Pressure Pain Thresholds and Basal Electromyographic Activities Following Spinal Mechanical Manipulation

Subjects in experimental group are assessed through use of the Activator Methods (AM) assessment protocol. Spinal adjustment of the indicated pelvis, sacrum and lumbar spine is performed through the use of spinal mechanical manipulation. In this study leg length analysis only uses Position #1 and Position #2. Mechanical manipulation is delivered with the Activator Ⅳ Adjusting Instrument (AAI Ⅳ; Activator Methods International, Ltd, Phoenix, AZ) set in the maximal force setting 4, as it is used in routine clinical practice. The Activator Ⅳ delivers a very short duration (\<5 ms) force-time impulse with a peak force magnitude of approximately 176N.

Subjects in the control group receive a protocol identical to that described above, with the following exception: a sham mechanical thrust is delivered during the AM protocol. The sham procedure is accomplished by setting the expansion control knob on the Activator Ⅱ to the zero (off) position. The expansion control is used to adjust the spring compression and thus the amount of excursion of the instruments' stylus. In the zero position, no excursion of the stylus occurs, although the same clicking sound that the instrument produces during normal use is heard after manual activation of the mechanical trigger.