Abstract
Liao, T.-J. and Nishikawa, H. The Variation of Action Potential and Impedance in Human Skeletal Muscle during Voluntary Contraction. Tohoku J. Exp. Med., 1994, 173 (3), 303-309-We used an insulated acupuncture needle to deliver a 20kHz alternative current to detect the changes on the electromyogram (EMG) and deep muscle impedance. We found that impedance increased (with a duration of 224.1±75.3msec) and then decreased (with a duration of 293.4±97.3 msec) after motor unit action potential (MUAP) firing during isometric voluntary contraction (VC) of the tibialis anterior muscle (TAM). We divided the positive peak into pattern I (with a latency range of ≥30cosec and ≤75msec) and pattern II (with a latency range of >75msec and ≤140msec). These patterns of change corresponded to the contraction times of tension caused by the electrical stimulation and VC. These impedance changes may be caused by a change in the extracellular and intracellular fractions, and may reflect the variance of tension intensity in the muscle tissue.
