Introduction: Spinal manipulative treatment is widely used among manual therapists, although knowledge regarding the absolute physiological effects has not been clearly established. In this study, 20 healthy male subjects underwent a unilateral high-velocity low-amplitude thrust (HVLAT) to the lumbosacral junction, while the cutaneous blood flow in the corresponding dermatome of the lower limb was monitored.

Methods: Subjects underwent a sham manipulation before the actual manipulation and acted as their own control. Laser Doppler flowmetry was used to measure relative changes in the cutaneous blood flow over the L5 dermatome for 5 minutes before the sham manipulation, for 5 minutes between the sham and the actual manipulation, and for 5 minutes after the spinal adjustment. Analysis of variance (ANOVA) and Tukey post hoc analysis was used in the interpretation of the data.

Results: Twelve nonsmoking subjects, who received a successful HVLAT manipulation, showed a significant increase (P <.001) in blood perfusion, both ipsilaterally and contralaterally. Six smokers responded with a significant decrease in blood flow ipsilaterally (P <.01) and contralaterally (P <.001) after HVLAT manipulation.

Conclusion: The results from this study support previous published hypotheses that spinal adjustments outside the region of the sympathetic outflow result in an increase in cutaneous blood flow. Further studies will be needed to confirm the outcome of this study, and more knowledge is needed regarding the specific neurophysiological effects of spinal manipulation.