For purposes of this study, we have broken the force of adjustment into two parts. It is a reaction force because the harder the tissue pushes back of it, the greater will be the measured stylus force. The second part is the force between the stylus and the neck tissues during the thrust. This variable is more complicated, as the force applied is really a function of the tissue into which the stylus is moving. Its value is continually changing during the thrust as the stylus encounters increasing tissue resistance.
Stylus force becomes therefore a function of stylus excursion, i.e., location.
The greater the excursion, the greater the force. For this reason, we have opted to control excursion in this experiment while monitoring the stylus force. Most adjusting techniques, both hand and instrument, use rapid thrusts such as this with comparable durations. Participation is contingent upon passage of the clinic physical and signing an informed consent. The experiment itself basically involves assessing each subject by x-ray, leg check, and palpation, adjusting and then reassessing.