activity compared with that of the cervical region. Thus, these two distinct regions of the spine may possess different responsiveness levels to spinal manipulative therapy.
Dishman
J Donald
JD
Department of Anatomy, New York Chiropractic College, 2360 SR 89, Seneca Falls, NY 13148, USA. ddishman@nycc.edu
Burke
Jeanmarie
J
D000328:Adult; D002574:Cervical Vertebrae; D004558:Electric Stimulation; D004576:Electromyography; D006181:H-Reflex; D006801:Humans; D008159:Lumbar Vertebrae; D020393:Manipulation, Spinal; D008475:Median Nerve / Q000502:physiology; D009046:Motor Neurons / Q000502:physiology; D012016:Reference Values; D013116:Spinal Cord / Q000502:physiology*; D013979:Tibial Nerve / Q000502:physiology; D013997:Time Factors