In this diploma thesis I studied magnetic stimulation of skeletal muscles. Measurements were made on the tibialis anterior muscle. The magnetic stimulation was performed by means of TESLA-Stym device (produced by ISKRA MEDICAL d.o.o.). Measurements and tests were performed on 20 healthy volunteers, 11 males and 9 females.
Within the thesis we studied three fields of interest. First, with magnetic stimulation of the tibialis anterior muscle at varying stimulating frequencies of the magnetic field, we observed the generated torque with respect to time. Torque was measured on the foot and it represents the contractions of the tibialis anterior muscle. We were also interested in finding the tetanic frequency. Results show that tetanic frequency varies from individual to individual up to about 5 Hz. We then analysed an individual case and determined the tetanic frequency of the tibialis anterior muscle to be at 40 Hz.
In magnetic stimulation we noticed a wide dispersion of the sizes of muscle responses, although individuals were stimulated with the same signals. We attributed that to physiological and biological differences between individuals and to the principles behind how magnetic muscle stimulation works. We furthermore conclude that the dispersion would be smaller in using electrical stimulation where we would stimulate each individual with the same electric signal.
Second, we compared the size and type of pain between magnetic and electrical stimulation. For this comparison we used McGill pain questionnaire. For information of comparable measurements, where the same muscle was stimulated by means of electrical stimulation, we looked into a related diploma thesis by colleague Miha Sužnik, entitled »Pain evaluation during monophasic and biphasic electrical stimulation«. Results show that magnetic stimulation is less painful than electrical stimulation. Average VAS (visual analog scale - from 0 to 10) pain score for magnetic stimulation was 1,4 and for electrical stimulation, as noted in Miha Sužnik's diploma thesis, 3,4.
We observed that when we stimulated the muscle by means of magnetic stimulation, the experienced pain was directly correlated with the size of muscle response. 8 out of 20 volunteers, which responded to the stimulation with higher muscle response than the other 12, reported on average a 50% higher VAS pain score.
Of 15 descriptors (describing type of pain), only two were reported as more painful in magnetic than in the electrical stimulation: descriptor of tender pain and descriptor of pounding. In electrical stimulation descriptors: piercing, burning and cutting are the most pronounced when compared with magnetic stimulation where they are graded with very low scores. Apart from the mentioned descriptors, two are very pronounced in both magnetic and electrical stimulation. These are shooting and cramping.
Third, we evaluated the maximum capabilities of TESLA-Stym device, by trying to produce the highest muscle contraction possible. We compared the result with the individual's maximal voluntary contraction of the same muscle. On average we recorded that the muscle response we got by means of TESLA-Stym device was 14% of that of the maximal voluntary contraction of the same muscle.