Spinal reflex excitability changes after lumbar spine passive flexion mobilization.
BACKGROUND
Flexion distraction has gained increased credibility as a therapeutic modality for treatment of low back pain. Although important work in the area has elucidated the intradiskal pressure profiles during flexion distraction, the accompanying neural responses have yet to be described.


OBJECTIVE
The purpose of this pilot study was to assess neural reflex responses to motion with 3 degrees of freedom applied to the lumbar spine and to evaluate H-reflex responses of the soleus.


METHODS
Subjects (n = 12) were measured for H-maximum reflexes determined from stimulus response recruitment curves measured in neutral prone position. The mean of 10 evoked H-waves (at H-maximum stimulus intensity) were measured in neutral position, flexion, left and right lateral flexion, and axial rotation of the trunk on an adjusting table. H-reflexes were expressed as a percentage of maximal M-wave for the criterion measure. Spinal range of motion was quantified by digitization.


RESULTS
The data showed variation in some movement ranges, notwithstanding identical table positioning for all subjects. Mean H-reflex amplitude was decreased (15.2 +/- 5.8 mV to 13.8 +/- 5.8 mV), and the H/M ratio was also decreased in flexion compared with neutral (55.0% +/- 19.1% to 50.3% +/- 19.4%; P <.05).


CONCLUSIONS
Trunk flexion is accompanied by inhibition of the motor neuron pool. Slight perturbations in numerous afferent receptors are known to significantly alter the H-reflex. The absence of measurable changes in lateral flexion and trunk rotation may indicate that both slow- and fast-adapting receptors could be involved in lumbar motion. These preliminary findings suggest the need for further dynamic motion studies of the flexion distraction neurophysiologic condition.
Bulbulian
Ronald
R
New York Chiropractic College, Seneca Falls, NY 13148, USA. Rbulbulian@nycc.edu
Burke
Jeanmarie
J
Dishman
J Donald
JD
D000328:Adult; D005260:Female; D006181:H-Reflex; D006801:Humans; D007537:Isometric Contraction; D017116:Low Back Pain / Q000503:physiopathology* / Q000628:therapy*; D008159:Lumbar Vertebrae / Q000503:physiopathology*; D008297:Male; D020393:Manipulation, Spinal / Q000379:methods*; D009119:Muscle Contraction; D010865:Pilot Projects; D016684:Prone Position; D016059:Range of Motion, Articular