Effect of cervical spinal adjustments on lumbar paraspinal muscle tone: evidence for facilitation of intersegmental tonic neck reflexes.

OBJECTIVES: To determine whether spinal adjustments, delivered to the upper vs. lower cervical spine, might result in tonic neck reflex-induced alterations in the activity of the lumbar paraspinal musculature.

DESIGN: Randomized, double-blind, before/after treatment comparisons.

SETTING: Cervical Ergonomics Laboratory, Palmer College of Chiropractic-West, Sunnyvale, CA.

SUBJECTS: Healthy, nonsymptomatic chiropractic college students, about evenly divided with respect to gender and ranging from 23-38 yr of age.

INTERVENTION: Modified "diversified" spinal adjustments, delivered bilaterally to either the upper (C2) or lower (C7) cervical region.

MAIN OUTCOME MEASURE: Tissue compliance measures using a tissue compliance meter, obtained from each subject at sites 2 cm on either side of the spinous processes of L1, L2, L3, L4 and L5 both prior to and within 15 min following treatments.

RESULTS: Upper cervical adjustments produced changes in lumbar tissue compliance which were only slight (p < .05) and not significantly different from that which occurred following upper cervical sham manipulation (p > .1). However, lower cervical adjustments induced increases in tissue compliance (decreases in tone) which were highly significant (p < .001) and relatively robust compared to those found following upper cervical adjustments (p < .01). Furthermore, the greatest effects were observed on either side of the L4 and L5 spinous processes, suggesting influences on the gluteal musculature in particular.

CONCLUSIONS: Results indicate that cervical spinal manipulation can have significant effects on the tone of the lumbopelvic musculature, presumably by facilitating tonic neck reflexes involving intersegmental spinal pathways.