Use of Neuromuscular Electrical Stimulation to Elicit Muscle Contractions Does Not Impair the Hyperemic Response Compared to Volitional Contractions.

Abstract

Electrical stimulation-induced muscle contractions in individuals with paralyzed muscles are often associated with early-onset fatigue. We examined whether electrical stimulation of the quadriceps muscle results in vasoconstriction and a reduction in blood flow, which may contribute to this early-onset fatigue. Seventeen young individuals completed 40 electrical stimulation isometric contractions (stimulation frequency of 75 Hz, pulse duration of 400 μs, on-off ratio 6.0-20 secs) and force matched voluntary isometric contractions. Isometric force, heart rate, blood pressure, superficial femoral diameter, and blood velocity were measured at baseline and during exercise (contractions 1, 5, 10, 15, 20, 25, 30, 35, and 40). Net, antegrade, and retrograde blood flow, and conductance were quantified. Two-way, within-subjects analyses of variance were used to evaluate diameter, blood flow, and conductance. Diameter was not different between electrical stimulation and voluntary (P = 0.57). Net blood flow increased during both conditions with the greatest blood flow occurring during electrical stimulation compared to voluntary (P ≤ 0.01). Electrical stimulation showed a greater increase antegrade and reduced retrograde flow compared to voluntary. After the twentieth contraction, electrical stimulation also elicited greater conductance than voluntary (P ≤ 0.049). The use of neuromuscular electrical stimulation to elicit muscle contractions does not result in vasoconstriction or a reduced hyperemic response compared to volitional contractions.