Tactile Perception of Pressure and Volitional Thrust Intensity Modulate Spinal Manipulation Dose Characteristics.

OBJECTIVE:The purpose of this study was to examine clinicians' ability to modulate spinal manipulation (SM) thrust characteristics based on their tactile perception of pressure and volitional intensity. METHODS:In a cross-sectional, within-participants design, 13 doctors of chiropractic delivered SM thrusts of perceived least, appropriate, or greatest intensity of their perceived safe output level for an SM thrust on low-fidelity thoracic spine models of 4 different pressure levels. The participants performed SM over the course of 96 trials in a randomized order on combinations of thrust intensity and pressure. Dependent variables included normalized preload force, thrust force, thrust duration, peak acceleration, time to peak acceleration, and displacement. For all dependent measures, 2-factor within-participants analysis of variance models with repeated measures on both factors were performed. RESULTS:Preload force increased with intensity (F2,24 = 9.72; P < .001) and model pressure (F3,36 = 4.27; P = .011). Participants modulated thrust force and displacement as each also increased with intensity escalation (F2,24 = 22.53, P < .001; F2,18 = 45.20, P < .001). The highest accelerations were observed during the greatest intensity. Increased thrust force was delivered at higher model pressures (F3,36 = 6.43; P < .001). A significant interaction demonstrated that as volitional thrust intensity increased, greater displacement was attained, particularly on low pressure models (F6,54 = 11.06; P < .001). Thrust duration and time to peak acceleration yielded no significant differences. CONCLUSION:Spinal manipulation thrust dosage was modulated by the chiropractors' tactile perception of pressure and volitional intensity.