We studied the influence of various parameters of high-frequency nanosecond pulse bursts
on the strength of rabbit muscle contractions. Ten unipolar high-frequency pulse bursts
with various field intensities E (1 kV/cm, 4 kV/cm, and 8 kV/cm), intraburst frequencies f
(10 kHz, 100 kHz, and 1 MHz), and intraburst pulse numbers N (1, 10, and 100) were applied
using a pair of plate electrodes to the surface skin of the rabbits’ biceps femoris, and
the acceleration signal of muscle contraction near the electrode was measured using a
3-axis acceleration sensor. A time- and frequency-domain analysis of the acceleration
signals showed that the peak value of the signal increases with the increasing strength of
the pulse burst and that the frequency spectra of the signals measured under various pulse
bursts have characteristic frequencies (at approximately 2 Hz, 32 Hz, 45 Hz, and 55 Hz).
Furthermore, we processed the data through multivariate nonlinear regression analysis and
variance analysis and determined that the peak value of the signal scales with the
logarithm to the base 10 of ENx, where x is a value that scales with the logarithm to the base
10 of intraburst frequency (f). These results indicate that for high-frequency nanosecond
pulse treatment of solid tumors in or near muscles, when the field strength is relatively
high, the intraburst frequency and the intraburst pulse number require appropriate
selection to limit the strength of muscle contraction as much as possible.