title: Estimation of the distribution of intramuscular current during electrical stimulation of the quadriceps muscle.
abstract: Electrical stimulation is commonly used for strengthening muscle but little evidence exists as to the optimal electrode size, waveform, or frequency to apply. Three male and three female subjects (22-40 years old) were examined during electrical stimulation of the quadriceps muscle. Two self adhesive electrode sizes were examined, 2 cm x 2 cm and 2 cm x 4 cm. Electrical stimulation was applied with square and sine waveforms, currents of 5, 10 and 15 mA, and pulse widths of 100-500 micros above the quadriceps muscle. Frequencies of stimulation were 20, 30, and 50 Hz. Current on the skin above the quadriceps muscle was measured with surface electrodes at five positions and at three positions with needle electrodes in the same muscle. Altering pulse width in the range of 100-500 micros, the frequency over a range of 20-50 Hz, or current from 5 to 15 mA had no effect on current dispersion either in the skin or within muscle. In contrast, the distance separating the electrodes caused large changes in current dispersion on the skin or into muscle. The most significant finding in the present investigation was that, while on the surface of the skin current dispersion was not different between sine and square wave stimulation, significantly more current was transferred deep in the muscle with sine versus square wave stimulation. The use of sine wave stimulation with electrode separation distances of less then 15 cm is recommended for electrical stimulation with a sine wave to achieve deep muscle stimulation.
authors.affiliation: Department of Physical Therapy, Loma Linda University, Loma Linda, CA 92350, USA. jpetrofsky@llu.edu
authors.forename: Jerrold
authors.initials: J
authors.lastname: Petrofsky
authors.forename: Michelle
authors.initials: M
authors.lastname: Prowse
authors.forename: Melanie
authors.initials: M
authors.lastname: Bain
authors.forename: Elaine
authors.initials: E
authors.lastname: Ebilane
authors.forename: Hye Jin
authors.initials: HJ
authors.lastname: Suh
authors.forename: Jennifer
authors.initials: J
authors.lastname: Batt
authors.forename: Daryl
authors.initials: D
authors.lastname: Lawson
authors.forename: Viviana
authors.initials: V
authors.lastname: Hernandez
authors.forename: Armia
authors.initials: A
authors.lastname: Abdo
authors.forename: Tien-Ning
authors.initials: TN
authors.lastname: Yang
authors.forename: Enrique
authors.initials: E
authors.lastname: Mendoza
authors.forename: Kelly
authors.initials: K
authors.lastname: Collins
authors.forename: Michael
authors.initials: M
authors.lastname: Laymon
mesh_terms: D000328:Adult; D004599:Electric Stimulation Therapy / Q000295:instrumentation / Q000379:methods*; D004566:Electrodes; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008564:Membrane Potentials; D009119:Muscle Contraction; D053580:Muscle Strength; D010865:Pilot Projects; D052097:Quadriceps Muscle / Q000294:innervation*