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.

Tolerance and Physiological Correlates of Neuromuscular Electrical Stimulation in COPD: A Pilot Study

“…Electrically-induced leg muscle fatigue [12] could increase leg discomfort during training and reduce tolerance to NMES. Subcutaneous body fat constitutes a resistance to electrical current in such a way that increasing current intensities may be more challenging in lean patients [13]. Finally, it is possible that the occurrence of a systemic inflammatory response following electrical stimulation could influence the tolerance to NMES but this has yet to be investigated.…”

Skin Moisture and Heat Transfer

“…These include neuronal transmission [ 91,123 ] , pulmonary vascular remodeling [ 111 ] , arterial sclerosis [ 86 ] , and exercise-induced cardiac protection [ 105 ] . Impaired production or bioavailability of nitric oxide leads to endothelial dysfunction and is the root cause of much different cardiovascular pathology including diabetes, hypertension, heart failure, and coronary artery disease [ 92 ] .…”

Differences in current amplitude evoking leg extension in individuals with spinal cord injury

“…Several research studies have investigated factors that affect the distribution of current propagation during electrical stimulation of the knee extensor muscle group [11][12][13][14][15][16][17][19][20][21][22]. It is recognized that increasing the current amplitude may lead to increases in both skeletal muscle motor unit recruitment and evoked torque in a linear pattern [11,14].…”

“…Maffliuletti et al studied sex-specific response to current distribution and showed that women require lower current amplitude to activate both sensory and motor responses compared to men [15]. This suggests that fat thickness may impact the distribution of current to target skeletal muscle [15,[19][20][21][22]. Leg extension exercise in conjunction with weight lifting has been shown to evoke significant skeletal muscle hypertrophy after SCI [4,9,10].…”