New method using multi-regression analysis on evoked electromyography during movement to adjust stimulation conditions.

A new method of stimulation of the lower extremities was devised that automatically adjusts the stimulation conditions at any angle of the knee joint. An M-wave is considered to indicate the stimulation conditions, because it is the waveform that results from direct stimulation to the axon of the alpha motor neuron. The present device adjusted the stimulation intensity, using multi-regression analysis to evoke an M-wave of preset amplitude. Participants included five people without any neuromuscular impairment. The subjects sat on a chair during the test. The hip joint was fixed at a flexion angle of 90 degrees, and the ankle joint was fixed at the midposition. During passive knee joint movement ranging from 0 degrees to 135 degrees, M-waves were measured. Electrodes were attached at the popliteal fossa and the patella to stimulate the tibial nerve. Ag-AgCl electrodes were put on the belly of the right soleus muscle for the M-wave measurement. The device was set to give M-waves close to the preset value, 10% Mmax. According to previous research, the allowable limit of M-wave amplitude deviations was reported to be about 5% Mmax. The M-wave amplitudes evoked by the device were in the allowable range (9.2 +/- 2.5% Mmax). The device enabled control of the M-wave amplitude over the entire range of motion of the joint. Using this device, it was possible to examine the excitability of the alpha motor neuron pool more precisely.