Background: Peripheral skin blood flow (SBF) changes during and after spinal mobilization (SM), evaluated with laser Doppler flowmetry, may document physiological responses associated with SM.

Objectives: To document variations in SBF during and after application of an SM and evaluate influence of pressure on SBF by applying the same standardized SM with 3 different nonnoxious pressures.

Design: Cross-over design with 4 interventions on 4 different days: control (no touch) and 3 SMs applied rhythmically at 5%, 40%, or 80% of pain pressure threshold (sham SM, low-pressure SM, or high-pressure SM, respectively).

Method: Thirty-two individuals participated. The inspiratory gasp (IG) test was our positive control of vasoconstriction through excitation of the skin sympathetic nervous activity (SSNA). Each session comprised 5 phases: (1) baseline at the end of a 20-min acclimatization, (2) IG test, (3) post-IG phase, (4) SM phase or no manual contact for control, and (5) post-SM phase. A Biopac MP36 system collected SBF data, and a Novel Pliance-X system recorded pressure data.

Results/findings: Equal and significant bilateral vasodilation occurred during application of unilateral sham SM, low-pressure SM, and high-pressure SM. Post-SM significant vasodilation persisted after high-pressure SM.

Conclusions: The current study is the first to describe bilateral peripheral SBF changes occurring during and 5 min after application of standardized SMs. Our post-SM vasodilation suggests involvement of mechanisms other than the putative SSNA-excitatory mechanism proposed with skin conductance measurements. Persistence of post-SM vasodilation following only high-pressure SM suggests possible pressure-dependent mechanisms. However, further research is warranted to clarify our findings.